Hydrocephalus
Hydrocephalus is a condition in which excess cerebrospinal fluid (CSF) builds up within the fluid-containing cavities or ventricles of the brain.
CSF is in constant circulation within the ventricles of the brain and serves many crucial functions:
1) it acts as a “shock absorber” for the brain and spinal cord;
2) it acts as a vehicle for delivering nutrients to the brain and removing waste from it;
3) it flows between the cranium and spine to regulate changes in pressure.
When CSF builds up around the brain, it can create harmful pressures on the tissues of the brain confined within the skull. The accumulation of CSF occurs due to either an increase in production of the fluid, a decrease in its rate of absorption or from a condition that blocks its normal flow through the ventricular system.
Causes of Hydrocephalus
Some cases of hydrocephalus are present at birth, while others develop in childhood or adulthood. Hydrocephalus can be inherited genetically, may be associated with developmental disorders, like spina bifida or encephalocele, or occur as a result of brain tumors, head injuries, hemorrhage or diseases such as meningitis. Based on onset, presence of structural defects or high vs. normal CSF pressures, hydrocephalus can be divided into categories.
Acquired Hydrocephalus: This is the type of hydrocephalus that develops at birth or in adulthood and is typically caused by injury or disease.
Congenital Hydrocephalus: It is present at birth and may be caused by events that occur during fetal development or as a result of genetic abnormalities.
Communicating Hydrocephalus: This type of hydrocephalus occurs when there is no obstruction to the flow of CSF within the ventricular system. The condition arises either due to inadequate absorption or due to an abnormal increase in the quantity of CSF produced.
Non-communication (Obstructive) Hydrocephalus: It occurs when the flow of CSF is blocked along one of more of the passages connecting the ventricles, causing enlargement of the pathways upstream of the block and leading to an increase in pressure within the skull.
Normal Pressure Hydrocephalus: It is a form of communicating hydrocephalus that can occur at any age, but is most common in the elderly. It is characterized by dilated ventricles with normal pressure within the spinal column.
Hydrocephalus Ex-vacuo: It primarily affects adults and occurs when a degenerative disease, like Alzheimer’s disease, stroke or trauma, causes damage to the brain that may cause the brain tissue to shrink.
Symptoms of Hydrocephalus
The symptoms of hydrocephalus tend to vary greatly from person to person and across different age groups. Infants and young children are more susceptible to symptoms from increased intracranial pressure like vomiting and adults can experience loss of function like walking or thinking.
Infants
- Unusually large head size
- Rapidly increasing head circumference
- Bulging and tense fontanelle or soft spot
- Prominent scalp veins
- Downward deviation of eyes or sunset sign
- Vomiting
- Sleepiness
- Irritability
- Seizures
Children and Adolescents
- Nausea and vomiting
- Swelling of the optic disc or papilledema
- Blurred or double vision
- Balance and gait abnormalities
- Slowing or loss of developmental progress
- Changes in personality
- Inability to concentrate
- Seizures
- Poor appetite
- Urinary incontinence
Adults
- Headache
- Nausea and vomiting
- Difficulty walking or gait disturbances
- Loss of balance or coordination
- Lethargy
- Bladder incontinence
- Impaired vision
- Impaired cognitive skills
- Memory loss
- Mild dementia
Diagnosis of Hydrocephalus
If the doctor suspects hydrocephalus, he performs a thorough clinical evaluation, including reviewing and recording a detailed patient history and performing a physical exam to assess the condition. A complete neurological examination, including one of more of the following tests, is usually recommended to confirm the diagnosis and assess for treatment options:
- Computed tomography scan (CT or CAT scan)
- Magnetic resonance imaging (MRI)
- Lumbar puncture (spinal tap)
- Intracranial pressure monitoring
- Isotope cisternography
Treatment of Hydrocephalus
Based on the underlying etiology, the condition may be treated directly by removing the cause of CSF obstruction or indirectly by diverting the excess fluid. Hydrocephalus is most commonly treated indirectly by implanting a device known as a “shunt” to divert the excess CSF away from the brain. The shunt is a flexible tube which, along with a catheter and a valve, is placed under the skin to drain excess CSF from a ventricle inside the brain to another body cavity such as the peritoneal cavity (the area surrounding the abdominal organs).
Once inserted, the shunt system usually remains in place for the duration of a patient’s life (although additional operations to revise the shunt system are sometimes needed). The shunt system continuously performs its function of diverting the CSF away from the brain, thereby keeping the intracranial pressure within normal limits. In some cases, two procedures are performed, the first to divert the CSF and another at a later stage to remove the cause of obstruction (e.g. a brain tumor).
A limited number of patients can be treated with an alternative operation called endoscopic third ventriculostomy. In this procedure, a surgeon utilizes a tiny camera (endoscope) with fiber optics to visualize the ventricles and create a new pathway through which CSF can flow.
