Midbrain Atrophy in Parkinson’s, Alzheimer’s and Multiple Sclerosis

Brain-sagittal-GraysThe midbrain is the smallest structure in the brain and is positioned on top of the brainstem. In the picture to the right, it can be seen located between the thalamus and hypothalamus of the diencephalon above, and the pons and medulla of the lower brainstem below. The thalamus located on top of the midbrain, forms the walls of the third ventricle. Among other things, atrophy of the thalamus and enlargement of the third ventricle (ventriculomegaly) have been associated with multiple sclerosis (MS).

In contrast to the ventricles, which are in the core of the brain, the cisterns surround the midbrain. Enlargement of either can be a sign of atrophy. Enlargement of the cisterns along with atrophy of the midbrain has been associated with variations of Parkinson’s called progressive supranuclear palsy, vascular Parkinson’s, vascular dementia, multisystem atrophy, and an Alzheimer’s variation called Lewy-body dementia.

Some of the characteristics of vascular Parkinson’s and vascular dementia overlap. Both conditions are associated with a more frequent occurrence of brain atrophy, white matter lesions and a predominance of motor symptoms, such as gait disturbances. Several clinical features of vascular Parkinson’s, including early postural instability, pseudobulbar phenomena, and predominance of lower body signs, further suggest that vascular Parkinson’s may be associated with atrophy of the brainstem.

In addition to the neurodegenerative conditons above, atrophy of the midbrain has also been associated with MS. More often, however, MS is associated with enlargement of the cerebral aqueduct of the ventricular system, especially the upper portion located adjacent to the third ventricle, mentioned above. In any case, researchers now suspect that the midbrain is particularly sensitive to neurodegenerative conditions. They offer no explanation, however, as to why it is particularly sensitive. One possible explanation, may be because of its exposure to cerebrospinal fluid (CSF) hydraulics in the ventricular system and cisterns.

The midbrain is surrounded by cisterns filled with CSF. CSF also passes from the third ventricle through the cerebral aqueduct in the midbrain to the fourth ventricle below. The portion of the midbrain located behind the aqueduct is called the tectum. The portion in front is called the tegmentum. The midbrain is associated with sight, sound, motor control, the sleep-wake cycle, alertness and temperature regulation. It also contains pathways for communication and coordination between the higher and lower centers of the brain, brainstem and spinal cord including the long motor tracts that descend to the cord to supply the muscles and the sensory nerves that deliver information from receptors in the body to appropriate centers in the brain.

midbrain-axialAs shown in the sketch of the midbrain on the left, the cerebral aqueduct is surrounded by gray unmyelinated nerves called the periaqueductal gray matter, which contains the reticular formation of the brainstem. The reticular formation contains functional cell groups that are important for control of eye, head, or lid movements. The mesencephalic reticular formation is primarily involved in the control of vertical gaze. Vertical gaze is sometimes affected in Parkinson’s disease and MS. The dark gray band on the ventral (front) side of the midbrain is the substantia nigra which produces a neurotransmitter called dopamine. Atrophy of the substantia nigra and decreased dopamine production are hallmark signs of primary Parkinson’s disease. Among other things, decreased dopamine production causes resting tremors in Parkinson’s.

There are many different types of midbrain syndromes. Two well known midbrain syndromes, called Parinaud’s syndrome and dorsal midbrain syndromes, have been associated with Parkinson’s disease, dementia and MS. Dorsal midbrain syndromes are associated with difficulty looking up, diplopia, blurred vision, oscillopsia (symmetrical eye tremors), as well as other accompanying neurological symptoms. It is sporadic. The causes are obstructive hydrocephalus, hemorrhages in the midbrain, MS, AV malformations, trauma, and compression, such as from pineal tumors.

Hummingbird-sign2-radiopaediaAtrophy of the midbrain is most commonly associated with progressive supranuclear palsy, mentioned above. The atrophy causes a characteristic deformation of the midbrain that radiologists refer to as the hummingbird sign when viewed from the sagittal view (side) because it looks like a small bird with a large beak, as seen in the brain scan on the left. The brain scans on the left and below are used with permission from a collection by Dr. Frank Gaillard of Radiopaedia.com. The hummingbird shape is seen at the top portion of the long, dark gray structure (brain stem) in the middle of the brain. There is a long, thin, curved beak-like projection in front and a big round structure below, which is the pons portion of the brainstem. The hummingbird sign is also called the penguin sign. In either case, the beak is the most telling feature of atrophy of the midbrain. The beak is part of the tectum on the dorsal (rear) surface of the midbrain. The tectum contains important nerve centers related to the control of eye muscles and sight. It also contains nerve centers related to sound.

When viewed from top to Mickey-mouse-signbottom looking down on the brain, which is called an axial view, the midbrain appears compressed front to back in a characteristic deformation. Radiologists call it the Mickey Mouse sign because it looks like a small round face with a little black nose and big round ears located in the center of the MRI on the right.

Progressive supranuclear palsy, also known as Steele-Richardson-Olszewski syndrome, is a rare disease. It gradually destroys nerve cells in parts of the brain that control eye movements, breathing, and muscle coordination. The loss of nerve cells causes palsy, or paralysis, that slowly gets worse as the disease progresses. The palsy affects the ability to move the eyes, relax the muscles, and control balance. The initial symptoms in two-thirds of the cases are loss of balance, lunging forward when mobilizing, fast walking, bumping into objects or people, and falls. Other common early symptoms are changes in personality, general slowing of movement, and visual symptoms.

Signs of progressive supranuclear palsy include: supranuclear ophthalmoplegia, rigid neck spasms called dystonia, Parkinsonism signs and symptoms, pseudobulbar palsy (difficulty swallowing and speaking), behavioral and cognitive impairment, imbalance and difficulties walking, as well as frequent falls. Atrophy of the midbrain appears to be more characteristic of vascular Parkinson’s and progressive supranuclar palsy than primary Parkinson’s which is typically associated with specific degeneration and atrophy of the substantia nigra. It’s also less severe in vascular Parkinson’s compared to progressive supranuclear palsy.

The cause of atrophy of the midbrain in Alzheimer’s and Parkinson’s disease, as well as enlargement of the cerebral aqueduct of Slyvius in MS is unknown. In addition to the aqueduct, MS is also associated with enlargement of the third ventricle that adjoins and drains into it. Ventriculomegaly and an enlarged cerebral aqueduct are signs of hydrocephalus. In contrast to the ventricles and cerebral aqueduct, enlarged cisterns are not necessarily a sign of hydroceplalus if not accompanied by enlargement of the ventricles. On the other hand, hydrocephalus is caused by obstruction to CSF flow that results in an increase in volume. One of the most likely places for blockage of CSF flow to occur is in the foramen magnum and upper cervical spinal canal. Blockage of CSF flow between the cranial vault and spinal canal can cause an increase in volume in the cisterns and subsequent compression of structures they surround such as the midbrain. Decreased blood flow and chronic ischemia may also play a role in atrophy of the midbrain but that’s another topic that will be discussed in future posts. In any case, malformations, misalignments and chronic deformation of the upper cervical spine may affect blood and CSF flow in the brain leading to chronic ischemia, edema and normal pressure hydrocephalus resulting in neurodegenerative conditions and diseases.

For further information on the role of the midbrain in neurodegenerative conditions, visit my website at www.upright-health.com. The cause behind many of the conditions above is discussed in my book, “The Downside of Upright Posture”. Information, of which, can also be found at the website.

Posted in Alzheimer's, diplopia, multiple sclerosis, nystagmus, Parinaud's syndrome, Parkinson's, progressive supranuclear palsy | Tagged , , , , , , | 23 Comments

Dissociation of CSF Flow in Neurodegenerative Diseases

One of the suspected causes of hydrocephalus, associated with neurodegenerative diseases seen in children and adults, is a dissociation of cerebrospinal fluid (CSF) flow between the cranial vault and spinal canal. The term hydrocephalus means water on the brain. Hydrocephalus causes the ventricles to enlarge, which is called ventriculomegaly. The ventricles are chambers in the brain where CSF is produced. Ventriculomegaly can be caused by anything that obstructs the pathways and normal flow of CSF, or it can be caused by inadequate absorption of CSF described below. In children, hydrocephalus is associated with high presssure in the brain called intracranial pressure. The high intracranial pressure, however, may be due to the open joints of the skull in a child, which provide less resistance to CSF pressure. The combination of high intracranial pressure and open joints in the skull causes the head to enlarge.

