What is Hydrocephalus?
Hydrocephalus is a condition characterized by excessive accumulation of cerebrospinal fluid (CSF) in and around the brain, which causes swelling of the brain and affects normal brain function.
CSF is the fluid that surrounds the brain and the spinal cord. It is produced by hollow spaces inside the brain called ventricles. The fluid protects your brain and spinal cord from injury by functioning as a cushion. Usually, CSF drains out of the brain through the ventricles and into the spinal column, which is then absorbed by the body. However, if the circulatory path of the CSF becomes obstructed and the fluid cannot drain out properly, the fluid accumulates causing the ventricles to swell and pressure inside the head to increase, resulting in hydrocephalus.
Hydrocephalus can occur at any age but is more common in infants and adults over the age of 60. Hydrocephalus may be congenital or acquired in origin. Congenital hydrocephalus is present at birth and may be caused by genetic abnormalities or abnormalities in fetal development during pregnancy. Acquired hydrocephalus occurs over time due to injury or disease and can affect individuals of all ages.
Types of Hydrocephalus
Hydrocephalus is mainly categorized into two types:
- Communicating hydrocephalus or non-obstructive hydrocephalus: Communicating hydrocephalus occurs when the flow of cerebrospinal fluid is obstructed after it leaves the ventricles. The term “communicating” refers to the fact that the fluid can still flow between the ventricles, which remain open. Communicating hydrocephalus can also be subcategorized into normal pressure hydrocephalus (NPH) and hydrocephalus ex-vacuo.
- Non-communicating hydrocephalus or obstructive hydrocephalus: Non-communicating hydrocephalus occurs when the flow of cerebrospinal fluid is obstructed along one or more of the narrow passageways connecting the ventricles. One of the most common causes of this is a condition known as aqueductal stenosis, a narrowing of the aqueduct of Sylvius, a small passageway between the 3rd and 4th ventricles in the middle of the brain.
Normal Pressure Hydrocephalus (NPH): NPH is a form of communicating hydrocephalus and primarily affects individuals in their 60s and 70s. It may occur as a result of a bleeding in the brain, head trauma, infection, tumor, or a complication of surgery. However, NPH can also occur when none of these factors are involved. Contrary to other types of hydrocephalus, the increase in cerebrospinal fluid in NPH occurs slowly enough that the tissues around the ventricles compensate and the fluid pressure within the head does not increase alarmingly.
Hydrocephalus ex-vacuo: This is another form of communicating hydrocephalus that primarily affects adults and results from brain damage due to injury or stroke. In hydrocephalus ex-vacuo, brain tissues around the ventricles shrink, and the ventricles appear larger than normal due to this.
Causes of Hydrocephalus
Most cases of hydrocephalus are idiopathic (unknown cause) as it is unclear what exactly causes the absorptive pathways of the fluid to become obstructed. However, the condition can also occur as a result of known causes such as:
- Head injury
- Inherited genetic abnormalities
- Complications during childbirth
- Complications during cranial surgery
- Tumor or cysts
- Subarachnoid or intraventricular hemorrhage
- Subdural hematomas
- Meningitis/other brain infections
Signs and Symptoms of Hydrocephalus
Hydrocephalus is a progressive medical condition and symptoms worsen over time. These symptoms include:
- Difficulty walking/unsteady gait
- Loss of bladder control
- Dementia and mental impairment
- Abnormal head enlargement
- Nausea or vomiting
- Vision problems
- Poor coordination and balance
Diagnosis of Hydrocephalus
It is quite challenging to diagnose hydrocephalus as symptoms are identical to those of other neurological disorders, such as Parkinson’s disease, Alzheimer’s disease, and Creutzfeldt-Jakob disease. In order to diagnose the condition, your physician will review your medical history and conduct a thorough neurological examination to evaluate muscle strength and reflexes, coordination and balance, and mental functioning. Imaging studies such as an ultrasound, magnetic resonance imaging (MRI), or computed tomography (CT) scans of the brain will be ordered to look for signs of enlarged ventricles or pathway obstruction. Other tests such as a lumbar catheter (spinal tap), fundoscopic examination, and intracranial pressure monitoring will also be ordered to accurately diagnose hydrocephalus and rule out other similar conditions.
Treatment for Hydrocephalus
The standard treatment employed for hydrocephalus is the surgical placement of a shunt, a device that directs the cerebrospinal fluid away from the blocked pathway of the brain to another pathway where it can be drained and absorbed by the body.
The most common area of the body utilized for drainage of the cerebrospinal fluid is the abdominal (peritoneal) cavity, and the most common shunt system utilized to create this drainage is the ventriculoperitoneal (VP) shunt, which enables drainage of excess cerebrospinal fluid from the cerebral ventricles to the peritoneum area. Alternatively, the drainage catheter can also be positioned in a vein that leads to the heart. This is known as ventriculoatrial (VA) shunt. VA shunts are less common than VP shunts. Most shunt systems are comprised of 3 parts:
- A collection catheter located inside the cerebral ventricles
- A regulatory valve to control the flow of cerebrospinal fluid
- An exit catheter for the drainage of cerebrospinal fluid to another area of the body where it is can be absorbed
VP shunt surgery is performed under general anesthesia and takes about 90 minutes to complete. In general, the procedure involves:
- A surgical cut is made on the scalp behind the head to expose the skull.
- A drill is used to make a small hole on the skull to expose the brain.
- A catheter is passed through the brain and is positioned inside the enlarged ventricles.
- A small cut is made at the back of the ear to insert a valve/shunt and a ventricular catheter is attached to it.
- One more cut is made in the abdominal area. A passageway is created underneath the skin from the back of the ear, passing down the neck and chest and into the belly area.
- A peritoneal catheter is attached to the valve/shunt to transfer the excess CSF to the peritoneum.
After the VP shunt placement is complete, the excess fluid drains out into the belly area where it will be absorbed as part of a normal circulatory process. This drainage by shunt enables the swollen ventricles to return to their normal size, reduces intracranial pressure, and eliminates all symptoms associated with the condition.
For some patients who have normal pressure hydrocephalus or aqueductal stenosis, a procedure called endoscopic third ventriculostomy (ETV) can be used as an alternative treatment to VP shunt placement. The ETV procedure involves making a dime-sized hole in the skull and creating an opening in the floor of the third ventricle in the brain. This allows the entrapped cerebrospinal fluid inside the brain's ventricles to bypass the blockage and escape into the newly created pathway where the fluid gets absorbed. Endoscopic refers to the surgery being performed utilizing an endoscope - a thin, flexible fiber-optic tube with a camera, light, magnifying lens, and a port to pass tiny instruments. This procedure can be effective in both communicating and obstructive hydrocephalus and applied to both adults and children.