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What causes hydrocephalus?
There are two main types of hydrocephalus: congenital or acquired.
The former means that the problem existed at birth, although
it may not noticeably manifest itself until later in life, perhaps
even adulthood. The latter means that the root cause of the hydrocephalus,
whether it is head trauma, tumor or infection, occurred after
birth.
Aqueductal Obstruction, or Stenosis, is the most common cause
of congenital hydrocephalus. The cerebral aqueduct, which conducts
CSF from the third to the fourth ventricle, is blocked due to
defect,
inflammation, tumor or hemorrhage. This forces CSF fluid to back
up, thereby causing hydrocephalus.
Neural Tube Defects occur when the surrounding and supporting
structure of the spinal cord, not the spinal cord itself,
is defective or
not fully developed. This malformation can create a blockage
in the opening at the base of the skull, which in turn retards
the
flow of CSF from the fourth ventricle.
Intraventricular Hemorrhage occurs most frequently in premature
babies whose blood vessels in the brain have not been able
to fully develop. Because of this weakness, the vessels
can burst,
thereby
allowing the blood to block or scar the ventricles of the
CSF pathways.
Meningitis, whether viral or bacterial in origin, causes
inflammation of the membranes surrounding the brain and
spinal cord. Scarring
of these membranes may restrict the flow of CSF and lead
to the onset of hydrocephalus.
In cases where Head Trauma occurs, blood from ruptured
vessels may lead to inflammation and scarring of the
brain membranes,
or can even block the absorption of CSF into tissue.
If these CSF
flow restrictions occur, hydrocephalus develops.
Tumors may grow in the brain and compress areas of the
ventricular system, thereby restricting the flow of
CSF and leading to
the onset of hydrocephalus.
Arachnoid Cysts, or cysts made up of CSF-filled arachnoid
membrane, may block the CSF pathways and bring on
hydrocephalus. This
condition is congenital and may occur anywhere in
the brain.
In instances of Dandy-Walker Syndrome, a congenital
defect, the fourth ventricle is enlarged and
its outlets become
obstructed. Because the flow of CSF throughout
the brain is obstructed,
hydrocephalus
develops. Normal Pressure Hydrocephalus (NPH), a form of
hydrocephalus that typically affects the elderly.
NPH is usually
characterized by
complaints of gait disturbance (difficulty walking),
mild dementia, and urinary incontinence.
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