Normal pressure hydrocephalus (NPH) is a condition seen in adults in which the CSF volume increases and the ventricles enlarge but intracranial pressure remains normal or just slightly elevated. The size of the head, likewise, remains normal due to the closed joints of the skull. More than likely, the closed joints of the adult skull act like a counter-weight on a pressure cooker and limit CSF pressure inside the cranial vault. This will be discussed further in future posts. NPH and ventriculomegaly in adults can be caused by conditions such as traumatic brain injuries, subarachnoid hemorrhage (bleeding), prior intracranial surgery, and meningitis (inflammation of the protective coats called meninges). Most cases of NPH, however, are unknown.

The brain scan on the right is of an adult patient with NPH. NPH is typically associated with ventriculomegaly without atrophy (shrinkage) of the brain. Atrophy is seen as a widening of the spaces of the brain called fissures and sulci (dark spaces between the folds in the picture) that separate the gyri and folds of the different lobes. Ventriculomegaly is usually found around the frontal and temporal horns of the lateral ventricles.

In adults, NPH and enlarged lateral ventricles have been associated with Alzheimer’s and Parkinson’s disease, as well as dementia, schizophrenia, bipolar disorder, Parkinson’s Plus, Huntington’s disease and other neurodegenerative conditions for decades. More recently, enlargement of the third ventricle has been associated with multiple sclerosis. The fourth ventricle is sometimes enlarged in a condition called multisystem atrophy (MSA), which is a variant of Parkinson’s disease. MSA will be discussed further below.

In the brain scan above, the black arrows point to the lateral ventricles, which are seen as the large black spaces in the core of the brain. The ventricles are part of the brain. They are surrounded by the lobes, diencephalon (thalamus and hypothalamus) and brainstem and contain CSF. The corpus callosum forms the roof of the lateral ventricles and is seen as the white rim over the black space. The white rim below the lateral ventricles is called the fornix which sits over the roof of the third ventricle. As in this case, NPH often causes the corpus callosum to bow upward, and compress the outer cortex of the brain against the inner surface of the skull. White matter lesions are often present in the periventricular areas that surround the lateral ventricles. Periventricular white matter lesions are also seen in MS.

CSF flows from the lateral ventricles into the third and then the fourth ventricle. After leaving the fourth ventricle CSF flows into the cisterns. The cisterns are not part of the body of the brain called the parenchyma.  Instead, they are part of the subarachnoid space that surrounds the brain. The subarachnoid space is a network of tunnels formed in the protective outer coats of the brain called meninges. The cisterns are seen in the brain scan above as the black spaces located around the brainstem and beneath the cerebellum (cauliflower-like structure in the lower rear of the skull). In this particular case, the fourth ventricle, seen in front of the cerebellum, is enlarged as is the space below it which is called the cisterna magna. The white arrow points to the cerebral aqueduct which is also enlarged. The cerebral aqueduct is a canal that connects the third ventricle to the fourth ventricle. The third ventricle is the dark space beneath the lateral ventricles. Some researchers now suggest that the term hydrocephalus should include an increase in CSF volume outside the ventricles as well, such as in the cisterns and the subarachnoid spaces.

Multisystem-atrophyCSF from the fourth ventricle drains into the pontine cistern, the cisterna magna and the central canal of the spinal cord. The pontine cistern is the black space in front of the brainstem (the long white structure). The pons is the part of the brainstem that sticks out toward the face like a big round potbelly.  The cisterna magna is the black space beneath the cerebellum.

The central canal of the cord is not seen in this image. The connection between the fourth ventricle and the central canal will be covered separately as it relates to a type of hydrocephalus in the cord called hydromyelia or syringomyelia. Sometimes they are simply referred to as a syrinx. For now suffice it to say, they are abnormal cavities in the cord that are probably caused by pressure problems within the cord, similar to hydrocephalus which is due to pressure problems in the brain.

After entering the cisterns, CSF can flow down into the subarachnoid space of the spinal cord or it can flow upward through the subarachnoid space of the brain to the arachnoid granulations at the top of the brain, where the bulk of CSF absorption takes place to eventually leave the central nervous system via the venous system. The arachnoid granulations are one-way valves that connect the subarachnoid space to the superior sagittal sinus. The superior sagittal sinus is part of the venous drainage system of the brain located at the top of the skull.

The MRI above on the left is of a patient with a condition called multisystem atrophy. Multisystem atrophy is a variant of Parkinson’s disease, which also includes olivopontocerebellar atrophy. It is also known as Shy-Drager Syndrome. Among other things, multisystem atrophy is associated with dysautonomia and orthostatic hypotension in which blood pressure drops when changing position from sitting to standing. Dysautonomia is a malfunction of the autonomic nervous system that controls automatic internal operations such as heartbeat, circulation, respiration, temperature regulation, bladder and bowel control and more. In addition to Parkinson’s and multisystem atrophy, signs and symptoms of dysautonomia are common in Alzheimer’s disease and multiple sclerosis.

As can be seen in the brain scan above, in addition to enlargement of the fourth ventricle, multisystem atrophy is also associated with enlargement of the cisterns that surround, cushion and support the brainstem and cerebellum. In this regard, it looks similar to the MRI in the case with NPH at the top of the page. The difference is, the lateral ventricles aren’t enlarged. On the other hand, NPH is more typically associated with enlarged lateral ventricles but not enlarged cisterns. In this case the front of the pons (potbelly) appears slightly compressed due to the enlargement of the pontine cistern.

DandyWalker SyndromeThe brain scan on the right is of a child with a condition called Dandy-Walker Syndrome, which looks somewhat similar to the multisystem atrophy scan above. Here the fourth ventricle (the dark space in front of the cerebellum) and the prepontine cistern (the dark space in front of the cord) aren’t enlarged as above. Only the cisterna magna below the cerebellum is enlarged, which is called mega cisterna magna. Some cases of Dandy-Walker syndrome have enlarged ventricles, hydrocephalus and a mega cisterna magna. According to the classic definition, a mega cisterna magna alone, without ventriculomegaly, isn’t classified as hydrocephalus.

The enlarged cisterns and fourth ventricle seen in MSA (Parkinson’s) in adults, and in Dandy-Walker Syndrome in children are usually attributed to atrophy of the brainstem and cerebellum, which are surrounded by cisterns.  Likewise, ventriculomegaly seen in neurodegenerative diseases such as Alzheimer’s, Parkinson’s and multiple sclerosis is typically attributed to atrophy of periventricular structures that surround the ventricles. Ventriculomegaly seen in NPH, on the other hand, is typically attributed to enlargement of the ventricles without atrophy of the surrounding tissues and structures. The problem is, the ventricles don’t always return to normal size when excess CSF volume is surgically decreased with a shunt. This led researchers to suggest that, the sustained enlargement of the ventricles may be due to permanent damage to the surrounding periventricular structures as a result of the NPH.

There are two primary theories regarding the origin of NPH. The first theory has to do with obstruction of CSF flow or blockage of resorption into the venous drainage system of the brain discussed above. The other theory is that NPH is due to atrophy of surrounding structures, such as the periventricular white matter that gets strained and tensioned to the point of breaking, causing the walls of the ventricles to weaken and enlarge. Enlargement of the ventricles also stretches, strains and compresses surrounding blood vessels that can decrease blood flow and cause ischemic tissue damage. In either case, the subsequent weakness in the walls of the ventricles and surrounding structures cause the ventricles to enlarge. NPH, in turn, increases tension, tangential and shear stresses in the brain, as well as compression loads caused by expansion and contraction of the brain with each beat of the heart that forces a relatively large volume of fluid into the mostly closed container of the cranial vault.

There is a reason why these different types of ventriculomegaly (hydrocephalus) and mega cisterns seen in children and adults look remarkably similar. It is because they are all related to faulty CSF flow in the brain. Whether it shows up as ventriculomegaly or mega cisterns depends on the location of the obstruction or malabsorption problem. Aside from internal problems in CSF pathways of the brain inside the cranial vault, researchers now suspect that one of the causes of hydrocephalus in children and adults is a dissociation of CSF flow between the cranial vault and spinal canal. Dissociation simply means that the normal flow between the two compartments is disrupted, and as a result they react independantly. Among other things, this can cause potentially destructive abnormal increases in CSF pressure waves in the brain and cord. Dissociation of CSF flow between the two compartments may similarly play a role in hydromyelia and other conditions of the cord.

