Hydrocephalus

The word hydrocephalus is derived from the Greek words meaning “water” and “head,” and thus is defined as the accumulation of cerebrospinal fluid (CSF) in the ventricles of the brain, causing their enlargement and swelling. The estimated prevalence worldwide is 1 to 1.5 percent, or approximately 60 million individuals. It is one of the most common neurologic problems that affect humankind.

There are two major types of hydrocephalus: obstructive (noncommunicating) and nonobstructive (communicating). Obstructive hydrocephalus occurs when the normal circulation of CSF is blocked (obstructed), usually between the third and fourth ventricles at the aqueduct of Sylvius. Nonobstructive hydrocephalus is a result of poor absorption of CSF at the level of the arachnoid granulations; the flow of CSF in nonobstructive hydrocephalus is otherwise normal. Hydrocephalus can also be caused by excessive CSF production, such as with a choroid plexus papilloma.

An example of nonobstructive hydrocephalus is normal pressure hydrocephalus (NPH), a common neurologic problem that afflicts the elderly. Patients are usually older than 60 years and males are affected slightly more often than women. The classic clinical triad is dementia, gait disturbance, and urinary incontinence. The hydrocephalus is termed normal pressure because the opening pressure on lumbar puncture is nonelevated.

Other specific types of hydrocephalus include hydrocephalus ex vacuo (enlargement of the ventricles due to loss of cerebral tissue, that is, cortical atrophy, which can occur naturally with age), hydranencephaly (absence of a substantial amount of brain tissue), external hydrocephalus (enlarged subarachnoid spaces over the frontal lobes), arrested hydrocephalus (hydrocephalus without symptoms), and entrapped fourth ventricle (a fourth ventricle that does not communicate with the third ventricle).

Etiologies of hydrocephalus can be divided into two broad categories: congenital and acquired. Congenital causes of hydrocephalus include neural tube defects, Chiari malformations, aqueductal stenosis, aqueductal gliosis, Dandy-Walker malformations, X-linked inherited disorders, and intrauterine infection. Acquired causes of hydrocephalus include infections (i.e., meningitis, cysticercosis), hemorrhage (i.e., subarachnoid hemorrhage, intraventricular hemorrhage), masses, postoperative changes, neurosarcoidosis, and spinal tumors.

The signs and symptoms of active hydrocephalus in young children include an enlarging cranium, irritability, poor head control, nausea and vomiting, enlargement and engorgement of scalp veins, cranial nerve VI (abducens) palsy, upward gaze palsy, hyperactive reflexes, and irregular respirations. In older children and adults, other symptoms include papilledema (swelling of the optic nerves on ophthalmologic examination), headaches, and gait changes.

The treatment of hydrocephalus can be procedural, medical, or surgical. Procedural treatment of hydrocephalus is accomplished with spinal taps (lumbar puncture), which drains out CSF. Medical treatment is accomplished with diuretics, particularly acetazolamide; this, however, is only a temporary measure. The definitive treatment of hydrocephalus is surgical, of which there are four options. Choroid plexectomy is a procedure that targets the choroid plexus, which is present in the brain's ventricles and produces CSF. Another option is to open a narrowed Sylvian aqueduct. Third ventriculostomy is a surgical procedure in which holes are made in the floor of the third ventricle, allowing CSF to drain into the basal cisterns of the brain. This procedure is typically done endoscopically and recent studies have shown it to be more beneficial in younger patients. Last, the most common surgical option is shunting.

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