HYDROCEPHALUS

Hydrocephalus is a term derived from the Greek words "hydro" meaning water, and "cephalus" meaning head, and this condition is sometimes known as "water in the brain". People with this condition have abnormal accumulation of cerebrospinal fluid (CSF) in the ventricles, or cavities, of the brain. This may cause increased intracranial pressure inside the skull and progressive enlargement of the head, convulsion, and mental disability.

Hydrocephalus is usually due to blockage of CSF outflow in the ventricles or in the subarachnoid space over the brain. In a normal healthy person, CSF continuously circulates through the brain and its ventricles and the spinal cord and is continuously drained away into the circulatory system. In a hydrocephalic situation, the fluid accumulates in the ventricles, and the skull may become enlarged because of the great volume of fluid pressing against the brain and skull. Alternatively, the condition may result from an overproduction of the CSF fluid, from a congenital malformation blocking normal drainage of the fluid, or from complications of head injuries or infections.

Infants and young children with hydrocephalus typically have abnormally large heads, because the pressure of the fluid causes the individual skull bones — which have not knitted with each other yet — to bulge outward at their juncture points. Compression of the brain by the accumulating fluid eventually may cause convulsions and mental retardation. Hydrocephalus occurs in about one out of every 500 live births and was routinely fatal until surgical techniques for shunting the excess fluid out of the central nervous system and into the blood or abdomen were developed.

Usually, hydrocephalus need not cause any intellectual impairment if recognized and properly treated. A massive degree of hydrocephalus rarely exists in normally functioning people, though such a rarity may occur if onset is gradual rather than sudden.