Hydrocephalus

Risk factors for hydrocephalus may include birth defects in the brain and spinal cord, developmental issues resulting from premature birth or genetic factors, or infection and injury. Certain conditions, such as spina bifida or meningitis, can increase the risk of developing hydrocephalus, especially in infants and children.  

Congenital hydrocephalus is present at birth and may be caused by infections during pregnancy, hereditary factors, or developmental issues in the brain and spinal cord. In cases of congenital hydrocephalus, the ventricles (cavities) in the brain are often blocked and unable to effectively drain CSF.

Acquired hydrocephalus develops after birth and can result from various factors, including infections like meningitis or encephalitis, brain tumors, head injury, and bleeding in the brain or skull. In these cases, swelling or pressure inside the skull can block the pathways that allow CSF to flow through the brain and spinal cord.

There are several different types of hydrocephalus, which can be acquired or congenital:

Non-Communicating (Obstructive) Hydrocephalus

This type of hydrocephalus occurs when CSF can no longer flow through the ventricles in the brain because one or more of the passages between ventricles are blocked. Brain tumors are a common cause of obstructive hydrocephalus.

Communicating Hydrocephalus

This type of hydrocephalus occurs when the brain’s ventricles remain open and CSF can still flow through them like normal, but the ability of smaller blood vessels to absorb CSF after it leaves the ventricles is impaired. Brain trauma and bleeding inside the skull are significant risk factors for communicating hydrocephalus. 

Normal Pressure Hydrocephalus (NPH)

This is a common type of communicating hydrocephalus that occurs when CSF is blocked from flowing normally through the brain and spinal cord and the ventricles in the brain are enlarged, but with no significant increase in pressure inside the skull. The exact cause of NPH is often unclear, but risk factors include age, a history of traumatic brain injury, and some underlying medical conditions. Because it typically occurs in older adults and symptoms include difficulty with thinking and memory, NPH is often confused with Alzheimer’s disease.

Hydrocephalus Ex-Vacuo

This is not a true form of hydrocephalus, but rather occurs when a brain injury, stroke, or neurodegenerative disease like Alzheimer’s causes tissues around the ventricles to shrink and the ventricles to enlarge. For this reason, the ventricles appear enlarged and there may be an excess of CSF, but pressure in the brain remains normal.

Hydrocephalus symptoms may vary depending on the cause and the age of the person affected. Some common signs of hydrocephalus include:

• Headache
• Nausea and vomiting
• Blurred or double vision
• Problems with coordination, balance, and motor skills
• Irritability and changes in mood
• Difficulty concentrating
• Memory problems
• Seizures

Infants with hydrocephalus may also seem excessively sleepy or have difficulty staying awake. In some cases, the fontanel—the soft spot on the top of a baby’s head—may be visibly swollen or have a bulging appearance. Older adults who develop normal pressure hydrocephalus may experience incontinence or difficulty controlling the urge to urinate.

Symptoms of hydrocephalus may mimic those of other conditions, which can make it difficult to diagnose. In adult cases, doctors will typically first conduct a clinical examination to evaluate coordination, muscle strength and reflexes, vision, and cognitive function. Additional testing and brain imaging may be used to rule out other possible causes of symptoms, including a CT scan, MRI, or angiogram (an X-ray of the blood vessels in the brain). In some cases, a fetal ultrasound may be used to diagnose hydrocephalus before birth.

In some cases, doctors may order a spinal tap to estimate CSF pressure or insert an intracranial pressure monitor into the brain to measure pressure inside the ventricles. Because these are invasive surgical procedures, they are done in a hospital setting and usually followed by an extended observation period where doctors can monitor symptoms and changes in pressure inside the skull.

If left untreated, hydrocephalus can result in developmental disorders and cognitive impairment, and it is eventually fatal. Children who are treated for hydrocephalus can make a full recovery and often benefit from rehabilitation programs to bridge any developmental delays. 

Standard treatments for hydrocephalus involve surgically placing a tube (called a shunt) in the brain in order to drain excess cerebrospinal fluid. In these cases, the shunt redirects excess fluid out of the skull, where it is eventually reabsorbed by the body. People who undergo this surgery typically require long-term monitoring to ensure the shunt is functioning properly, and in some cases follow-up surgeries may be needed to repair or replace shunts that have become clogged. Children who were treated for hydrocephalus may also require additional surgeries to lengthen the shunt system as they grow. 

In cases where hydrocephalus is caused by another medical condition such as infection, tumor, or internal bleeding in the brain, doctors may treat the root cause first to determine if this alleviates hydrocephalus symptoms. For example, this may involve surgery to remove a tumor or treating an infection with antibiotics.

Current research on hydrocephalus is focused on better understanding how the condition impacts early brain development and identifying early signs of illness. Research on the impact of inflammation on the brain may also provide clues about how to treat both hydrocephalus and underlying conditions like autoimmune disorders.

Additionally, researchers are exploring less invasive ways to treat hydrocephalus, strategies for promoting healing and recovery for damaged brain tissue, and connections between cognitive symptoms of hydrocephalus and neurodegenerative diseases like Alzheimer’s.