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Hydrocephalus

Two Types Of Hydrocephalus

The two types of hydrocephalus are called communicating and noncommunicating. Communicating hydro-cephalus is caused by overproduction of fluid by the choroid plexus. The fluid, which overwhelms the absorption capacity of the arachnoid, collects inside the ventricles as well as outside the brain. This is the most common form of hydrocephalus occurring in adults and is the result of injury or infection such as encephalitis. At the onset of the condition the patient will become clumsy in walking and appear tired. Other signs will develop indicating a brain injury. To diagnose communicating hydrocephalus the physician will review the patient's recent history to determine whether an infection or head injury has occurred. In addition, such diagnostic measures as a magnetic resonance image (MRI) of the skull can reveal the presence of excess fluid. This condition is readily treatable.

Noncommunicating hydrocephalus is the most common form of the condition in childhood. Usually it will be diagnosed immediately after birth, when signs such as a swollen cranium are seen. Here the problem lies in a narrowing of a drainage aqueduct which inhibits passage of the CSF out of the cranium. The ventricles enlarge greatly and the fluid pressure begins to push the brain against the skull. In this case a drain can be implanted in the skull to drain the fluid into a vein to relieve the pressure.

This form of hydrocephalus also is associated with a congenital condition called meningomyelocele. A newborn with this condition is born with the spinal cord and its superficial coverings exposed. The spinal canal, the opening through which the spinal cord passes, has not fused, so the cord can protrude through the open side. Almost always, the surgical repair of the meningomyelocele will result in hydrocephalus, which will in turn require surgical correction.

This form of hydrocephalus also can occur in an adult and generally is the result of the formation of a tumor that blocks the drainage area.

All forms of hydrocephalus can be treated surgically, so it is important that diagnosis be made as soon as possible after the condition develops. With excessive fluid pressure inside the skull brain damage can occur, leading to various forms of disability. That can be avoided if treatment is timely.

See also Birth defects; Edema.


Resources

Books

Ziegleman, David. The Pocket Pediatrician. New York: Doubleday, 1995.

Larry Blaser

KEY TERMS

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Congenital

—A condition or disability present at birth.

Hydro

—Reference to water.

Lumbar

—Reference to the lower back; the vertebrae below the ribs or thorax.

Meninges

—Collectively, the three membranes that cover the brain and line the skull; the pia mater, arachnoid, and dura mater.

Tumor

—An uncontrolled growth of tissue, either benign (noncancerous) or malignant (cancerous).

Ventricle

—An opening in the brain that forms a reservoir for the cerebrospinal fluid.

Additional topics

Science EncyclopediaScience & Philosophy: Hydrazones to IncompatibilityHydrocephalus - Two types of hydrocephalus