Upright posture requires proper CSF flow between the cranial and spinal compartments in order to maintain the correct volume, pressure, protection and bouyancy of the brain. Excess CSF volume in the ventricles, cisterns and subarachnoid spaces can cause destructive tension (stretch) and compression loads in the brain. An insufficient volume reduces bouyancy, which causes the brain to sink and make contact with the base of the skull. The connection between the cranial compartment and spinal compartment is in the upper cervical spine. Malformations, injuries and misalignments of the upper cervical spine can cause a dissociation of CSF flow between the cranial and spinal compartment. Further below in the lower spine, spondylosis (degeneration), scoliosis (abnormal curvature) and stenosis (narrowing) alter the design of the spinal canal and thus affect blood and CSF flow. The changes in the design of the spinal canal can, likewise, result in a dissociation of CSF flow between the cranial vault and spinal canal. Thus far, the studies on dissociation of CSF flow between the cranial vault and spinal canal have all been done using supine MRI. Future research will need to be done using upright MRI. Upright MRI will most likely reveal much more about the destructive consequences of dissociation of CSF flow between the cranial vault and spinal canal.

The areas hardest hit by faulty fluid mechanics in the cranial vault are: 1) the periventricular structures that surround the ventricles, 2) the bottom surfaces of the brain, brainstem and cerebellum located above the base of the skull that are surrounded and supported by the cisterns, and 3) the cortex of the brain closest to the inner surface of the skull. The particular areas that are affected are determined by the cause and the consequences of the faulty CSF flow.

For more information on this and other related subjects visit my website at www.upright-health.com.

Posted in Alzheimer's, Dandy-Walker syndrome, multiple sclerosis, multisystem atrophy, Parkinson's | Tagged , , , , , | 6 Comments

Hydrofracking, Ventriculomegaly and Brain Atrophy

Researchers suspect that enlarged ventricles, known as ventriculomegaly,  seen in many neurodegenerative diseases may be the result of atrophy (decrease in size) of the brain. The cause of the damage or atrophy of the brain may be due to destructive waves and hydraulic pressures that damage tissues by a process I compare to hydrofracking which is used by engineers to fracture rocks. Ventriculomegaly and brain atrophy have been associated with Alzheimer’s disease, Parkinson’s disease and its variants, called Parkinson’s Plus, as well as multiple sclerosis, amyotrophic lateral sclerosis and Huntington’s disease.

The picture above shows the left half of the brain. The face would be to the right. The cauliflower structure in the lower left corner is the cerebellum. The hollow area (darker grey) in the middle of the brain is the left lateral ventricle. The heavy white structure that forms the roof over the lateral ventricle is the corpus callosum. The heavy white structure that forms the floor is the fornix. The corpus callosum is a group of myelinated (white matter)  high speed interconnecting communication pathways that link the left and right halves of the brain. The fornix is, likewise, a high-speed communication pathway of white fibers. The third ventricle is located just below the fornix. The fourth ventricle is the space shaped like a dart between the cerebellum and brainstem. The ventricles are chambers in the core of the brain and brainstem where cerebrospinal fluid (CSF) is produced.

CFS is basically water with some sugar and a few other ingredients mixed in. CSF fills the ventricles and surrounds the entire brain in a water jacket. CSF in the ventricles, fissures and spaces of the brain serves to cushion and protect the brain from compression against the bones of the cranial vault, as well as maintain its shape, layout and position inside the vault. It also serves as the lymphatic waste removal system of the brain. Due to the constant state of tension caused by CSF in the ventricles and spaces in and around the brain, some engineers consider the brain to be essentially a non-compressible monophasic structure. Monophasic simply means that it doesn’t buckle and deform under pressure.

In contrast to engineers, chiropractic and osteopathic craniosacral theories have maintained for many years that the musculoskeletal system, CSF and central nervous system, which includes the brain and spinal cord, rhythmically pulsate and move. The movement and pulsations are driven by neurological, cardiovascular and respiratory waves. More recently, radiologists have similarly shown that CSF pulsates and that the ventricles expand and contract in synchrony with cardiovascular waves. They have also shown that the brain moves up and down like a piston during each cardiac cycle. This is because the increase in volume, mass and pressure of the brain caused by the increase in blood volume drives the brain downward in the cranial vault. Relaxation of the heart relieves the pressure and strain, which causes the brain to rise inside the vault. This expansion and contraction coupled with up and down movement of the brain inside the vault makes it a biphasic structure in engineering terms and futher confirms the craniosacral theory.

The picture below is from an article published in 2011 in the Delaware Free Media News on the politically controversial process called hydrofracking. Hydrofracking is done by pumping water under pressure into rocks located deep below the surface of the earth to open their fissures (cracks) and pores by fracturing them. The process is mostly used to flush out oils and gases to be brought to the surface and refined. In addition to the potential pollution of water aquifers that are located above the fracture zone, the compression and shear stress caused by hydrofracking can set off vibrational waves deep below in the fracture zone that travel to the surface where they can be felt as earthquakes by residents. The earthquakes can cause tears in the surface of the earth and cracks in buildings.

fracking-graphic

A similar situation can occur inside the cranial vault of the skull due to the heart pumping a relatively large volume of blood with each contraction, into the mostly closed container of the cranial vault. If the blood volume and pressure coming into the cranial vault isn’t sufficiently buffered (within the subarachnoid space shown below) before it enters the brain, strong pressure waves can be sent into the core of the brain. These high pressure waves can damage delicate tissues resulting in atrophy and subsequent ventriculomegaly. The structures that most often show atrophy are often located in the periventricular areas, the areas that surround the ventricles.

Aside from atrophy, some cases of ventriculomegaly are caused by an increase in CSF volume due to obstruction or faulty flow. In these cases, the ventricles and brain return to normal size when flow is restored via shunts and surgery due to their biphasic nature. While these cases are seen much less frequently thus far, early detection may change things and prevent permanent damage and subsequent atrophy.

In addition to unchecked incoming high pressure arterial waves causing problems, damage can also occur to periventricular structures due to overstretching similar to an overinflated balloon. At the same time, the expanding ventricles can compress neighboring structures and blood vessels. Compression of blood vessels can decrease blood flow in smaller blood vessels resulting in chronic ischemia and subsequent atrophy. Some researchers further suspect that faulty CSF flow may cause water hammers(explained below) in the brain similar to tremors and earthquakes caused by hydrofracking. Water hammers can similarly fracture surrounding tissues resulting in atrophy.  In any case, the cause of the ventriculomegaly and atrophy can come from water pressure problems inside the ventricles or outside  of them.

subarachnoid-perivasularIn contrast to hydrofracking which pumps large volumes of water into deep subterranean rocks, the heart pumps a relatively large volume of blood into the arteries contained within the subarachnoid space (see picture to the right). The subarachnoid space surrounds the outer surfaces of the lobes, the convolutions (gyri) and fissures of the brain and the brainstem within the cranial vault. The large incoming arteries pass through the subarachnoid space to supply numerous smaller branches (arterioles) that exit the subarachnoid space and enter tunnels called perivascular or Verchow-Robin spaces to supply smaller branches that supply the parenchyma (substance) of the brain.

As stated above, the periventricular areas are those structures that interface with the ventricles.  These are important nerve centers. Blood vessels also pass through the periventricular space between the ventricles and surrounding structures. As you can see in the picture of the brain at the top of the page, arteries pass over the lateral ventricles. Veins also pass over the lateral ventricles. Smaller arteries and veins are similarly located next to the third and fourth ventricle. In contrast to the veins on the surface of the brain, the periventricular veins are much smaller and more susceptible to compression. Smaller arterioles can, likewise, be compressed.

The stress from the increase in blood volume causes mechanical strains and temporary deformation of the brain as the subarachnoid space balloons slightly outward. In cases of high intracranial pressure, the areas of the subarachnoid space located near the bones of the cranial vault can compress surface veins of the brain against the bones of the vault and, thereby, decrease blood flow. Ballooning of the subarachnoid space also causes compression loads on the lobes of the brain and the ventricles similar to squeezing a sponge. Due to their location in the core of the brain, the periventricular areas are the most vulnerable to compression and shear stresses.

In addition to compression loads caused by enlargement of the subarachnoid space and ventricles, ventriculomegaly also causes shear stresses due to stretching of the periventricular structures and blood vessels. The combination of excess compression and shear stresses can, over time, cause mechanical damage to the structures and blood vessels, as well as decrease blood flow that can result in tissue atrophy (shrinkage).

