A lesionectomy is an operation to remove a lesion -- a damaged or abnormally functioning area -- in the brain. Brain lesions include tumors, scars from a head injury or infection, abnormal blood vessels, and hematomas (a swollen area filled with blood).
A lesion seems to cause seizures in about 20% to 30% of people with epilepsy who do not improve after taking medication; it is not known for certain if the lesion itself triggers the seizures, or if the seizures result from irritation to the brain tissue surrounding the lesion. For this reason, surgery may also include the removal of a small rim of brain tissue around the lesion, called lesionectomy plus corticectomy.
Epilepsy is a brain disorder characterized by recurrent seizures -- episodes of abnormal electrical activity in almost any part of the brain. The symptoms of a seizure can mimic different types of human behavior, depending on which part of the brain is affected. Generally, the term epilepsy (or seizure disorder) refers to relatively stereotyped attacks of involuntary behavior. The exact symptoms and severity may vary, and the seizures may occur infrequently or in rapid succession.
Lesionectomy may be an option for people whose epilepsy is linked to a defined lesion and whose seizures are not controlled by medication. In addition, it must be possible to remove the lesion and surrounding brain tissue without causing damage to areas of the brain responsible for vital functions, such as movement, sensation, language, and memory. There also must be a reasonable chance that the person will benefit from surgery.
What Happens Before a Lesionectomy?
Candidates for lesionectomy undergo an extensive pre-surgery evaluation-including seizure monitoring, electroencephalography (EEG) and magnetic resonance imaging (MRI). These tests help to pinpoint the location of the lesion and confirm that the lesion is the source of the seizures. Another test to assess electrical activity in the brain is EEG-video monitoring, in which video cameras are used to record seizures while the EEG monitors the brain's activity. In some cases, invasive monitoring -- in which electrodes are placed inside the skull over a specific area of the brain -- is also used to further identify the tissue responsible for seizures.
What Happens During a Lesionectomy?
A lesionectomy requires exposing an area of 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 with 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 the brain tissue. Surgical microscopes are used to give the surgeon a magnified view of the lesion and surrounding brain tissue. The surgeon utilizes information gathered during pre-surgical brain imaging to help identify abnormal brain tissue and avoid areas of the brain responsible for vital functions.
In some cases, a portion of the surgery is performed while the patient is awake, using medication to keep the person relaxed and pain-free. This is done so that the patient can help the surgeon find and avoid vital areas of the brain. While the patient is awake, the doctor uses special probes to stimulate different areas of the brain. At the same time, the patient is asked to count, identify pictures, or perform other tasks. The surgeon can then identify the area of the brain associated with each task. After the brain tissue is removed, the dura and bone are fixed back into place, and the scalp is closed using stitches or staples.