Anatomy
What is Hydrocephalus?
Hydrocephalus, as found in children or adults, is a condition resulting from the enlargement of one or more of the ventricles of the brain due to an
excess of cerebral spinal fluid. There are three basic categories of hydrocephalus: Adult, Childhood, and Idiopathic. The differences between adult
or idiopathic hydrocephalus and childhood hydrocephalus are large enough to separate the two entirely because of the developmental stages of the brain
in early childhood. Cases of idiopathic hydrocephalus are grouped together as “idiopathic” because their cause is unknown. We will be focusing on adult
hydrocephalus and adult idiopathic hydrocephalus.
Adult Hydrocephalus
The build up of excess cerebral spinal fluid can originate from a variety of sources, but the most common reason for hydrocephalus to develop is that
something is blocking the flow of fluid through the brain. The obstruction can be caused by many causes. The idiopathic group and those from subarachnoid
hemorrhage are considered the leading causes of adult hydrocephalus.
As the cerebral spinal fluid is made from small structures in the ventricles, each one is called a choroid plexus. The fluid then travels through the
ventricles. out of the 4th ventricle into the subarachnoid space. After it has circulated, it is absorbed into the venous system. Before entering the venous
system, the cerebral spinal fluid must pass through a delicate membrane that separates the fluid from blood in the nervous system. When there is blood in the
cerebral spinal fluid, this blood cannot pass through the barrier, and block the filtering system in the membrane to form an obstruction. Since the cerebral
spinal fluid cannot pass through from the nervous system it is forced to build up in the ventricles, which are cavities deep within the brain. If this condition
goes unchecked, the cerebral spinal fluid collecting in the ventricle(s) will eventually enlarge the ventricular system and leak into the surrounding brain matter.
This phenomenon produces progressive injury to the brain.
Symptoms
Typically, the symptoms of hydrocephalus appear slowly, over time. As the condition develops the symptoms become more noticeable and severe.
- Gait disturbance
- Slowing of mental functions (thought and actions)
- Memory loss
- Dementia
- Urinary incontinence
- Nausea/vomiting
- Headache
- Aggressive behavior (in some cases)
- Seizure (in some cases)
Treatment
The preferred treatment of hydrocephalus is called “shunting”, which is a surgical procedure that implants a tube leading from the ventricular cavity under the
skin to the abdominal cavity. This tube system contains a pressure-activated valve that opens when the pressure exceeds a predetermined level. Shunting is a
highly successful operation and is the agreed method for treating hydrocephalus. Before a patient undergoes surgery, intensive testing is done to determine that
shunting is safe for the patient.
Surgical Procedure:
The surgery itself involves drilling a small hole into the skull through which a tube is inserted into the ventricular cavities of the brain. The tube is then
passed under the skin into the abdominal cavity where the fluid is absorbed by the body. The shunt system is self-maintaining, but there is the possibility that
after a period of time one or more of the valves will need to be replaced. Improvement is usually seen soon after surgery.
Post-Operative Complications
After surgery, as with any operation, there are potential post-operative complications. Complications are rare in hydrocephalus patients, but the following
circumstances are potential problems.
Overdrainage can occur if the normal spinal fluid pressure is different from the valve settings in the shunt system, causing the shunt to siphon off
too much fluid. The sudden change of cerebral spinal fluid pressure can be very damaging. This also may lead to low-pressure syndrome where the decreased cerebral
spinal fluid pressure causes severe headache, vomiting, and pain at the base of the neck.
Subdural Hygromas are collections of spinal fluid that may develop within the first month after shunt placement. The hygromas may resolve but can enlarge,
indicating that the shunt valve pressure may need to be adjusted.
Underdrainage, like overdrainage, occurs when the shunt pressures do not match the patient’s cerebral spinal fluid pressure. The set valve pressure is not
able to offset the increased cerebral spinal fluid pressure due to hydrocephalus and therefore does not halt the progression of hydrocephalus.
Shunt Malfunction can cause symptoms of hydrocephalus to reappear. If the shunt is no longer performing because the valves have deteriorated over time they must be replaced.
Shunt Infection is always a risk, and if an infection develops after surgery the entire shunt system may need to be removed, the infection treated, and then the shunt system replaced.
Intracerebral Hemorrhage is bleeding within the brain and can develop from blood vessels tearing during the surgery with the placement of the shunt.
Seizure and Medical Conditions can also cause complications after surgery. Though rare, both are potential problems if they are present during the treatment of hydrocephalus.
Monitoring the progress of the patient is crucial after the placement of a shunt. Because there are potential complications, computed tomography testing should be done periodically to make sure that the
shunt is functioning properly. The physician will recommend which tests should be taken and the time intervals between testing. Because hydrocephalus is not eradicated, only controlled by the shunt system, the
patient must be monitored for shunt wear and tear and for the returning symptoms.