The rhythmical beating of the heart thus causes pulsations and pressure waves to form in the brain, blood and CSF.  Those pulsating hydraulic waves dissipate through the entire brain. If the pressure isn’t reduced appropriately, the high pressure arterial waves on the surface of the brain get directed inward toward the weaker more vulnerable parts of the brain, such as those surrounding the ventricles in the periventricular areas. These structures get compressed against the unyielding walls of the cranial vault on the outside and the stiff walls of the ventricles in the center of the brain that are supported by internal tension from CSF pressure. Chronic pulsatile high pressure waves can lead to hydraulic fracturing of vulnerable tissues. This can result in degeneration and atrophy of surrounding periventricular structures. Some researchers suspect that myelinated nerves (white matter) such as those that surround the ventricles, are more vulnerable to tension strains and subsequently more likely to tear (fracture) from excess loads.

In a healthy brain, the subarachnoid space typically buffers the increase in blood volume and pressure. Most of the force is absorbed by veins in the subarachnoid space which have weak walls and are easily compressible. Compression of the veins moves blood out of the brain reducing pressureby removing volume inside the cranial vault. Pressure is further relieved by squeezing a proportionate amount of venous blood and CSF out of the brain and cranial vault by way of the foramen magnum, which is the large hole in the base of the skull for the passage of the brainstem and cord. As the arterioles relax following contraction of the heart, and the arteries and veins begin to return to their previous size, the fresh supply of arterial blood in the subarachnoid space is released into the perivascular spaces of the brain under lower pressure.

Blockage of venous blood and cerebrospinal fluid anywhere along their pathways can alter CSF flow and cause abnormal pressure waves. The abnormal pressure waves are the result of incoming arterial blood flow and pressure waves running into resistance from venous backpressure and reduced or blocked CSF outflow causing what plumbers refer to as a water hammer. As shown in the sketch on the left, water hammers occur in domestic plumbing when water flow out of a faucet is suddenly shut off. This causes waves to be reflected backwards and crash with incoming waves. Since stiff non-elastic pipes can’t absorb the force like elastic veins, it causes them to shudder like a tremor. The tremor causes the pipes to bounce on surrounding structures resulting in noises that sound like someone hammering on the pipes.

Alzheimer’s and other neurodegenerative diseases seen in adults are often associated with normal pressure hydrocephalus (NPH) in which the ventricles enlarge but CSF pressure remains normal or just slightly elevated.  To this day, it remains a mystery to scientists as to how the ventricles can enlarge when CSF pressure is normal. The only plausible explanation so far is atrophy. In other words, the brain decreases in size around the ventricles creating space allowing the ventricles to enlarge when CSF moves into the ventricles.

Some researchers suspect that brain atrophy is caused by water hammers that damage susceptible tissues. Others suggest that it is due to compression and shear stresses mentioned previously. Still others suggest that compression and shear forces can damage blood vessels and decrease flow resulting in atrophy.  Lastly, some cases are due to an increase in CSF volume due to faulty flow without atrophy. In other words, the brain is simply compressed and returns to normal size when CSF flow and volume are restored as mentioned above.

In brief, the biphasic brain is trapped between a rock and a hard place. The rock is the skull that surrounds and protects it. The hard places are the ventricles located in its core, as well as the surrounding spaces, filled with CSF. Shear stresses caused by stretching from ventriculomegaly strain the periventricular tissues. Increases in arterial blood volume during heart contractions cause compression load strains that deform the brain and ventricles. Abnormally high blood and CSF pressure waves coupled with water hammers compound the internal and external ventricular stresses and strains with tremors. Over time, strong chronic tremors can tear tissues.

Researchers are now looking into the impact of blockage of the venous drainage system of the brain and abnormal CSF pulse waves. Over time, chronic venous drainage problems and high CSF pressure waves can lead to hydrofracking, ventriculomegaly and atrophy of the brain. One of the most likely points of blockage to venous blood and CSF flow is in the cervical spine, especially the upper cervical spine. The most vulnerable structures to hydrofracking and subsequent atrophy are located in the periventricular areas that interface with the lobes of the brain.

For additional information on these and related topics visit my website at www.upright-health.com.

Posted in Alzheimer's, chiari malformations, Dandy-Walker syndrome, multiple sclerosis, Parkinson's | 6 Comments

Ventriculomegaly and Mega Cisterns in Alzheimer’s, Parkinsons and MS

About seventy years ago, a highly regarded neurosurgeon from Columbia, Dr. Solomon Hakim, noticed that on autopsy many patients with Alzheimer’s disease had enlargement of the ventricles without destruction of the outer cortex of the brain, which would have happened if the enlargement was due to high pressure. The ventricles are chambers in the center of the brain and brainstem where a watery substance called cerebrospinal fluid (CSF) is produced.  The purpose of CSF is to support and protect the brain. It also removes waste from the brain. Enlargement of the ventricles is called ventriculomegaly. Ventriculomegaly seen on brain scans is a sign of hydrocephalus, which is an increase in CSF volume in the brain.

Ventriculomegaly stretches and deforms the surrounding periventricular structures. Prolonged deformation can lead to plastic deformation, which is permanent.  Ventriculomegaly also compresses the veins, that are located on the outer surface of the brain, against the bones of the cranial vault. This can decrease venous drainage of the brain and cause the hydrocephalic condition to worsen. Ventriculomegaly and damage to periventricular structures may play a role in many of the signs and symptoms associated with neurodegenerative diseases such as motor weaknesses, dementia, cog fog, heat intolerance, sleep disturbances, sleep apnea and incontinence of the bowel and bladder.

Dr. Hakim later called the condition he discovered normal pressure hydrocephalus (NPH). He also made a major improvement in the design of the spring on the valves that are used in shunts to treat hydrocephalus. The principle behind his modification to shunts is still in use today.

In 1976 Dr. Hakim published a paper in which he compared the brain to a sponge and suggested that poroelasticity plays a role in the development of ventriculomegaly. The term poroelasticity comes from engineering sciences related to soils and rocks and will be explained later in this post. Since the advent of brain scans, ventriculomegaly has been associated with Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, and other neurodegenerative conditions. Mega cisterns are enlarged CSF chambers similar to ventriculomegaly and will also be discussed in this post.

In the brain scan below, the lateral ventricles are located beneath the large white arch-like structure. A smaller arch-like white band underneath the larger structure is joined to it  in the rear and is the bottom of the lateral ventricle. The third ventricle is below the lower white band and above the midbrain which is the uppermost part of the brainstem (stalk-like). The fourth ventricle is the dart shaped area between the brainstem in front and a cauliflower-like looking structure in the rear, which is the cerebellum.

The dark gray spaces in front of the brainstem and beneath the cerebellum are called cisterns. CSF flows out of the fourth ventricle and into the cisterns. The cisterns cushion the brain from the hard walls of the cranial vault. They also support the brain and prevent it from sinking into the large hole in the bottom of the vault called the foramen magnum. This is the opening for the passage of the brainstem and spinal cord, as well as blood vessels and CSF pathways.

Ventriculomegaly can be caused by an increase in CSF volume and pressure in the ventricles, or it can be caused by atrophy (shrinking) of the brain due to degeneration of the structures that surround them. It can also be a combination of atrophy and changes in CSF volume and pressure. In many cases the cause of the ventriculomegaly is unknown. In any case, enlargement of the ventricles can affect the important structures that surround them in what is called the periventricular areas.

The periventricular structures that surround the ventricles are some of the most important and fundamental systems in the brain such as the limbic (reptilian/visceral/self-preservation) and autonomic (vegetative) nervous systems. The roof of the lateral ventricles is formed by a large group of myelinated (white matter) nerves that link the left and right hemispheres of the brain. Descending long myelinated motor (muscle) nerve tracts called the internal capsule pass close to the ventricles.

To get a better understanding of the mechanical forces that can cause enlargement of the ventricles, researchers have been turning to engineers, mathematicians and physicists for answers. From an engineering perspective, the skull and brain, as well as the fluids inside them can be compared to rocks and soils. Poroelasticity is a property of rocks and soils that affect their structural strength and their abiltiy to support large loads such as from water, waves, buildings, bridges and roads. Different types of rocks and soils, as well as the shapes of their pores, fissures, fractures and caves affect the way they handle loads.  Similarly, poroelasticity affects the structural strength and shape of the brain, as well as deformation such as ventriculomegaly. This is important because deformation of the brain such as enlarged ventricles can damage nearby delicate nerves and blood vessels. Damage to nerves and blood vessels can, in turn, lead to atrophy (shrinkage) and ventriculomegaly.

