Hydrocephalus

Hydrocephalus is a condition where fluid builds up inside the brain, creating harmful pressure that can damage brain tissue and affect how the brain works.

Table of contents

• What is hydrocephalus?
• Affected anatomy
• Types of hydrocephalus
• Causes
• Symptoms
• Diagnosis
• Treatment
• Who can be affected

What is hydrocephalus?

Hydrocephalus is the buildup of fluid in cavities called ventricles deep within the brain. The word hydrocephalus comes from the Greek words meaning “water” and “head.” The “water” is actually cerebrospinal fluid (CSF), which is a clear, colorless liquid that surrounds and protects the brain and spinal cord.^[1][2]

Normally, your body produces just the right amount of CSF each day. This fluid flows through the ventricles, bathes the brain and spinal cord, and then is reabsorbed into the bloodstream. CSF serves several important purposes: it acts as a cushion to protect the brain and spine from injury, delivers nutrients to the brain, removes waste products, and helps regulate pressure changes in the head.^[3][8]

When the normal flow or absorption of CSF is blocked, or when too much fluid is produced, CSF can build up. As it accumulates, the ventricles enlarge and put pressure on the brain tissues. This excess pressure can damage the brain and cause a range of problems related to brain function.^[1][2]

Affected anatomy

• Brain ventricles
• Brain
• Spinal cord

Types of hydrocephalus

Hydrocephalus can be classified in several different ways based on when it develops and what causes the fluid buildup.^[3][4]

Congenital hydrocephalus is present at birth. It develops during pregnancy due to a combination of genetic and environmental factors affecting the baby’s development. Common causes include birth defects affecting the brain and spinal cord, such as spina bifida.^[3]

Acquired hydrocephalus develops at birth or later in life. It is typically caused by injury or disease, such as head trauma, brain bleeding, brain tumors, or infections like meningitis.^[3][4]

Communicating hydrocephalus occurs when the flow of CSF is blocked after it leaves the ventricles. In this type, CSF can still flow between the ventricles, which remain open. The problem is usually that the fluid cannot be absorbed properly into the bloodstream. This can result from thickening of membranes at the base of the brain or from previous bleeding or infection.^[3][4]

Non-communicating hydrocephalus, also known as obstructive hydrocephalus, happens when the flow of CSF is blocked along one or more of the narrow passages connecting the ventricles. This blockage prevents fluid from moving through its normal pathways.^[3][4]

Normal pressure hydrocephalus (NPH) is a type of communicating hydrocephalus that most commonly affects older adults. In NPH, CSF buildup causes the ventricles to enlarge, but there is little or no increase in pressure inside the head. The buildup happens slowly over time, and symptoms develop gradually. NPH causes particular problems with walking, bladder control, and thinking or memory.^[2][3]

Hydrocephalus ex-vacuo results from brain damage caused by head injury or stroke. In these cases, brain tissue around the ventricles shrinks, and CSF builds up to fill the extra space. The ventricles are enlarged, but pressure inside the head usually remains normal.^[3]

Causes

Hydrocephalus can develop for many different reasons. The fluid buildup may occur when something blocks the flow of CSF through its normal pathways, when CSF is not absorbed properly into the bloodstream, or rarely, when too much CSF is produced.^[2][4]

In babies born with hydrocephalus, the condition often develops due to brain and spinal cord birth defects such as spina bifida, or genetic factors affecting development before birth.^[3]

Hydrocephalus that develops later in life can be caused by brain tumors, which are among the most frequent causes. Tumors can obstruct CSF pathways at any point. Head injuries and traumatic brain injury are significant contributors to hydrocephalus in adults.^[4][6]

Bleeding in the brain can lead to hydrocephalus. Subarachnoid hemorrhage, which is bleeding into the spaces around the brain, accounts for about one-third of cases of communicating hydrocephalus by blocking CSF absorption.^[4]

Infections of the brain and its coverings, especially bacterial meningitis, can be complicated by hydrocephalus. The infection can cause inflammation and scarring that interferes with CSF flow and absorption.^[4]

In rare cases, tumors of the choroid plexus (the tissue that produces CSF) can cause overproduction of fluid, leading to hydrocephalus.^[4]

Symptoms

The symptoms of hydrocephalus vary greatly depending on the person’s age and how quickly the condition develops.^[1][2]

Symptoms in infants

In babies, hydrocephalus may cause changes in the head. The head may be unusually large or grow rapidly. The soft spot on top of the baby’s head (called the fontanelle) may bulge or feel tense. The veins on the scalp may become more visible.^[1][8]

Physical symptoms in infants include vomiting, excessive sleepiness or sluggishness, irritability, and poor feeding. The baby’s eyes may be fixed in a downward position, sometimes called “sunsetting of the eyes,” or may not be able to turn outward normally. Seizures can occur. The baby may stop making progress in development, such as delays in walking or talking.^[1][2]

Symptoms in older children

In toddlers and older children, headaches are a common symptom. The child may experience blurred or double vision, and unusual eye movements. There may be enlargement of the head in toddlers whose skull bones have not yet fully joined together.^[1]

