Hydrocephalus
What is Hydrocephalus?
Hydrocephalus is a condition of excess fluid on the brain. The brain and spinal cord are normally bathed by cerebrospinal fluid (CSF) which gives the brain buoyancy and acts as a shock-absorber to protect these delicate structures.
CSF is produced in fluid-filled structures called ventricles. The brain has four ventricles: two lateral ventricles connected to the third ventricle via the foramina of Munro. This drains into the fourth ventricle via the cerebral aqueduct (Aqueduct of Sylvius). The fluid then leaves the fourth ventricle, bathes the entire brain and spinal cord and is absorbed back into the blood stream via arachnoid granules along the venous sinuses.
The CSF is produced by the “choroid plexus.” This structure lines all four ventricles and produces enough fluid to cycle through the entire central nervous system at least three times per day.
Unfortunately, there is no off switch to stop this process. Hence, if there is blockage along the drainage pathway or if the fluid cannot be absorbed back into the blood, then the fluid is backed-up into the ventricles, causing enlargement – a.k.a. Hydrocephalus.
What Causes Hydrocephalus?
There are numerous causes of hydrocephalus that occur in adults. One can be born with an obstruction (aqueductal stenosis) and in utero or developmental events can result in some versions of hydrocephalus. Conversely, one can have a cerebral disease that results in hydrocephalus including meningitis, hemorrhage (brain bleed), traumatic brain injury, brain tumors or CSF spread of cancer cells (leptomeningeal carcinomatosis).
Hydrocephalus Symptoms
Symptoms of hydrocephalus range from:
- Memory difficulties
- Walking difficulties
- Incontinence
- Vision disturbances
- Headaches
- Nausea
- Vomiting
- Seizures
- Altered mental status in more acute cases
Basic brain imaging including CT scan of the head and brain MRI are necessary to make this diagnosis. Though there are some medications that can slow this fluid production, there is no medical way to stop production as of yet.
Diagnosis and Treatment
Treatment includes diversion of the CSF to other parts of the body. This can be done in a variety of methods and is tailored to the type of hydrocephalus. Hydrocephalus diagnoses include:
The different types of hydrocephalus are categorized based on their causes and the flow dynamics of the CSF. Below is a breakdown of the differences:
1. Normal Pressure Hydrocephalus (NPH)
- Definition: NPH is a type of hydrocephalus that occurs mainly in older adults causing dementia-like symptoms, where CSF builds up in the brain’s ventricles, but the pressure inside the brain remains normal, hence the name “normal pressure.”
- Symptoms: The classic triad of symptoms includes:
- Gait disturbance: Difficulty walking, often described as shuffling or unsteady.
- Cognitive impairment: Memory loss, confusion, and difficulty in thinking, resembling dementia.
- Urinary incontinence: Loss of bladder control, leading to frequent urination or the inability to hold urine.
- Cause: The exact cause is often unclear but may be related to impaired CSF absorption, leading to gradual accumulation without significant pressure elevation.
- Treatment: The most common treatment is the placement of a shunt to drain excess fluid from the brain to another part of the body.
2. Obstructive Hydrocephalus (Non-communicating Hydrocephalus)
- Definition: This type of hydrocephalus occurs when there is a physical blockage in the flow of CSF within the ventricular system, preventing it from circulating properly.
- Symptoms: Depending on the location and severity of the blockage, symptoms can include:
- Headaches
- Nausea and vomiting
- Vision problems
- Difficulty with balance and coordination
- Cognitive changes
- Cause: The blockage can be caused by congenital malformations, tumors, cysts, or infections.
- Treatment: Surgical interventions, such as the removal of the obstruction or the placement of a shunt, are common treatments.
3. Communicating Hydrocephalus
- Definition: In communicating hydrocephalus, CSF can still flow between the ventricles, but its absorption into the bloodstream is impaired, leading to fluid buildup.
- Symptoms: Similar to obstructive hydrocephalus but can vary widely depending on the underlying cause and the age of the patient. Symptoms may include:
- Increased head size in infants
- Headaches
- Nausea and vomiting
- Cognitive difficulties
- Vision problems
- Cause: Causes can include infections (like meningitis), hemorrhage, or head trauma, which damage the brain’s ability to absorb CSF.
- Treatment: Treatment often involves the surgical placement of a shunt to divert excess fluid or an endoscopic third ventriculostomy (ETV), where a small hole is made in the floor of the third ventricle to allow CSF to bypass the obstruction.
Summary of Differences:
- NPH is unique in that it primarily affects older adults, and the pressure in the ventricles remains normal despite fluid buildup.
- Obstructive Hydrocephalus is caused by a physical blockage that prevents CSF from circulating, leading to increased pressure in the brain.
- Communicating Hydrocephalus involves impaired absorption of CSF, but there is no blockage in the ventricular system.
Understanding these differences is essential for proper diagnosis and treatment, as each type of hydrocephalus requires a different approach.