The term poroelasticity refers to the pores in soils and rocks that affect their elasticity. Elasticity is the ability of a structure to deform and return to its original shape without breaking (fracturing). The pores in soils and rocks can be filled with gas or fluids. The gas could be air or natural gas. The fluid could be water or oil. The gases or fluids affect the strength of soils and rocks, as well as their elasticity. Consequently, the gases and fluids affect the ability of soils and rocks to deform and reform. Structures that go through expansion and contraction are considered to be biphasic. If it can’t deform and reform, meaning return to its original shape, the structure is considered to be monophasic. The ability of a structure to deform and return to its original shape is determined by, what is called, its elastic coefficient.

As far as biphasic poroelastic properties are concerned, blood and CSF are essentially non-porous and non-compressible. They also lack elastic properties. Instead, they have viscoelastic properties that are entirely different. Basically, elasticity is a property of solid structures. Viscoelasticity refers to properties of liquids and foams such as viscoelastic memory foam mattresses used for sleep surfaces. In contrast to blood and CSF, the brain is made of billions of cells that are filled with fluids called intracellular fluids. The brain’s many fissures, sulci, interstitial spaces, perivascular spaces, subarachnoid spaces, ventricles, caverns, cisterns and sinuses are all filled with fluids such as, intracellular fluids, interstitial fluids, blood and CSF. This makes the brain a highly porous liquid filled structure.

In addition to being porous, the brain is also elastic. For example, tumors and hydrocephalus can cause significant deformation of the brain. When the stress is removed, however, it returns to normal size provided permanent damage has not yet occurred. Being elastic technically makes the brain a biphasic structure capable of expansion and contraction. Under normal circumstances, however, the brain is only slightly biphasic. This is because it is completely surrounded and all it spaces are filled with CSF. CSF pressure causes internal and external tension, called turgor, in the pores and spaces of the brain. Turgor causes stiffness.

The stiffness caused by turgor is important to maintaining the shapes of living things. Plants use turgor to stay upright. If they become dehydrated they quickly start to droop. Cells similarly use turgor to maintain their structure and internal space and prevent compression. Turgor, likewise, maintains the shape of the brain. Maintaining the shape of the brain is important because it prevents compression of delicate nerve structures and smaller blood vessels that travel through sulci (folds), fissures (cracks) and foramen (holes) in the brain and skull. Turgor also keeps the ventricles from collapsing which is called slit ventricles. Slit ventricles occur due to overdrainge of CSF by external surgical shunts. They can also occur when the normal CSF pressure gradient is reversed. I will discuss shunts, siphons and slit ventricles further in future posts. In addition to maintaining the size of the ventricles turgor helps to keep the brain afloat and prevent it from sinking or making contact with the cranial vault.

Turgor has its limitations, however. Too much turgor limits the compliance of the brain. Compliance is a term used to describe the stretch phase of elasticity in the brain. Compliance allows tissue to deform without damage such as with compression and stretching. Elastance is the complete opposite of compliance. Elastance is the strength of tissues to resist deformation and  return to their original shape once the load is removed. Elastance preserves the designs and shapes of structures. On the other hand, the compliance of certain tissues in the brain, especially weak-walled veins, allows them to buffer the impact of the relatively large volume of blood and the associated increase in pressure that is pumped into the cranial vault with each contraction phase of the heart roughly seventy times per minute. The strength of the arterial waves of blood and the pressure pumped in during each heart beat needs to be decreased and modified before sending it into the delicate internal structures of the brain.

The dark grey areas on the bran scan above is CSF. As you can see, CSF fills all the spaces, cracks and caves. The brain is also contained inside the cranial vault and surrounded by CSF that maintains its position and prevents contact with the bones of the vault. Although it is highly porous, the interior and exterior surfaces of the skull are more like limestone or granite in that it has poor permeability. The non-permeable hard shell of the skull protects the brain and keeps the weather out. Although it lacks permeability, the skull is penetrated by many holes called foramen and other openings, which makes it highly porous. Nerves, blood and CSF travel through these openings. Moreover, pressure in these openings can have a profound effect on fluid mechanics in the brain.

foramen magnumWhile it is not considered to be a factor that directly affects compliance (elasticity) in the brain, the foramen magnum and spinal canal play an important role in maintaining CSF volume and pressure in the brain. As shown in the picture on the left of the skull base, the foramen magum is the large hole in the base of the skull that connects the cranial vault to the spinal canal. The arterial pulsations and pressure waves that are pumped into the brain by the heart are not only buffered but a proportionate outflow in the amount of blood and CSF is also transferred out of the cranial vault and brain through the foramen magnum and into the spinal canal.

Obstruction of venous and CSF pathways in the foramen magnum can affect intracranial pulsatility and pressure waves. In particular it can cause back pressure on the drainage system that results in increased turgor resulting in stiffness due to loss of compliance (elasticity). Obstruction to blood and CSF flow through the foramen magnum can also cause CSF inversion (reverse) flows, turblulence and water hammers in the brain. CSF inversion flows, turbulence and water hammers may play a destructive role that results in damage to periventricular structures.

The most common place for obstruction of CSF outflow to occur is in the craniocervical junction (upper cervical spine). The most common causes of obstruction in the craniocervical junction are malformations and mechanical strains such as misalignments. Obstructions due to malformations and mechanical strains indirectly but significantly affect intracranial compliance (elasticity) and the ability of the brain to absorb and control fluid mechanics caused by heart contractions.

To get a better understanding of how faulty fluid mechanics batter the brain, researchers and engineers are now plugging biphasic poroelastic properties of the brain into computational fluid dynamics and finite element analysis formulas to form computer models to predict and determine the cause of ventriculomegaly. They are also using physics formulas for computational fluid dynamics to determine flow through the different structures of the brain such as the ventricles. The different structures of the brain and the skull have complex shapes and different materials with different degrees of strength and compliance (elasticity), as well as their differing response to hydraulic pressure.

Hydraulic force is a product of pressure multiplied by the size of the area the pressure is being applied to, such as the volume of the ventricles or cisterns for example. A hydraulic pump can be used to increase force by applying pressure to a larger cylinder. Similarly, the pressure from the heart exerts more force on the larger pores and spaces of the brain compared to smaller ones. In this regard, the largest spaces in the brain are the ventricles and cisterns. The effects of hydraulic force may play a role in the ventriculomegaly seen in neurodegenerative condtions such as Alzheimer’s, Parkinson’s and multiple sclerosis. Constant strain from increased force in the ventricles and cisterns may cause a breakdown in the elastic properties of the brain so that the ventricles and surrounding structures can no longer return to their original shape, which is called plastic (permanent) deformation. Dr. Hakim also suggested, many years ago, that the greater size of the ventricles allow them to exert more force and thus maintain the ventriculomegaly with relatively lower pressure (turgor).

In addition to Hakim’s theory regarding ventriculomegaly, my theory regarding mega cisterns, which are enlarged cisterns, is that they are caused by inversion flows, turbulance and hydraulic forces that damage the brainstem and cerebellum resulting in atrophy of nearby structures. Mega Cisterns and atrophy of the brainstem are seen in mega cisterna magna, the Dandy-Walker Complex-Continuum, and a variant form of Parkinson’s disease called olivopontocerebellar atrophy, also known and Shy-Drager Syndrome or Multisystem Atrophy. Understanding these conditions will shed further light on the role of faulty fluid mechanics and hydraulics in neurodegenerative conditions of the brain. I have covered these conditions previously and will cover them more in future posts.

Hydrofracking is a term method engineer’s use to fracture rocks with water pressure. A similar situation called a water hammer can occur in the brain and damage delicate tissues. The location of the periventricular tissues predisposes them to compression, shear forces and water hammers that can cause damage. Loss of compliance in the brain magnifies the destructive forces. My next post will be on hydrofracking and brain atrophy (shrinkage).

For further information on enlargement of the ventricles and autonomic dysfunction called dysautonomia visit my website www.upright-health.com.

Posted in Alzheimer's, CSF, multiple sclerosis, Parkinson's | 4 Comments

Pulsatility, Pressure Waves and Neurodegenerative Diseases

The red colored areas in the picture on the left represent the ventricles of the brain. You can click on the image to enlarge it and get a closer view. The ventricles of the brain contain and produce cerebrospinal fluid (CSF). CSF is mostly water with some sugar and other elements mixed in. CSF leaves the ventricles and enters the subarachnoid cisterns and spaces that surround the entire brain. The subarachnoid cisterns and spaces are part of the protective membranes of the brain and spinal cord called meninges.

