What Causes Hydrocephalus?

Hydrocephalus is the abnormal and dangerous buildup of cerebrospinal fluid (CSF) within the brain. Commonly referred to as “water on the brain,” the term hydrocephalus is derived from a combination of two Greek words: hydro (water) and cephalus (head).

Hydrocephalus affects more than a million people in the United States, ranging from infants and children to middle-aged and older adults. While anyone can develop this complex medical condition, most cases are concentrated in two groups: newborns and adults older than age 60.

In this blog, fellowship-trained neurosurgeon Jose Valerio, MD, explains what hydrocephalus does to the brain, explores its primary causes, and touches on the treatment options available at his practice, which has offices in South Miami, Hialeah, and Weston, Florida.

What is hydrocephalus?

Cerebrospinal fluid is the clear, watery fluid that washes over your brain and spine. It exists to protect and cushion the brain, deliver vital nutrients to brain tissues, and remove harmful waste products.

The average brain produces about 1 pint of CSF each day, or just enough to meet its daily needs. Produced mostly by the highly vascularized choroid plexus tissues within the brain’s deep ventricles, this vital protective liquid flows through the ventricles and bathes the brain and spinal cord before it’s absorbed into the bloodstream.

The production, use, and absorption of CSF is a tightly regulated process. When that process is disrupted, it can create a harmful imbalance between how much CSF is produced and how much is reabsorbed into the bloodstream.

Hydrocephalus occurs when the brain produces more CSF than it needs, when the flow of fresh CSF is blocked, or when used CSF isn’t absorbed into the bloodstream efficiently. In any of these situations, CSF builds up inside the brain’s deep ventricles and makes them swell, exerting pressure on the brain.

Why does hydrocephalus occur?

The internal pressure caused by too much CSF can damage brain tissues and impair brain function. Left untreated, it’s often fatal. But why does this dangerous fluid imbalance occur in the first place?

There are three main types of hydrocephalus, each of which has various potential underlying causes:

Congenital hydrocephalus

Congenital hydrocephalus occurs when a baby is born with a CSF imbalance. In many cases, it’s thought to be a result of the complex interaction between various genetic and environmental factors during fetal development.

It may be caused by a brain or spine malformation (central nervous system birth defect) that restricts the flow of CSF within the brain. It may also be caused by an infection in the uterus, such as rubella or syphilis, that inflames fetal brain tissues. Sometimes, it’s the product of a congenital health condition, such as:

Spina bifida
Aqueductal stenosis
Arachnoid cysts

Hydrocephalus can be a complication of premature birth, too. Often, the cause of congenital hydrocephalus is unknown.

Acquired hydrocephalus

Hydrocephalus that develops any time after birth — and isn’t caused by a health condition that existed at birth — is called acquired hydrocephalus. This form of hydrocephalus affects people of all ages and usually develops following an illness or injury of the central nervous system.

Common causes of acquired hydrocephalus include:

Traumatic brain injuries (TBIs), such as a concussion
Lesions or tumors of the brain or spinal cord
Central nervous system infections, such as meningitis
Bleeding within the brain from a stroke or injury

As with congenital hydrocephalus, it’s not always possible to determine the underlying cause of acquired hydrocephalus.

Normal pressure hydrocephalus

Normal pressure hydrocephalus (NPH) most commonly affects adults aged 60 and older. This type of hydrocephalus occurs when CSF accumulates and causes brain ventricles to widen but does not cause a significant pressure increase within the brain.

Like acquired hydrocephalus, NPH can develop following a brain injury, bleeding within the brain, or a central nervous system infection. In many cases, the underlying cause of NPH isn’t clear.

Experts believe that, in some cases, NPH may be related to chronic health conditions that affect the circulatory system and normal blood flow, such as heart disease, atherosclerosis, peripheral artery disease (PAD), or diabetes.

How is hydrocephalus treated?

Hydrocephalus may be a life-threatening condition that can damage brain tissue and impair brain function, but fortunately, it’s also highly treatable.

Dr. Valerio uses two basic approaches to restore normal levels of CSF: He may treat the condition directly by removing what’s causing the CSF obstruction, or he may treat it indirectly by diverting the excess fluid.

Most cases of hydrocephalus are treated with shunt surgery, an indirect approach that uses an implanted device to divert excess CSF away from the brain to another area of the body where it can be absorbed. Once it’s inserted, a shunt system typically remains in place for life.

If you have questions about hydrocephalus, we have answers. To learn more, book an appointment over the phone with the practice of Jose Valerio, MD, today.