Other physical symptoms include sleepiness or sluggishness, nausea or vomiting, trouble with balance and coordination, and poor appetite. Children may lose bladder control or need to urinate frequently.^[1]

Changes in behavior and thinking abilities can occur. The child may become irritable or show personality changes. School performance may decline.^[1]

Symptoms in adults

Adults with hydrocephalus commonly experience headaches, blurred or double vision, and problems with eye movements. Nausea or vomiting, problems with balance and walking, poor coordination, and general slowing of movements are typical physical symptoms.^[2][8]

Adults may have sleepiness or difficulty waking up, loss of bladder control or frequent urination, and irritability. They may experience changes in personality, memory loss, problems with thinking and reasoning, or in severe cases, dementia. Walking difficulties are often described as feeling like the feet are “stuck” to the floor.^[2]

In normal pressure hydrocephalus specifically, the three most common symptoms are difficulty walking, problems controlling the bladder, and difficulties with thinking and memory.^[2]

Diagnosis

Diagnosing hydrocephalus is usually based on a combination of the person’s symptoms, a general physical examination, a neurological examination, and brain imaging tests.^[9]

During a neurological exam, a healthcare professional asks questions and conducts simple tests appropriate for the person’s age. These tests help assess muscle condition, movement, general well-being, and how well the senses are functioning.^[9]

Brain imaging tests are essential for confirming the diagnosis and identifying possible causes. Several types of imaging may be used.^[9]

Ultrasound is often the first test used for infants because it is simple, safe, and does not use radiation. The ultrasound device is placed over the soft spot on top of the baby’s head. Ultrasound can also detect hydrocephalus before birth during routine pregnancy checkups.^[9]

MRI (magnetic resonance imaging) uses radio waves and a magnetic field to create detailed pictures of the brain. This test is painless but noisy and requires lying still. MRI scans can show enlarged ventricles caused by excess fluid and can help identify the underlying causes of hydrocephalus. Sometimes children need mild sedation to help them stay calm and still during the scan.^[9]

CT scan (computed tomography) is a specialized X-ray technology that produces cross-sectional images of the brain. Scanning is painless and quick but also requires lying still. CT scans expose patients to a small amount of radiation and show less detail than MRI scans. CT scans for hydrocephalus are usually used only in emergency situations.^[9]

Treatment

Hydrocephalus is typically treated with surgery. The goal of treatment is to reduce the pressure on the brain by managing the buildup of cerebrospinal fluid.^[9][10]

Shunt surgery

The most common treatment is shunt surgery. During this procedure, a thin tube called a shunt is implanted in the brain. The shunt allows excess CSF to drain from the brain to another part of the body, usually the abdomen, where it can be absorbed into the bloodstream.^[10]

Inside the shunt is a valve that controls how quickly the fluid drains, preventing it from draining too fast. The valve can be felt as a small lump under the skin on the scalp. Shunt surgery is performed by a specialist in brain and nervous system surgery called a neurosurgeon. The operation is done under general anesthesia and typically takes one to two hours. Most patients need to stay in the hospital for a few days after surgery to recover.^[10]

After a shunt is placed, further treatment may be needed if the shunt becomes blocked or infected. In these cases, shunt repair surgery will be necessary.^[10]

Endoscopic third ventriculostomy (ETV)

An alternative to shunt surgery is a procedure called endoscopic third ventriculostomy. Instead of inserting a shunt, the surgeon makes a small hole in the floor of the brain to allow trapped CSF to escape to the brain’s surface, where it can be absorbed naturally. This procedure avoids the blockage that is causing the hydrocephalus.^[10]

ETV is not suitable for everyone. It works best when the buildup of CSF is caused by a blockage in the fluid pathways, a condition called obstructive hydrocephalus. The procedure is done under general anesthesia. The neurosurgeon makes a small opening in the skull and brain and uses an endoscope (a long, thin tube with a light and camera) to see inside the brain chambers and create the drainage hole. The procedure takes about one hour.^[10]

There is a lower risk of infection after ETV compared to shunt surgery. However, as with shunts, there is a risk that a blockage may develop months or years after surgery, which would cause symptoms to return.^[10]

Other treatment options

In some cases, removing the cause of hydrocephalus can cure the condition. For example, if a brain tumor is blocking CSF flow, removing the tumor cures the hydrocephalus in about 80% of cases.^[13]

Medical treatment with medications can sometimes be used as a temporary measure, especially in premature infants with bleeding-related hydrocephalus, to delay the need for surgery. However, medications are not effective for long-term treatment of chronic hydrocephalus.^[13]

Who can be affected

Hydrocephalus can occur at any age, but it is most common in infants and adults aged 60 and older. About one to two out of every 1,000 babies in the United States are born with hydrocephalus. Many of these cases are diagnosed before birth, at the time of delivery, or in early childhood.^[8]

Normal pressure hydrocephalus affects about 6% of people over 80 years of age. The condition can also develop in children and adults of all ages due to injury, infection, bleeding, or tumors.^[5]

Without treatment, hydrocephalus can cause permanent brain damage or death. However, with proper treatment, many people with hydrocephalus live normal lives, though there are risks of complications such as infection or shunt malfunction.^[1][3]