CSF leaves the subarachnoid space and enters the superior sagittal sinus, which is part of the venous drainage system of the brain. The dural sinuses are the large striped blue colored veins in the picture on the left. The veins of the brain also empty into the dural sinuses. They are depicted as the smaller light blue vessels on the surface of the brain. The primary drainage routes of the dural sinuses empty into the internal jugular veins and the vertebral venous plexus of the spine. The internal jugulars and vertebral veins are the large, vertical,  blue vessels beneath the skull. Increased pressure or obstruction of the venous outlets of the brain can affect CSF flow and volume. It can also effect pulsatility and pressure waves in the brain which will be explained further below.

The brain scan on the right is from a paper published in the American Journal of Roetgenology in 2002 called Lesions of the Corpus Callosum: MR Imaging and Differential Considerations in Adults and Children. by E.C. Bourekas and others. The corpus callosum is a large white matter myelinated structure that covers the top of the lateral ventricles. In this image the corpus callosum is the dark grey area above the large white space below the arrows. The large white space is the lateral ventricle which is filled with CSF, and appears white in this image. The arrows are pointing to white spots in the corpus callosum called hyperintensity signals.  They indicate demyelinating lesions in the white matter tracts of the corpus callosum.

Interestingly, the ventricles and periventricular areas (which is where the corpus callosum is located) are often involved in neurodegenerative diseases. For example, enlarged lateral ventricles have been associated with normal pressure hydrocephalus (NPH), Alzheimer’s and Parkinson’s disease. NPH is a condition that occurs in adults when the ventricles of the brain become enlarged due to an increase in CSF volume but pressure in the brain, called intracranial pressure, remains normal or just slightly elevated. Parkinson’s disease and Dandy-Walker syndrome are associated with an enlarged fourth ventricle, as well as enlargement of the subarachnoid cisterns. More recently, multiple sclerosis has been associated with an enlarged third ventricle. I cover CSF and the ventricles’ role in the conditions listed above in my book,“The Downside of Upright Posture – The Anatomical Causes of Alzheimer’s, Parkinson’s and Multiple Sclerosis.”

In any case, the enlarged ventricles are typically attributed to atrophy. The cause of the atrophy (decrease in size), however, is often unknown. In this regard, neurodegenerative conditons are also often associated with hyperintensity signals and degeneration of the delicate tissues located next to the ventricles called the periventricular area.  Among other things, the periventricular area forms an interface between the brain and ventricles similar to different soil layers called strata or the tectonic plates of the earth. Just like soil strata and tectonic plates, the lobes of the upper brain can similarly slide on the periventricular surfaces of the lower brain and cause a strain.

The periventricular interface contains small blood vessels and delicate myelin covered nerves. Scientists have suspected for decades that myelin is more sensitive to shear stresses and strains. They maintain that enlargement of the ventricles can cause nearby myelin to over-stretch and snap. They further suspect that myelin is more easily damaged by decreases in blood flow (ischemia) and that mechanical stresses and strains may damage the smaller periventricular blood vessels. This could lead to chronic ischemia and atrophy (decrease in size) of the brain. Researchers suggest that the ventricles enlarge to fill the vacated space caused by the atrophy of the surrounding tissues. Interestingly, in addition to atrophy and enlarged ventricles, hyperintensity signals are often in the periventricular areas in Alzheimer’s and multiple sclerosis as mentioned and shown in the brain scan above. Among other things, hyperintensity signals can be a sign of demyelination. They can also be a sign of ischemia. In future posts I will explain how, because of its location, the periventricular area is caught between a rock and a hard place. Consequently, the periventricular area suffers the consequences of faulty hydraulics in the brain.

Researchers are currently studying the potential role of  pulsating, strong, high pressure waves in neurodegenerative diseases as a cause of atrophy. The strong, pulsatile, high pressure waves come from the heart which pumps a relatively large volume of blood into the brain with each beat. This causes rhythmical pulsations of increased volume of blood in the brain that produces increased pressure waves that ripple through the entire brain from the point of entry to its exit routes within the cranial vault.

Under normal circumstances, arterial pulsations entering the brain are buffered in and by the subarachnoid cisterns and spaces. The subarachnoid cisterns and spaces are part of the protective membranes that surround the brain called the meninges, mentioned above. The impact of high pressure arterial pulsations from the heart are typically absorbed and reduced in the brain by the elasticity, technically called compliance, of the arteries, veins and the subarachnoid space of the brain and cervical spinal cord. The cervical spinal cord subarachnoid space communicates with the subarachnoid space in the brain.

Most of the force from arterial pulsations is normally absorbed by veins in the subarchnoid space which have weak walls that are easily compressed. The impact of arterial pulsations in CSF and the rhythmical compression of the veins help to move venous blood and CSF through their pathways and out of the cranial vault. Scientists suspect that problems can occur if high arterial pressure waves aren’t sufficiently buffered in the subarachnoid space, but instead are directed into the core of the brain and the more delicate micro-sized capillary blood vessels.

In this regard, studies have shown that excessive pulsatile stresses in the small blood vessels of the brain can change the way their endothelial cells function. Endothelial cells form the innermost lining of blood vessels. They open and close their pores according to chemical and mechanical signals and stresses. Damage to the endothelial cells can affect blood flow. Weakness and thinning of the endothelial cells for example, can make them more susceptible to internal tears and penetration from elements carried in the blood stream such as fats. Constant pounding from high pressure waves can also cause thickening and a decrease in the size of the openings in the endothelial cells and thus decrease blood flow out of the blood vessels. High internal endothelial pressure can also cause stiffness or lack of compliance in the arterial system. In contrast to internal pressure, the small blood vessels can also be effected by external pressures from parts of the brain, the skull or CSF.

Scientists and engineers are now using biphasic poroelastic properties in computational fluid dynamics and finite element analysis to model tissues and fluid mechanics in the brain. Poroelasticity is a complex subject related to geotechnical engineering regarding soils and rocks. It is is also known as the consolidation theory in soil mechanics as first described by professor of physics M.A. Biot from Columbia University. Basically, porous materials contain spaces called pores or voids and are elastic. The flow of fluids through porous materials, such as rocks, is a separate study. Engineers use complex physics formulas and computer programs for computational fluid dynamics to predict hydraulics and fluid flow through soils and rocks.

Fluids inside poroelastic materials affect the material’s structural strength and the way it responds to stresses and strains (deformation). The many different types of soils and rocks all have different types of pores that affect their structural strength and their stability under stresses and strains. In addition to overall strains, engineers use finite element analysis to break down larger macrostrains into smaller microstrains located at intersections along the overall strain.

The brain is loaded with many non-spherical, irregularly shaped pores, ventricles (caves), fissures (cracks), sulci (valleys) and other assorted spaces and shapes that make it difficult to interpret and predict tissue deformation, fluid behavior and hydraulics based on brain scans. Tissue deformation and hydraulics in the brain are important to neurosurgeons for many reasons, including shunt surgery. The use of a mechanical model for more realistic geometry of the brain was proposed decades ago by Dr. S. Hakim,  a neurosurgeon, who was one of the pioneers in NPH.

Dr. Hakim published a paper in Surgical Neurology in 1976 called, The Physics of the Cranial Cavity, Hydrocephalus, and Normal Pressure Hydrocephalus: Mechanical Interpretation and Mathematical Model. Dr. Hakim also introduced the concept of the brain being a sponge-like material (poroelastic). More recently, a paper was published by the Oxford University Computing Laboratory in 2004, “A Hydro-elastic Model of Hydrocephalus” by A. Smilie and others, which combines poroelasticity and fluid mechanics to, likewise, construct a mathematical model of the human brain and ventricles. Mathematical models provide clues as to how faulty hydraulics may play a significant role in neurodegenerative diseases.

In brief, for engineering purposes and computer modeling, the fluid mechanics in the cranial vault and and brain can be compared to hydraulic stresses in rocks and soils. My next post will be on the role of poroelasticity in brain pulsations, pressure waves and deformation, such as atrophy and enlarged ventricles. For further information regarding common signs and symptoms of neurodegenerative diseases that are most likely related to hydraulic stresses acting on the third ventricle, such as frequent urination, incontinence, cog fog, heat intolerance, etc.,  visit my website at upright-health.

