Hydrocephalus is a medical condition involving the abnormal accumulation of cerebrospinal fluid (CSF) within the brain’s internal cavities, or ventricles. This fluid buildup causes the ventricles to enlarge, which then puts harmful pressure on the surrounding brain tissue.
Hydrocephalus: Understanding the Mechanics of Fluid Buildup
The fluid involved is cerebrospinal fluid (CSF), a clear, colorless liquid that surrounds the brain and spinal cord. CSF acts as a shock absorber to cushion the brain and serves as a vehicle for nutrient delivery and waste removal. The brain continuously produces this fluid within the ventricles, primarily by the choroid plexus.
Normally, the body produces and reabsorbs an equal amount of CSF each day, maintaining a balanced pressure. The fluid circulates through the four ventricles and then flows into the spaces around the brain and spinal cord before being absorbed through structures known as arachnoid villi. Hydrocephalus occurs when this delicate balance is disrupted, typically due to an obstruction in the flow pathway, an issue with absorption, or an overproduction.
When flow or absorption is impaired, excess CSF causes the ventricles to swell, leading to increased intracranial pressure. This sustained pressure can compress and damage the brain tissue, impairing normal function. The location of the disruption determines the type of hydrocephalus, which can be categorized as communicating (absorption issue) or non-communicating (flow blockage).
Triggers for Hydrocephalus (Causes and Risk Factors)
Hydrocephalus can be broadly categorized based on its onset, being either congenital or acquired. Congenital hydrocephalus is present at birth, often resulting from genetic factors or events during fetal development. A common congenital cause is aqueductal stenosis, a narrowing of the small passage between the third and fourth ventricles that blocks CSF flow.
Developmental disorders, such as spina bifida and other neural tube defects, can also cause the condition by structurally altering the brain and spinal cord. Infections the mother contracts during pregnancy, like rubella or toxoplasmosis, are risk factors as they can cause inflammation in the fetal brain tissue. Complications of premature birth, specifically intraventricular hemorrhage (bleeding within the ventricles), are another significant factor in newborns.
Acquired hydrocephalus develops after birth, usually as a consequence of injury or disease. The most frequent acquired causes include head trauma, which can lead to bleeding in the brain. Central nervous system infections, such as bacterial meningitis, can cause inflammation and scarring that impairs CSF absorption. Brain tumors or cysts can also block the pathways through which the CSF must travel, leading to an obstructive form of the condition.
Recognizing the Symptoms and Confirming Diagnosis
The symptoms of hydrocephalus vary significantly depending on the patient’s age and how well their skull bones have fused. In infants, whose skull sutures are not yet closed, the skull can expand to accommodate the increased fluid, leading to visible changes. Signs in babies include an unusually large head size or a rapid increase in head circumference, as well as a bulging or tense soft spot, known as the fontanel.
Infants may also exhibit physical signs of distress, such as vomiting, excessive sleepiness, irritability, and poor feeding. A distinctive symptom is the “sunsetting” of the eyes, where the eyes are fixed downward and cannot turn outward.
In older children and adults, whose skulls are rigid and cannot expand, the symptoms are primarily related to increased intracranial pressure. These patients often experience headaches, nausea, vomiting, and vision problems, including blurred or double vision. They may also show cognitive changes, such as difficulty concentrating, a decline in school or work performance, and issues with coordination and balance.
Diagnosis relies on a neurological evaluation combined with advanced brain imaging techniques. Computer tomography (CT) scans and Magnetic Resonance Imaging (MRI) are commonly used to visualize the enlarged ventricles and identify any structural cause of the blockage. In infants, a cranial ultrasound can sometimes be used to detect the condition before the fontanel closes.
Treatment and Long-Term Management Strategies
The goal of hydrocephalus treatment is to relieve pressure on the brain by diverting or reducing the excess cerebrospinal fluid. The most common surgical intervention is the placement of a shunt, which is a flexible tube system that redirects the CSF to another area of the body for absorption. A ventriculoperitoneal (VP) shunt is the most frequent type, draining the fluid from the brain’s ventricles into the abdominal cavity, where it is absorbed by the body’s vascular system.
Shunt placement is an effective intervention, but it requires lifelong monitoring and carries the risk of complications. The most common issues are shunt malfunction, often due to blockage, and infection, which can be serious. Shunt failure frequently necessitates repeat surgeries, with a significantly higher revision rate observed in pediatric patients compared to adults.
An alternative procedure for certain patients with obstructive hydrocephalus is the Endoscopic Third Ventriculostomy (ETV). In this surgery, a small hole is created in the floor of the third ventricle, allowing the CSF to bypass the obstruction and flow into the spaces where it can be absorbed. ETV is preferred as it avoids implanting foreign material and can have a lower long-term complication rate than a shunt.
Long-term management of hydrocephalus extends beyond surgical intervention, requiring ongoing neurological follow-up to monitor the shunt or ETV function. Patients may also benefit from rehabilitative therapies, such as occupational and physical therapy, to manage and improve any residual physical or cognitive symptoms.