What is hydrocephalus?
The normal brain has several cavities or ventricles that contain a clear fluid called cerebrospinal fluid (CSF). This fluid circulates from within the ventricles to around the brain and the spinal cord and is finally absorbed into the blood stream. An excessive accumulation of CSF in the ventricles results in a ballooning of the ventricles that is called hydrocephalus (Greek "hydro" meaning water and "cephalus" meaning head). This ballooning puts pressure on the surrounding brain affecting its function and producing symptoms.
Normally, there is a critical balance between rate of production and absorption of CSF. Hydrocephalus results if there is an overproduction of CSF or there is a block in its normal flow or absorption.
What are the different types of hydrocephalus?
Hydrocephalus may be congenital (since birth) or acquired. It may also be categorized as communicating or non-communicating. Communicating hydrocephalus occurs when the flow of CSF is blocked after it exits the ventricles as in certain infections like meningitis. Non-communicating hydrocephalus - also called "obstructive" hydrocephalus - occurs when the flow of CSF is blocked along the narrow communications between the ventricles. This is the commonest type of congenital hydrocephalus and may also occur because of brain tumours.
Hydrocephalus ex-vacuo occurs when stroke or traumatic injury cause damage to the brain. In these cases, brain tissue may actually shrink. Normal pressure hydrocephalus can happen to people at any age, but it is most common among the elderly. It may result from a subarachnoid hemorrhage, head trauma, infection, tumor, or complications of surgery. However, many people develop normal pressure hydrocephalus even when none of these factors are present for reasons that are unknown.
What causes hydrocephalus?
The causes of congenital hydrocephalus are not well understood. It may also be associated with neural tube defects including spina bifida and encephalocele). Other possible causes include complications of premature birth such as intraventricular hemorrhage, diseases such as meningitis, tumours, head injury, or subarachnoid hemorrhage, which block the exit of CSF from the ventricles to the cisterns or eliminate the passageway for CSF into the cisterns.
What are the symptoms?
Symptoms of hydrocephalus vary with age and the underlying cause, if any. In infants, it commonly presents with a rapid increase in head circumference or an unusually large head size. The joints in the bones of an infant’s skull have not closed, and so the skull can expand to accommodate the buildup of CSF. Other symptoms may include vomiting, sleepiness, irritability, downward deviation of the eyes (also called "sunsetting"), and seizures.
Once these joint sutures close, pressure builds up inside the skull resulting in headache followed by vomiting, nausea, convulsions, papilloedema (swelling of the nerve in the eye), blurred or double vision, problems with balance, poor coordination, gait disturbance, urinary incontinence, slowing or loss of developmental progress, lethargy, drowsiness, irritability, or other changes in personality or cognition including memory loss. These are the usual symptoms in older children and adults.
How is hydrocephalus diagnosed?
Hydrocephalus is diagnosed through clinical neurological evaluation and by using cranial imaging techniques such as ultrasonography in infants, computed tomography (CT), magnetic resonance imaging (MRI), or pressure-monitoring techniques. A physician may aso examine the inside of the eye, called fundoscopy to look for papilloedema. He may select the appropriate diagnostic tool based on an individual’s age, clinical presentation, and the presence of known or suspected abnormalities of the brain or spinal cord.
What is the treatment?
The definitive treatment of hydrocephalus is the surgical insertion of a shunt system. This device diverts the flow of CSF from the brain to another area of the body where it can be absorbed.
A shunt is made of a flexible plastic tube with a valve mechanism. One end of the catheter is placed within a ventricle inside the brain or in the CSF outside the spinal cord. The other end of the catheter is commonly placed within the abdominal cavity, but may also be placed at other sites in the body such as a chamber of the heart or areas around the lung where the CSF can drain and be absorbed. A valve located along the catheter maintains one-way flow and regulates the rate of CSF flow.
An alternative surgical procedure is called third ventriculostomy. In this procedure, a thin optical instrument called neuroendoscope is inserted into the brain that allows the doctor to view the ventricular system from within. Once the scope is guided into position, a tiny hole is made in the floor of the third ventricle, which allows the CSF to bypass the obstruction and flow toward the site of absorption around the surface of the brain. This technique is useful only in selective cases of obstructive or non-communicating hydrocephalus.
What are the complications of shunt surgery?
Shunt systems are mechanical devices. They may have mechanical failures leading to other problems such as overdraining or underdraining of CSF. Sudden overdrainage and underdrainage, both may produce symptoms. With the growth of this child, the tubing may become short, needing replacement. The shunt system may get blocked or infected. Generally, shunt systems require monitoring and regular medical follow up.
What is the outcome?
The prognosis for patients with hydrocephalus is variable depending on the age of development, cause of hydrocephalus, the nature of treatment and complications of shunt surgery, if any. It is not certain whether the decrease in CSF pressure following shunt surgery will significantly reverse the damage to the brain. Some patients, with passage of time may no longer require a functioning shunt. Most others develop symptoms again if the shunt malfunctions and need reoperation to replace the shunt.