Posted in Alzheimer's, CSF, ms lesions, Parkinson's | 1 Comment

Blood, CSF and Battered Bones

Fluid mechanics is the science of liquids, gases and plasmas, as well as the forces that act on them. Hydraulics is based on the science of fluid mechanics and the mechanical properties of fluids.

Hydraulic pressure is the force exerted by a fluid against a given area such as the inside surface of a container or a pipe. The force is determined by properties of the fluid and the design and dimensions of the container or pipe. In theory, if two containers are linked with a pipe and filled with fluids, force applied against a large container and transmitted via the pipe to a smaller container decreases the force in the smaller container due to the decrease in its size. If pressure is exerted against a container connected to another one of equal size the force stays the same. If the pressure is transmitted to a larger container the force goes up due to the larger size of the area that the pressure is exerted against. In medical sciences, radiologists refer to fluid mechanics and hydraulics in the brain as cranial hydrodynamics.

Cranial hydrodynamics (hydraulics) are driven by cardiorespiratory pressure fluctuations. When the heart contracts it pumps a large quantity of blood into the brain under pressure. It then relaxes, which relieves the pressure. This causes the soft tissues of the brain to rhythmically deform and reform in continuous expansion and contraction cycles. The force cranial hydrodynamics exerts on the different areas of the brain is not uniform. It varies according to the design and dimensions of the different chambers transmitting the force, as well as those that receive it. Thus, a low pressure and force from a smaller chamber can generate greater force when it acts on a larger chamber in the cranial vault.

Poroelasticity is an engineering term used to describe the interaction between rocks and fluids that fill the rock’s pores. External pressue on rocks such as from a large body of water above, pounding waves or large buildings cause rocks to compress which increases pressure on the fluids that fill their pores. Conversely, increased fluid pressure in the pores of rocks such as ice can cause rocks to expand. Over time, poroelastic mechanics can cause rocks and soils to settle, subside, crack and deform. Poroelasticity can be used to describe deformation of the bones of the cranial vault and the deformation of the brain due obstruction of cerebrospinal fluid (CSF) flow.

Caves, caverns and cavities in rocks are often formed by the force of water. In this regard, the skull is a stone structure comprised of many rocks surrounding enclosed caves, caverns, cavities and pores formed in part by cranial hydrodynamics and the force of water. The cranial vault, for example, is a large fluid filled cave. Inside the cranial vault, the tough outer coat of the brain, called dura mater divides the cranial vault into caverns called fossas. It also forms caverns called dural sinuses. The openings in the skull called fissures and foramen are cavities that penetrate the bone stones of the skull. All bones have pores but the bones that cover the cranial vault have special, extra-large pores called diploic spaces located between the inner and outer plates of the skull bones. The dipolic spaces contain valveless veins. The diploic spaces and veins insulate, cool and help to maintain the temperature of the brain.

The bones of the cranial vault are like rocks constantly battered by blood and cerebrospinal fluid (CSF). The high pressure in the arteries is strong enough that it causes deformation leaving their distinct impression on the roof of the skull. Blood pressure in the veins is much lower so they don’t cause as much deformation and imprints on the skull bones. The largest veins of the brain called the dural sinuses, such as the superior sagittal sinus, the transverse and sigmoid sinuses, however, influence the shape of the special joints of the skull called sutures. The imprint they leave however, isn’t the same as the arterial imprints. Instead they leave behind a strange looking zig zag pattern similar to surgical sutures or stitches used in sewing.

Interestingly, the inside surface of the sutures of the skull next to the sinuses shows much smaller deformation, comparatively speaking, than the outside surface. The outer surface of the sutures and skull is instead effected by the much smaller diploic veins. The deformation and impression they leave behind are large and erratic and get progressively larger toward the back and bottom of the skull. I discussed the shape of the sutures in previous posts. They are a reflection of fluid mechanics in the brain. Suffice it to say that their shapes are not like veins but instead suggest lateral strains such as from water that sloshes from side to side in bucket while being carried.

In addition to arteries and veins, cerebrospinal fluid (CSF) can also batter the bones of the skull. Left unchecked, CSF can cause the skull to enlarge in a child with hydrocephalus or Dandy-Walker syndrome. The previous post discussed Dandy-Walker Syndrome in children which is often associated with hydrocephalus and enlargement of the posterior fossa.

The picture above on the right is of a child’s skull that was effected by hydrocephalus. Notice that the bones that typically make up the base of the skull all around the area where the ear would be are broken into many smaller sections. Those small sections of bone are called wormian or sesamoid bones. They are caused by rapid expansion of the skull, which stretches the bone to its limits. Bone development can’t keep pace and imperfections develop and voids are filled with pieces of bones to patch things over. They are similar to rock fractures caused by ice expansion and other internal forces inside the pores.

CSF is produced from blood and driven by pulsations from the circulatory system and respiration. Although it is extremely low compared to blood pressure, the hydraulic force from the pulsations of cerebrospinal fluid are strong enough to erode and leave impressions in the bones that form the roof over the cranial vault. Physical anthropologists and forensic scientists call the pits in the skull caused by CSF pulsations Pacchionian or arachnoid impressions. They are caused by the arachnoid granulations. The impressions are also known as granular foveolae. If you click on the picture at the top left of the page, you can see a large Pacchionian impression above the letter “e” in the word “bone.” A much smaller round Pacchionian impression can be seen above the larger one. As an aside, this skull also shows hyperostosis, which is associated with excess growth and thicker bones. Hyperostosis is sometimes associated with an increase in intracranial pressure due to the decrease in the inside dimensions and thus capacity of the cranial vault.

The superior sagittal sinus is located at the top of the brain. Several large reservoirs of veins called venous lacunae (lakes) are located on either side of the superior sagittal sinus. Venous blood from the brain enters the venous lacunae. CSF from the subarachnoid spaces flows through the one way valves of the arachnoid granualtions and into the venous lacuna and superior sagittal sinus.  Lacuna means lake because its a large venous reservoir. This means that the pressure exerted by the smaller container of CSF against the larger venous lacuna increases the force acting on them. The force it generates is strong enough to put a dent in the roof of the skull. Blood in the venous lacuna then empties into the superior sagittal sinus and travels down through the transverse and sigmoid sinuses and into the internal jugular and the vertebral veins located in the posterior fossa.

The thought first occured to me decades ago when I first saw Pacchionian impressions and skulls with hydrocephalus, that if CSF is powerful enough batter and erode bone, then it certainly must be strong enough to batter and erode the much softer tissues of the brain. Recent evidence from studies being done in Latham, New York, by Dr. Scott Rosa using an upright phase contrast cine MRI by FONAR Corporation continue to confirm my hypothesis. The areas I have seen effected are the front of the posterior fossa called the clivus and the rear of the fossa called the supraocciput. Interestingly, among other things, radiologists look for erosion of the clinoid process of the clivus as a sign of increased intracranial pressure. Another potential sign they look for is an empty sella, which I discussed in previous posts. CSF backjets and turbulent flows can indeed erode bone. Moreover, in addition to bone, chronic CSF backjets and inversion flows can batter and erode the brain by similar hydraulic effects.

Normal pressure hydrocephalus (NPH) is a condition seen in adults and has been associated with Alzheimer’s and Parkinson’s diseases. More recently it has been implicated in multiple sclerosis. In NPH the ventricles, likewise, become enlarged but intracranial (CSF) pressure remains normal or just slightly elevated. In addition, the size of the skull is normal but the brain decreases in size. The decrease is currently blamed on atrophy. It puzzles researchers and engineers how low pressure conditions can cause the ventricles to enlarge. It is my opinion that it may be due to erosion and subsequent atrophy caused by constant battering of the brain by aberrant CSF flow. What’s more, it’s not just the pressure that does the damage in NPH. The force generated by the hydraulic pressures acting on the designs and dimensions of different parts of the brain has to be considered as well. In my next, post I will discuss how CSF can similarly batter the brain and cause it to shrink in size while pressure remains normal or just slightly elevated due to hydraulics and poroelasticity.

Posted in Alzheimer's, CSF, multiple sclerosis, Parkinson's | 3 Comments

CSF and Cerebellar Symptoms in Alzheimer’s, Parkinson’s and MS

The cerebellum is often affected in neurodegenerative diseases such as Alzheimer’s,, Parkinson’s and multiple sclerosis (MS). Cerebellar signs include: problems with posture, balance, gait (walking) and coordination. Muscle coordination problems include disturbances in movements of the eyes such as nystagmus, as well as intention tremors and over shooting movements when attempting to do specific tasks with the arms or legs. Cerebellar signs can also include problems with speech, vertigo, nausea and vomiting. In this regard the cerebellum is often affected in different neurodegenerative diseases due its location in the posterior fossa above the foramen magnum.

