Definition of Hydrocephalus:

Hydrocephalus is a build up of fluid inside the skull, leading to brain swelling. Hydrocephalus means "water on the brain."

Causes, incidence, and risk factors:

Hydrocephalus is due to a problem with the flow of cerebrospinal fluid (CSF), the liquid that surrounds the brain and spinal cord.

CSF moves through pathways of the brain called ventricles. It also flows around the outside of the brain and through the spinal canal. Higher-than-normal amounts of CSF can occur in the brain if the flow or absorption of CSF is blocked, or if too much CSF is produced. The build up of fluid puts pressure on the brain, pushing the brain up against the skull and damaging or destroying brain tissues.

Myelomeningocele, a disorder involving incomplete closure of the spinal column, is strongly associated with hydrocephalus.

In young children, hydrocephalus may also be associated with the following conditions:

• Infections caught before birth
• Infections that affect the central nervous system (such as meningitis or encephalitis )
• Injury before, during, or after childbirth, including subarachnoid hemorrhage
• Congenital defects
• Tumors of the central nervous system

In older children, risks for hydrocephalus include:

• History of congenital or developmental defects
• Lesions or tumors of the brain or spinal cord
• Central nervous system infections
• Bleeding anywhere in the brain
• Injury

Hydrocephalus most often occurs in children, but may also occur in adults and the elderly.