context: 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. 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. 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. 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. After a lesionectomy, the patient generally stays in an intensive care unit for 24 to 48 hours after surgery and then stays in a regular hospital room for three to four days. Most people who have a lesionectomy 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 antiseizure medications. Once seizure control is established, medications may be reduced or eliminated. Lesionectomy results are excellent in patients whose seizures are clearly associated with a defined lesion. Side effects of a lesionectomy vary depending on the location and extent of the lesion and the tissue removed. The following side effects may occur after surgery, although they generally go away on their own: Scalp numbness Nausea Feeling tired or depressed Headaches Difficulty speaking, remembering, or finding words Weakness, paralysis Change in personality, memory loss The risks associated with lesionectomy include: Risks associated with surgery, including infection, bleeding, and an allergic reaction to anesthesia Failure to relieve seizures Swelling in the brain Damage to healthy brain tissue