by Tarek Musslimani

Created on: November 02, 2009   Last Updated: January 19, 2010

Hydrocephalus is a disorder of the cerebrospinal fluid. It is defined as an abnormal dilatation of the ventricles of the brain due to either one of two mechanisms that can contribute to the condition. These two mechanisms will be explained later.

The brain has four chambers which are called medically ventricles. These chambers communicate with each other through narrow canals which their obstruction can lead to hydrocephalus and intracranial pressure.

The ventricles of the brain are four in number and are divided to two lateral ventricles and one that is called the third ventricle which communicate with the lateral ventricles and a fourth ventricle which communicates with the third ventricle through a canal that is called the cerebral aqueduct.

The cerebrospinal fluid prvides a protection of the brain against shock or any other trauma to the brain that can happen as a result of an accident. In addition the cerebrospinal fluid contains nutrients and proteins such as immunoglobulins.

Hydrocephalus is divided into two types. These types are called communicating and non-communicating hydrocephalus. Communicating hydrocephalus means that the ventricles dilatation is due to oversecretion of the cerebrospinal fluid by the choroid plexus or due to malabsorption of the cerebrospinal fluid into the brain sinuses.

Non-communicating hydrocephalus means that the dilatation of the ventricles is due to a blockage in the flow of the cerebrospinal fluid between the ventricles or due to copression of the ventricles by a tumour such as medulloblastoma of the cerebellum.

It can also be caused due to an ependymoma of the ventricles or due to the blockage of the canals between the ventricles such as a blockage to the cerebral aqueduct which communicates the third with the fourth ventricle.

Due to its proximity to the fourth ventricle a tumor of the cerebellum can compress the ventricular system leading to hydrocephalus.

The choroid plexus in the ventricles is the site of formation of the cerebrospinal fluid. Therefore any damage to the choroid plexus whether mechanical or chemical can lead to problems in secreting the cerebrospinal fluid manifested as oversecretion. Thus leading to an imbalance between secretion and absorption of the cerebrospinal fluid. Thus leading to increased pressure of the cerebrospinal fluid inside the ventrcular system and hydrocephalus in turn.

Any obstruction to the reabsorption process of the cerebrospinal fluid into the brain sinuses can lead to

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