What is hydrocephalus and how is it treated?

DEAR DOCTOR K:

My father had been showing signs of dementia for a few months. We thought it was Alzheimer’s disease, but it turned out to be hydrocephalus. What is this, and how is it treated? Does the condition cause permanent brain damage?

DEAR READER:

Hydrocephalus is a condition in which extra cerebrospinal fluid collects inside the brain. (Another name for it is “water on the brain.”) Cerebrospinal fluid acts as a cushion for the brain and spinal cord. It also supplies nutrients and removes waste products. (I’ve put an illustration of a brain affected by hydrodcephalus, below.)

Cerebrospinal fluid flows in a space between the outer layer of the brain and the skull. It also is found in small “lakes” inside the brain called ventricles, and in a space around the spinal cord. It is the fluid surrounding the spinal cord from which doctors take a sample when they perform a “spinal tap.” The fluid is made in the brain. At about the same rate as it is made, some of the fluid leaves the brain and enters the blood to travel elsewhere in the body.

AZ_d0247-1Hydrocephalus is a condition in which there is extra cerebrospinal fluid around the brain and spinal cord.

In most people, the amount of fluid inside the ventricles remains mostly constant during adult life. In people with hydrocephalus, the ventricles (and the amount of fluid in them) expands.

Your father most likely experienced a type of hydrocephalus known as normal-pressure hydrocephalus (NPH). NPH occurs in a small number of older adults. It can result from head trauma, bleeding in the brain or inflammation of the membrane covering the brain. In about half of cases, doctors never identify what caused it. Something goes wrong with the system that moves fluid out of the brain and into the blood.

People with NPH can develop dementia; they may also lose bladder control. They walk with difficulty: short steps, feet placed wide apart and toes pointing outward for balance. Because of the problems with walking and balance, people with NPH tend to fall. Therefore, they are at increased risk for fracturing their hips and other bones.

To make a diagnosis, a doctor will use computed tomography (CT) or magnetic resonance imaging (MRI) to look for enlarged ventricles in the brain. Next, the doctor will remove a large amount of this fluid with a spinal tap. If NPH is causing the problems, removing the fluid will lead to a temporary, but dramatic, improvement in symptoms.

To treat the condition permanently, a surgeon will implant a tube (called a shunt) that continuously drains excess fluid from the brain. The shunt is inserted into a ventricle through a hole in the skull. It is tunneled under the skin and carries the fluid into another area of the body, where it can be absorbed.

It is possible to largely reverse the effects of NPH, particularly if the problem is diagnosed and treated early. If your father’s CT or MRI scan shows little or no loss of brain tissue, or of impaired blood flow in the brain, those are encouraging signs. Hopefully, he will have a good response to the treatment.