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Hydrocephalus is caused by an imbalance between how much cerebrospinal fluid is produced and how much is absorbed into the bloodstream.

Cerebrospinal fluid

Cerebrospinal fluid is produced by tissues lining the ventricles of the brain. It flows through the ventricles by way of interconnecting channels and eventually flows into spaces around the brain and spinal column. It's absorbed primarily by blood vessels in tissues near the base of the brain.

Cerebrospinal fluid plays an important role in brain function by:

  • Keeping the brain buoyant, allowing the relatively heavy brain to float within the skull
  • Cushioning the brain to prevent injury
  • Removing waste products of the brain's metabolism
  • Flowing back and forth between the brain cavity and spinal column to maintain a constant pressure within the brain — compensating for changes in blood pressure in the brain

Excess fluid

Excess cerebrospinal fluid in the ventricles occurs for one of the following reasons:
  • Obstruction. The most common problem is a partial obstruction of the normal flow of cerebrospinal fluid, either from one ventricle to another or from the ventricles to other spaces around the brain.
  • Poor absorption. Less common is a problem with the mechanisms that enable the blood vessels to absorb cerebral spinal fluid. This is often related to inflammation of brain tissues from disease or injury.
  • Overproduction. Rarely, the mechanisms for producing cerebrospinal fluid create more than normal and more quickly than it can be absorbed.
Sep. 13, 2011