What Is a Functional Hemispherectomy?
The largest part of the brain,
the cerebrum, can be divided down the middle lengthwise into two
halves, called hemispheres. A deep groove splits the left and right
hemispheres, which communicate through a thick band of nerve fibers
called the corpus callosum. Each hemisphere is further divided into four
paired sections, called lobes -- the frontal, parietal, occipital, and
temporal lobes.
The two different sides or
hemispheres are responsible for different types of activities. The left
side of the brain controls the right side of the body and vice versa.
For most people, the ability to speak and understand the spoken word is a
function of the left side of the brain. A functional hemispherectomy is
a procedure in which portions of one hemisphere -- which are causing
the seizures -- are removed, and the corpus callosum, which connects
the two sides of the brain, is cut. This disconnects communication
between the two hemispheres, preventing the spread of electrical
seizures from one side of the brain to the other. As a result, the
person usually has a marked reduction in physical seizures.
Switching Epilepsy Medications
Fifty
percent of all patients with newly diagnosed epilepsy will become
seizure-free with the first epilepsy drug they try. For the rest, it's
try, try again: switching epilepsy medications, adjusting to side
effects, and waiting to make sure the new drug works. Others find their
seizures are controlled, but they can't tolerate the medication's side
effects and need to switch drugs.
Before you ask your doctor if your medication should be switched, make
sure you are taking your current medication...
Who Is a Candidate for a Functional Hemispherectomy?
This procedure generally is used only for people with epilepsy who do not experience improvement in their condition after taking many different medications
and who have severe, uncontrollable seizures. This type of epilepsy is
more likely to be seen in young children who have an underlying disease,
such as Rasmussen's encephalitis or Sturge-Weber syndrome, that has damaged the hemisphere.
What Happens Before a Functional Hemispherectomy?
Candidates for functional hemispherectomy undergo an extensive pre-surgery evaluation -- including seizure monitoring, electroencephalography (EEG), and magnetic resonance imaging
(MRI). These tests help the doctor identify the damaged parts of the
brain and confirm that it is the source of the seizures. An intracarotid
amobarbital test, also called a WADA test, is done to determine which
hemisphere is dominant for critical functions such as speech and memory.
During this test, each hemisphere is alternately injected with a
medication to put it to sleep. While one side is asleep, the awake side is tested for memory, speech, and ability to understand speech.
What Happens During a Functional Hemispherectomy?
A functional hemispherectomy requires exposing the brain using a procedure called a craniotomy. "Crani" refers to the skull and "otomy"
means "to cut into." After the patient is put to sleep (general
anesthesia), the surgeon makes an incision (cut) in the scalp, removes a
piece of bone and pulls back a section of the dura, the tough membrane
that covers the brain. This creates a "window" in which the surgeon
inserts special instruments for removing brain tissue. Surgical
microscopes are utilized to give the surgeon a magnified view of the
brain structures. During the procedure, the surgeon removes portions of
the affected hemisphere, often taking all of the temporal lobe but
leaving the frontal and parietal lobes. The surgeon also gently
separates the hemispheres to access and cut the corpus callosum. After
the tissue is removed, the dura and bone are fixed back into place, and
the scalp is closed using stitches or staples.
What Happens After a Functional Hemispherectomy?
The
patient generally stays in an intensive care unit for 24 to 48 hours
and then stays in a regular hospital room for three to four days. Most
people who have a functional hemispherectomy will be able to return to
their normal activities, including work or school in six to eight weeks
after surgery. Most patients will need to continue taking anti-seizure
medication, although some may eventually be able to stop taking
medication or have their dosages reduced.
How Effective Is Functional Hemispherectomy?
About
85% of people who have a functional hemispherectomy will experience
significant improvement in their seizures, and about 60% will become
seizure-free. In many cases, especially in children, the remaining side
of the brain takes over the tasks that were controlled by the section
that was removed. This often improves a child's functioning and quality
of life, as well as reduces or eliminates the seizures.
What Are the Side Effects of a Functional Hemispherectomy?
The following symptoms may occur after a functional hemispherectomy, although they generally go away over time and with therapy:
- Scalp numbness.
- Nausea.
- Muscle weakness on the affected side of the body.
- Puffy eyes.
- Feeling tired or depressed.
- Difficulty speaking, remembering, or finding words.
- Headaches.
What Risks Are Associated With a Functional Hemispherectomy?
The risks associated with a functional hemispherectomy include:
- Risks associated with surgery, including infection, bleeding, and an allergic reaction to anesthesia.
- Loss of movement or sensation on the opposite side of the body.
- Swelling in the brain.
- Delayed development.
- Loss of peripheral (side) vision.
- Failure to control seizures.
No comments:
Post a Comment