Hydrocephalus is a build up of fluid inside the skull, leading to 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.

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.

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. Early symptoms may also include:

• Separated sutures
• Vomiting

Symptoms of continued hydrocephalus may include:

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

Symptoms that occur later in the disease may include:

• Brief, shrill, high-pitched cry
• Decreased mental function
• Delayed development
• Difficulty feeding
• Excessive sleepiness
• Loss of bladder control (urinary incontinence)
• Slow growth (child 0-5 years)
• Slow or restricted movement

Symptoms in older babies and children may include:

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

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.

Part or the entire head may be larger than normal. Enlargement 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 may appear above the colored part of the eye, given the eyes a "setting-sun" appearance. Reflexes may be abnormal.

A head CT scan is one of the best tests for identifying hydrocephalus. Other tests that may be done include:

• Arteriography
• Brain scan using radioisotopes
• Cranial ultrasound (an ultrasound of the brain)
• Lumbar puncture and examination of the cerebrospinal fluid (rarely done)
• Skull x-rays
• Transillumination of the head (shining a light against the head)

This disease may also alter the results of a RHISA scan.