Hydrocephalus

Hydrocephalus, also known in the past as “water on the brain”, is a relatively common pediatric neurosurgical problem. There are a number of causes and types of hydrocephalus that may be seen. The term hydrocephalus refers to an excess of spinal fluid within the head. Spinal fluid is constantly being generated and absorbed within the head. Since the entire amount of spinal fluid in a given patient is replaced anywhere from three times per day (adult) to five times per day (infant) it doesn’t take much to cause a build-up of fluid. Unfortunately, even when the pressure in the head increases, the amount of fluid being made remains constant. This results in continued increase in intracranial pressure or in infants, excessive increase in the size of the head.

Causes of Hydrocephalus

There are a number of causes for hydrocephalus. These include blockage of spinal fluid outflow (obstructive or non-communicating hydrocephalus), impairment of spinal fluid absorption (communicating hydrocephalus) and rarely, excessive spinal fluid production (associated with a particular tumor called a choroid plexus papilloma). The most common reasons for developing obstructive hydrocephalus are aqueductal stenosis (congenital obstruction of part of the spinal fluid pathway within the brain) and various tumors. Communicating hydrocephalus is commonly seen after brain hemorrhage or infection (meningitis). Other congenital causes of hydrocephalus include Chiari malformation (usually type II in infants) and the Dandy-Walker syndrome.

Hydrocephalus Symptoms

The symptoms of developing hydrocephalus depend on the age of the patient. In infants, excessive enlargement of the head is commonly seen. This is due to the softness of the skull bones in infants and the fact that the bones have not yet fused together. The soft spot at the front of the skull will enlarge and possibly bulge outward. The child may be irritable. Vomiting is common. There may be an inability to look up (“setting sun sign”). Older children or adults will present in a different manner from infants. This difference is related to the fact that the skull is solid and the bones are strongly knit together. Increase in spinal fluid in this setting will result in increased intracranial pressure. Headaches, nausea and vomiting are common. Difficulties with vision such as visual loss, double vision and trouble looking up may be seen. As the pressure increases, drowsiness may occur and may progress to coma.

Hydrocephalus Diagnosis

As always, a careful history and physical examination are the first steps in diagnosis. In a child’s first year, the diagnosis can often be made with an ultrasound of the brain. After the skull fuses CT scanning or MRI scanning should be performed. MRI scanning is better at demonstrating small tumors and aqueductal stenosis.

Hydrocephalus Treatment

The specific treatment of hydrocephalus depends on the type and cause. Rarely is there an option other than surgery. In cases of hemorrhage in premature infants, a course of daily spinal taps may lead to resolution. Most cases of communicating hydrocephalus are treated best by placement of a shunt catheter to drain the spinal fluid away from the brain. A shunt is a small plastic tube, less than an eighth of an inch thick, that allows for fluid to flow through it in one direction. The most common type of shunt is the ventriculo-peritoneal shunt. This shunt has a one-way valve, which allows spinal fluid to drain from the ventricles to the abdominal cavity where it is then absorbed. It is also possible to drain into the blood stream using a ventriculo-atrial shunt. This is much less commonly used. Hydrocephalus related to the presence of a tumor may resolve after the tumor is removed. It is not uncommon, however, for a shunt to be needed even after tumor removal. Recently, the treatment from aqueductal stenosis has been changing from shunting to a procedure called a third ventriculostomy. In this procedure, which is facilitated by image guidance technology, an endoscope is used to open a passage from the blocked ventricles into the spinal fluid space beyond the ventricular system. This allows the obstruction to be bypassed without the need for a shunt. This procedure is fairly specialized and is usually performed by a pediatric neurosurgeon.