Alzheimer's, Parkinson's and Multiple Sclerosis
Getting to the Root Causes of Neurodegnerative Diseases
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.
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