The brain floats inside a jacket of water. The jacket of water includes the enlarged spaces, called cisterns (wells) beneath the bottom of the brain and surrounding the brainstem and cerebellum. The cisterns are the blue spaces in the drawing above from a neurology lecture by Dr. Anne Olsen. The cisterns support the brain and protect and cushion it from the hard walls of the cranial vault.

The cisterna magna is the largest of the cisterns and is located inferior to (below the bottom of) the cerebellum. The volume of cerebrospinal fluid (CSF) in the cisterna magna and other cisterns is crititcal to the health and function of the brainstem and cerebellum. An increase or a decrease in the normal volume of CSF in the cisterns can cause problems in the brainstem and cerebellum. For example, an insufficient volume of CSF can cause the brainstem and cerebellum to sink into the foramen magnum. On the other hand, it is my opinion that a  chronic abnormal increase in CSF volume in the cisterns can lead to compression and subsequent degeneration of the brainstem and cerebellum.

Typically, hydrocephalus is associated with an increase in CSF volume in the chambers in the middle of the brain and brainstem, called ventricles, where it is produced. There is debate among experts, however, as to whether to include any abnormal increase in CSF volume inside the cranial vault, which would include those that can occur outside the ventricles in the subarachnoid spaces and cisterns located between the outer and middle layers of the protective membranes, called meninges, that surround the brain and cord. Currently, an increase in CSF volume in the cisterna magna is called a mega cisterna magna or a cystic posterior fossa. At this time, a mega cisterna magna is not considered to be a form of  hydrocephalus but it is sometimes associated with hydrocephalus and enlarged ventricles in a rare condition called Dandy-Walker syndrome.

Dandy-Walker syndrome is a congenital condition associated with a malformed and undersized cerebellum.  The MRI on the right is an example of a Dandy Walker syndrome from a paper published in 2008 in the Internet Journal of Radiology called, Imaging of Congenital Malformations of the Brain by A.B. Shinagare and N.K. Patil from the Department of Radiology in Mumbai. The white arrow points to the cerebellum. The white dart points to the cover over the cerebellum and posterior fossa, which is exceptionally steep. The black dart near the bottom of the posterior fossa points to a dark gray area beneath the cerebellum. The dark gray is CSF in the cisterna magna of the posterior fossa. The black arrow points to the rear side of the pons portion of the brainstem, which is slightly compressed.

A normal healthy cerebellum should nearly fill the posterior fossa. In this case the cerebellum is extremely small. The malformation of the cerebellum is currently believed to be do to underdevelopment (atrophy), or to total lack of development (atresia).  The increase in CSF volume in the cisterna magna is attributed to the decrease in size of the cerebellum. In other words, CSF simply moves in to fill the empy space.

Interestingly, Dandy-Walker syndrome is the complete opposite condition to a Chiari malformation. For example, Chiari malformations are often associated with an undersized posterior fossa. In Dandy-Walker, the posterior fossa is often enlarged. In Chiari malformations, a normal sized cerebellum gets pushed down into the foramen magnum. In Dandy-Walker the cerebellum is underdeveloped and small. Moreover, it often gets pushed up into the posterior fossa of the cranial vault along with the cover over the fossa, called the tentorium cerebelli. In Chiari malformations the cisterna magna is often compressed due to the descent of the cerebellum into the foramen magnum. In Dandy-Walker syndrome the cisterna magna is enlarged. Chiari malformations are also associated with an undersized foramen magnum. Dandy-Walker, on the other hand, is associated with an oversized foramen magnum. Chiari malformations also affect females about three times as often as males. On the other hand, at approximately sixty percent, males make up more than half the cases of Dandy-Walker syndrome. The one characteristic both conditions do share in common is that their cause is often unknown.

In Dandy-Walker the problem is believed to be caused by undersized or absent outlets that normally connect the fourth and lowest ventricle to the cisterns below. The fourth ventricle is located between the front of the cerebellum in the back and the pons of the brainstem in the front. It can be seen in the sketch of the cisterns at the top of the page indicated by the Roman numeral IV in the black space. The third ventricle is above it and is indicated by the Roman numeral III in the black space. The narrow black streak joing them is called the cerebral aqueduct.

The obstruction to CSF flow from the fourth ventricle to the cisterns causes the fourth ventricle to enlarge. Chronic enlargement of the fourth ventricle can compress and damage the cerebellum. In Dandy-Walker syndrome, the enlarged fourth ventricle is referred to as a cystic fourth ventricle. Because it involves the ventricles, a cystic fourth ventricle is technically a form of hydrocephalus. On the other hand, the enlarged cisterna magna seen in certain cases of Dandy-Walkers syndrome is not. Instead, the enlarged cistern is attributed to an underdevelopment resulting in an undersized cerebellum. CSF increases in volume in the cisterna magna as a result of the decrease in size of the cerebellum. Since the cisterns are outside the ventricles, technically speaking it is not hydrocephalus.

This is similar to the theory regarding the suspected cause of enlarged ventricles often seen in normal pressure hydrocephalus (NPH), which has been associated with Alzheimer’s disease, dementia  and Parkinson’s disease as well as others. In Alzheimer’s disease the enlarged ventricles are attributed to atrophy; that is, a decrease in size of the brain. In other words, as the brain shrinks in size the ventricles enlarge and CSF volume increases to compensate for the decrease in size of the brain and to fill in the space.

While some cases of Dandy-Walker are clearly associated with undersized, blocked or absent CSF pathways, many are not. The problem is further complicated because the development of the ventricles, as well as the cisterns and CSF pathways start in utero (during preganancy) and continues after birth, which is when problems start to show up. Moreover, the skull is still open at birth, which allows it to accomodate an increase in CSF volume. Consequently, unless it is associated with an oversized head due to hydrocephalus, the problem often  goes unnoticed initially . Whatever the cause, experts all agree that Dandy-Walker syndrome is associated with an imbalance between the rate of production of CSF and its absorption and removal from the brain.

Considering the above, both blood and CSF flow between the brain and cord pass through the foramen magnum and upper cervical spinal canal. Consequently, blockage of blood and CSF flow through the foramen magnum and upper cervical spinal canal can cause inversion flows, turbulance and standing waves to form in the brain, especially in the cisterna magna, which can affect the cerebellum among other things. It can also cause the posterior fossa and foramen magnum to enlarge similar to the affects of hydrocephalus on the upper portion of the cranial vault. This could explain the enlarged posterior fossa and foramen magnum in Dandy-Walker syndrome. Furthermore, it is my contention that chronic obstruction to CSF flow causes local turbulance, inversion flows and standing waves (clapotis) in the brain that can compress and erode the brain.

Other cisterns can similarly be affected in conditions that affect adults. For example, there is a variant of Parkinson’s disease called multi-system atropy (MSA) or olivopontocerebellar atrophy (OPCA) in which the cerebellum and sometimes parts of the brainstem, called the olives and pons, appear small and compressed similar to Dandy-Walker. It is my theory that many cases of Parkinson’s disease and variants of Parkinson’s are due to obstruction to CSF flow oftentimes due to Chiari malformations, which block blood between the brain and cord in the foramen magnum and upper cervical spinal canal. Moreover, obstruction to CSF flow most likely plays a role in multiple sclerosis and Alzheimer’s disease as well. The first place to feel the affect of blockage of CSF flow is the posterior fossa, which contains the brainstem and cerebellum.

In brief, hydrocephalus is associated with children. In contrast to children, adults get normal pressure hydrocephalus. Similarly, Chiari malformations and Dandy-Walker syndromes are associated with children. More recently however, it has been shown that adults can aquire Chiari 1 type malformations, and olivopontocerebellar atrophy (a variant of Parksinson’s) causes similar signs on brain scans to Dandy-Walker syndrome.  In many cases they may share a similar cause, which is blockage of CSF flow that results in an imbalance between its rate of production and removal from the brain. Among other things, an increase in CSF volume in the fourth ventricle or cisterns can affect the cerebellum.

For further information on CSF flow and volume in the cisterns, dysautonomia and heat intolerance, visit my website at www.upright-health.com.

Posted in Alzheimer's, chiari malformations, Dandy-Walker syndrome, multiple sclerosis, Parkinson's | 35 Comments