Hydrocephalus

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What is Hydrocephalus?

Hydrocephalus is an accumulation of cerebrospinal fluid (CSF) in the cavities (ventricles) of the brain. You’ve probably heard the term “water on the brain”. CSF is a water-like fluid that is constantly being produced and reabsorbed as it circulates through the ventricles to cushion the brain and deliver nutrients. When more fluid is produced than reabsorbed or the flow of CSF is blocked, excess “water on the brain” creates pressure within the skull, which can damage brain tissue if not treated. 

What causes hydrocephalus?

Hydrocephalus happens when the brain is producing more fluid than it can absorb or a blockage in one of the brain cavities is obstructing the flow of fluid. Hydrocephalus can be congenital, meaning a person is born with the condition, or it can be acquired, meaning it can develop due to injury or disease. 

Congenital hydrocephalus occurs due to a brain malformation or birth defect that occurs during fetal development. This can include:

• Brain and spinal cord (neural tube) malformations like spina bifida, Dandy-Walker malformation, or Chiari Malformation.
• Genetic factors and abnormalities may predispose children to developing hydrocephalus.
• Aqueductal stenosis, which is a narrowing of the passage that connects the third and fourth ventricles of the brain and can prevent normal CSF flow.
• Complications of premature birth.

Acquired hydrocephalus occurs after birth in children and adults and may be caused by a disease or injury that impacts normal absorption of CSF. These can include:

• Head injury or trauma that causes damage to brain tissue.
• Tumors can block the flow of CSF.
• Intraventricular hemorrhage can obstruct the normal flow and reabsorption of cerebrospinal fluid.
• Infections of the brain or spinal cord such as meningitis can cause inflammation and scarring that can block the flow of CSF.

What are symptoms of hydrocephalus?

Symptoms of hydrocephalus can vary by age and cause. Babies born with hydrocephalus typically have distinct features that include a larger than usual head or rapid head growth and a bulging or tense soft spot on the top of the head.  

Other signs of the condition may include: 

• Fixed downward gaze
• Vomiting
• Sleepiness
• Problems feeding
• Seizures

Older children and adults may experience:

• Headache
• Neck pain
• Blurred vision
• Nausea and vomiting
• Sleepiness or difficulty waking
• Slow developmental progress and delayed walking or talking
• Loss of coordination and balance or trouble walking
• Bladder control problems
• Mental confusion or memory problems

The increased pressure created by the buildup of CSF can impact normal brain function, manifesting in symptoms, like mental impairment or loss of coordination and balance, that may mimic other neurological conditions. 

How is hydrocephalus diagnosed?

Subspecialists at New Jersey Brain and Spine will first conduct a physical and neurological evaluation. Brain imaging and other advanced testing techniques can then illustrate enlarged ventricles as a result of a defect in the circulation or reabsorption of CSF (Figure 1) or  tumors, blood, inflammation and congenital defects (Figure 2) that may obstruct ventricular flow.

Figure 1
Left axial CT image shows large lateral and third ventricles when compared to normal ventricles seen on axial CT on the right.

Figure 2
Sagittal MR image with ventricular system annotated indicating position of the lateral, third and forth ventricles. The ventricular system and cerebral aqueduct show hydrocephalic changes resulting from a congenital web-like obstruction at the upper fourth ventricle (red circle).

Brain imaging and tests that can help accurately diagnose hydrocephalus include:

• Ultrasound is placed over the soft spot in a baby and can indicate pockets of fluid that are larger than normal in the developing brain.
• Magnetic resonance imaging (MRI) can clearly illustrate enlarged fluid-filled ventricles, CSF flow, and potentially the tumor or structural issue that is causing the excess fluid.
• Computed tomography (CT) is less detailed than MRI, but can detect enlarged ventricles 
• Spinal tap or lumbar puncture is used to measure the pressure of CSF or observe response to its removal. This can help rule out other conditions as well as point toward the diagnosis of hydrocephalus. 
• Intracranial pressure monitoring is used to measure the pressure inside the skull, which can help to diagnose hydrocephalus and inform treatment options.

How is hydrocephalus treated?

The most common treatment for hydrocephalus is the placement of a ventriculoperitoneal (VP) shunt (a tube), which diverts excess fluid to another part of the body to be reabsorbed. The surgeon inserts a tube into the overfilled cavity and runs another tube under the skin to the abdomen. When fluid pressure builds up on the brain, a valve system allows excess fluid to drain into the abdomen where it is reabsorbed. 

An external ventricular drain (EVD) is a method to temporarily divert fluid in cases where hydrocephalus develops suddenly and pressure needs to be reduced or when the hydrocephalus is expected to resolve. A thin tube inserted into the ventricle drains excess fluid directly into a pouch to relieve pressure on the brain.

A third method to relieve pressure when the cause is due to an obstruction to the flow of fluid is called endoscopic third ventriculostomy (ETV). This involves creating a small hole in the ventricular system to allow another path for the excess fluid to drain.   

What is the prognosis for people with hydrocephalus?

Hydrocephalus is a serious but treatable condition. Early diagnosis and proper treatment by interdisciplinary subspecialty teams like those at NJBS can prevent permanent damage and greatly improve outcomes.