Medical Therapy

Abandoned therapies include glycerol, isosorbide, radioactive gold, and head wrapping. Diuretics are occasionally used for neonatal hydrocephalus secondary to intraventricular hemorrhage to temporize ICP control until enough blood is reabsorbed. Acetazola-mide and furosemide are the drugs typically used, but both can cause significant electrolyte imbalance.

In neonatal IVH, spinal taps also serve as a temporizing measure to keep ICP in the "safe" range until CSF reabsorption resumes. In cases in which ventricular enlargement persists after the disappearance of blood and return of CSF protein to near normal levels, the patients must proceed to surgical therapy.

B. Surgical Therapy

The bulk of therapy for hydrocephalus is surgical. In an acute situation, CSF may be drained via a ventricular catheter to a sterile bag. Normally this is not done for longer than 2 weeks. Most hydrocephalus is treated by shunt placement. Shunts are permanently implantable devices for the diversion of CSF to one of several extracranial sites. They consist of a ventricular catheter, a valve, and tubing draining to a body cavity.

1. Temporary Diversion

Temporary diversion is sometimes sought when there is known infection in the CSF space precluding the implantation of permanent devices. This temporary diversion typically employs a catheter inserted into the ventricle that is tunneled underneath the scalp and connected to an external drainage bag. These systems are utilized for a few days until a permanent shunt can be placed if possible.

2. Routes of Diversion

The ventriculoperitoneal shunt is the most frequently employed route of diversion. Advantages include its relative simplicity and its complications are typically easier to manage than with other routes of diversion.

The ventricular catheter is inserted into the frontal horn of one of the lateral ventricles via frontal or occipital approaches. It is attached underneath the scalp to a valve, from which tubing passes subcuta-neously down to the peritoneal cavity. This operation is often performed employing only two small incisions—the first for passing the catheter into the ventricle and the second for entry into the peritoneal cavity. The tubing is passed from one incision to the other using specially designed tunneling devices.

Ventriculoatrial shunting was the preferred route for shunting before ventriculoperitoneal shunting became popular. It is still widely employed primarily in some centers or where peritoneal shunting cannot be used.

The ventricular catheter is placed in the standard way, and the distal tubing is passed into the internal jugular vein and down to the right atrium, usually through the common facial vein, which is a small tributary of the jugular vein in the neck.

Other distal sites include the pleural cavity (a common option for diversion after the peritoneal cavity), the gallbladder, and ureter. These are rarely employed because of technical difficulty, much higher complication rates, and diversion to the ureters has typically required a nephrectomy.

Torkildsen preceded extracranial CSF shunting in its development. It involves the placement of a catheter from the lateral ventricle into the cisterna magna—the large subarachnoid space adjacent to the cerebellum and brain stem. It is useful only for aqueductal stenosis, a fourth ventricular pathology. It has been replaced by endoscopic ventricular fenestration.

There are two main valve types: differential pressure valves and variable resistance constant flow vavles. Different pressure valves provide a constant resistance and permit the flow of CSF when a certain hydrostatic pressure has been exceeded. This is the common basic valve design and includes slit valves, ball-in-cone valves, and diaphragm valves. Recently, a variable pressure valve has been created that controls the pressure of CSF release.

Variable resistance constant flow valves attempt to maintain more natural constant flow rates by varying the amount of resistance to flow in response to pressure changes and, indirectly, to posture. These valves are believed to lead to overdrainage less often than do differential pressure designs.

The use of lumboperitoneal shunts fell out of favor largely because of distal obstruction and the high incidence of kyphoscoliosis. Use of these shunts involved a laminectomy, and the tubing initially used had a propensity to cause a chemical arachnoiditis.

This technique has been repopularized with the introduction of less irritating Silastic tubing and due to the ability to place the tubing percutaneously, with specially designed needles, into the subarachnoid space without a laminectomy.

3. Endoscopic Therapy

The most common endoscopic technique in use today is the third ventriculostomy method. This is used when CSF absorption is believed to be normal but there is an obstruction to its egress from the third ventricle. In this procedure, an endoscope is introduced into the third ventricle (typically via a frontal approach) and a small hole is made in the floor of the third ventricle to permit the flow of CSF from this cavity into the subarachnoid space, thereby bypassing any mechanical obstruction in the ventricular system. The major indication for this procedure is aqueductal stenosis. Most surgeons, however, are not specifically trained in performing this procedure, and its widespread application is further limited by patient selection.

Newer endoscopic techniques include aqueducto-plasty, which involves the endoscopic repair of short-segment strictures in the aqueduct, but experience is still limited with this procedure.

4. Lesion Removal

Occasionally, there are clinical situations in which a single lesion can be removed to cure, or at least improve, hydrocephalus. Certain tumors are amenable to removal. A choroid plexus papilloma, which overproduces CSF, can be resected, thereby obviating the need for a shunt. Another typical example is a colloid cyst, which commonly occurs around the foramen of Monro, obstructing CSF flow. Resection can lead to complete resolution of the obstructive hydrocephalus.

5. Choroid Plexectomy (Obsolete)

This procedure was performed as an open operation and involved the cauterization of choroid plexus. This carried a very high mortality early on, and it fell into disfavor. Later attempts were made to perform this endoscopically, and mortality rates decreased significantly, but it has not regained widespread use because of the relative safety and ease of other operations.

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