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How is hydrocephalus treated?
CSF Shunting
There are a number of accepted treatments available for hydrocephalus,
most of which involve the surgical implantation of a shunt (a device
that diverts CSF from one part of the body to another) in either
the brain or the lumbar region of the spine. There are three main
types of shunts popularly used in this treatment.
A Ventriculoperitoneal Shunt (V/P) diverts the CSF from the ventricles
in the brain to the peritoneal cavity in the abdomen where the
fluid is reabsorbed into the bloodstream. The one-way valve is
placed next to the ventricle in the brain and the proximal catheter
is placed in the ventricle while the distal catheter runs from
the valve down to the peritoneal cavity. A catheter is an extremely
narrow piece of tubing used for drainage purposes. "Proximal" refers
to the catheter placed in the area to be drained, while "distal" refers
to the catheter placed in the area accepting the CSF to be absorbed.
A Ventriculoatrial Shunt (V/A) diverts CSF from the ventricles
of the brain into the right atrium of the heart. Again, the valve
rests next to the ventricle and one catheter is placed within
the ventricle. The other catheter is placed into a vein in
the neck
and then carefully advanced into the right atrium of the heart,
where the CSF is reabsorbed into the bloodstream.
A Lumboperitoneal Shunt (L/P) is popularly used when the ventricles
of the brain are too small to allow the placement of a V/P
or V/A shunt. One catheter is placed in the low back (lumbar)
area
of
the spine while the other end rests in the peritoneal cavity.
As with V/P shunts, the shunted CSF is then absorbed into the
bloodstream.
There are instances, usually as a result of head trauma, when
excess CSF needs to be drained quickly in order to alleviate
pressure
upon the brain. This is accomplished via External
CSF Drainage.
In cases such as this, CSF is drained from either the ventricles
of the brain or the lumbar region of the spine into an external
drainage and monitoring system. This is a short-term treatment
only.
Endoscopic Third Ventriculostomy
A Third Ventriculostomy is a treatment for hydrocephalus
that focuses on relieving the pressure from the buildup
of cerebrospinal fluid
(CSF) in the third ventricle. This is done via an "intracranial
CSF diversion": a tiny perforation in the wall of the third
ventricle which allows excess CSF to drain into the interpenduncular
cistern, a normal CSF space.
The procedure for a Third Ventriculostomy is relatively
simple. The surgeon makes an incision just behind the
hairline and inserts
a catheter. An endoscope is fed through the catheter and navigated
through the ventricular area of the brain to the third ventricle.
A small opening is then cut in the floor of the third ventricle
to allow for drainage. The surgeon then retracts the endoscope
and the catheter and the wound is closed. MRI scans are then
done intermittently to insure that the drainage hole
stays open.
ICP Drainage and Monitoring
Intracranial contents normally fill the skull with brain tissue,
blood, and cerebrospinal fluid (CSF). Ordinarily, the intracranial
cavity pressure-column relationship is in dynamic equilibrium.
This relationship is critical and sensitive.
Intracranial pressure (ICP) is not constant, but varies in
response to changes in vascular hemodynamics, coughing, straining,
body
position, and for many other reasons. Intracranial pressure
typically ranges from 0 to 15 mm Hg (torr). Pressures above
15 torr are
considered elevated.
The relationship between the skull and its contents determines
ICP. In pathologic conditions the skull's contents may increase
in volume. Nothing can be added to the unyielding, bony box
of the adult skull, without displacing the skull's contents
or components.
If there is an increase in the volume of one component, a reciprocal
decrease in the volume of another component occurs. This is
called a compensatory change.
Compensatory changes for increased volume within the intracranial
cavity include: CSF displaced downward into the spinal subarachnoid
space; increased absorption of CSF; and reduction in cerebral
blood volume.
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