Hydrocephalus is a build-up of fluid inside the skull, which causes brain swelling. Hydrocephalus means "water on the brain."

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.

The symptoms depend on the cause of the blockage, the person's age, and how much brain tissue has been damaged by the swelling.

In infants with hydrocephalus, CSF fluid builds up in the central nervous system, causing the fontanelle (soft spot) to bulge and the head to expand.

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.

See also: Normal pressure hydrocephalus (NPH)

Early symptoms in infants:

• Enlarged head (increased head circumference)
• Bulging fontanelles (soft spots of the head) with or without enlargement of the head size
• Separated sutures
• Vomiting

Symptoms of continued hydrocephalus:

• Irritability, poor temper control
• Muscle spasticity (spasm)

Symptoms that occur later in the disease:

• Decreased mental function
• Delayed development
• Slow or restricted movement
• Difficulty feeding
• Lethargy, excessive sleepiness
• Urinary incontinence (loss of control over bladder)
• Brief, shrill, high-pitched cry
• Slow growth (child 0-5 years)

Symptoms in older babies and children:

• Headache
• Vomiting
• Vision changes
• Crossed eyes
• Uncontrolled eye movements
• Loss of coordination
• Poor gait (walking pattern)
• Mental aberrations (such as confusion or psychosis)
• Changes in facial appearance and eye spacing

When a health care provider taps fingertips on the skull, there may be abnormal sounds that indicated thinning and separation of skull bones. Scalp veins may appear stretched or enlarged (dilated).

Part or the entire head may be larger than normal. Enlarge is most commonly seen in the front part of the head. Head circumference measurements, repeated over time, may show that the head is getting bigger.

The eyes may look "sunken in." The white part of the eye (the sclera) may appear above the colored part of the eye (the iris), given the eyes a "setting-sun" appearance. Reflexes may be abnormal.

The following tests may be performed:

• Transillumination of the head (shining a light against the head)
• Head CT scan (one of the best tests for identifying hydrocephalus)
• Spinal tap and examination of the CSF (rarely done)
• Skull x-rays
• Brain scan using radioisotopes
• Arteriography
• Echoencephalogram, an ultrasound of the brain