Abnormal fluid accumulation in the brain occurs when excess fluid builds up inside or around the brain. This buildup can lead to increased pressure within the skull, potentially affecting brain function. Understanding this condition requires recognizing normal brain fluid processes and how disruptions lead to such accumulations.
The Brain’s Essential Fluid
The brain and spinal cord are surrounded by a clear, colorless liquid called cerebrospinal fluid (CSF). CSF is primarily produced by specialized tissue called the choroid plexus, located within the brain’s ventricles, which are interconnected cavities deep inside the brain. An adult typically has about 150 milliliters of CSF, with approximately 500 milliliters produced daily. This fluid constantly circulates through the ventricles, around the brain’s surface, and down the spinal cord.
CSF serves several functions, including cushioning the brain and spinal cord from injury, providing buoyancy so the brain feels lighter within the skull, delivering nutrients, and removing waste products. After circulating, CSF is reabsorbed into the bloodstream, primarily through structures called arachnoid granulations. This continuous production, circulation, and absorption maintain a balanced fluid environment.
When Fluid Accumulates Abnormally
Abnormal fluid accumulation in the brain often refers to hydrocephalus, where excessive CSF builds up within the brain’s ventricles. This excess fluid causes the ventricles to enlarge, putting harmful pressure on the surrounding brain tissues. Hydrocephalus can be classified as communicating or non-communicating (obstructive). Communicating hydrocephalus occurs when CSF flow is blocked after it leaves the ventricles, often due to impaired absorption. Non-communicating hydrocephalus results from a blockage within the narrow passages connecting the ventricles.
Another form of abnormal fluid accumulation is cerebral edema, which involves excess fluid in the intracellular or extracellular spaces of the brain tissue. Cerebral edema is essentially brain swelling and can occur in specific areas or throughout the brain. This condition increases intracranial pressure, which can prevent oxygen-rich blood from reaching brain cells and cause further damage.
Underlying Reasons for Buildup
The causes of hydrocephalus are varied and involve an imbalance between CSF production and absorption, or an obstruction in its flow. Impaired CSF absorption is a frequent cause of communicating hydrocephalus, often resulting from post-hemorrhagic or post-inflammatory changes, such as those seen after a subarachnoid hemorrhage or meningitis. These conditions can block the arachnoid granulations responsible for CSF reabsorption. Overproduction of CSF is a rare cause, sometimes linked to tumors.
Obstructive hydrocephalus arises when CSF flow is blocked along the pathways connecting the ventricles. Common obstructions include birth defects or acquired conditions like tumors, infections, or hemorrhage. Hydrocephalus can be congenital, present at birth due to developmental or genetic factors, or acquired later in life from injury or disease. Normal pressure hydrocephalus (NPH) often affects the elderly, where CSF builds up slowly, leading to enlarged ventricles with little to no increase in intracranial pressure.
Cerebral edema can be triggered by acute brain injuries and medical conditions. Common causes include traumatic brain injury, which can disrupt the blood-brain barrier and lead to fluid leakage into brain tissue. Strokes, both ischemic and hemorrhagic, are frequent causes, as they can damage brain cells and lead to swelling. Brain tumors, infections such as meningitis or encephalitis, and even high altitude can also contribute to cerebral edema.
Signs and Indications
Symptoms of abnormal fluid accumulation in the brain vary depending on age, underlying cause, and how quickly fluid builds up. In infants, whose skull bones have not yet fused, signs often include a rapid increase in head size or an unusually large head circumference. Other indications in babies can be a bulging soft spot (fontanelle) on the top of the head, vomiting, irritability, and excessive sleepiness. Sometimes, their eyes may appear fixed downward, a phenomenon known as “sun setting” eyes.
Older children and adults experience symptoms related to increased pressure within the rigid skull. Common signs include headaches, nausea, and vomiting. Vision problems, such as blurred or double vision, can also occur. Other symptoms include issues with balance and coordination, changes in personality, memory loss, or a decline in cognitive function. Lethargy, difficulty waking up, and seizures are possible in more severe cases.
Medical Assessment and Care
Diagnosing abnormal fluid accumulation in the brain begins with a neurological examination, where healthcare providers assess muscle strength, reflexes, coordination, balance, and mental functioning. Imaging techniques are crucial for confirmation and include ultrasounds, computed tomography (CT) scans, and magnetic resonance imaging (MRI). Ultrasounds are often used for infants with open fontanelles, while CT and MRI scans provide detailed images of the brain and detect enlarged ventricles or fluid within brain tissue. In some cases, a lumbar puncture (spinal tap) may be performed to measure CSF pressure and analyze the fluid.
Treatment approaches depend on the specific condition and its cause. For hydrocephalus, surgical interventions are the primary treatment. The most common procedure involves implanting a shunt, a flexible tube that drains excess CSF from the brain to another part of the body, such as the abdomen, where it can be absorbed. Another surgical option for certain types of obstructive hydrocephalus is an endoscopic third ventriculostomy (ETV), where a small hole is created in the floor of the third ventricle to allow CSF to bypass a blockage.
For cerebral edema, treatment focuses on reducing brain swelling and addressing the underlying cause. Medications, such as corticosteroids or diuretics, may decrease fluid buildup. Surgical decompression might be necessary to relieve pressure on the brain. Treating the root cause, such as removing a tumor, managing an infection, or addressing a head injury, is a central part of the care plan.