Epilepsy

Surgery

SISCOM technology can pinpoint seizure focal points, which show up as green spots in the first two scans and bright yellow in the last scan.

Enlarge

Although many people can control their seizures effectively with medication, about 30 percent don't benefit from medication because of a lack of seizure control or side effects of the medication, or both. For many of these people, surgery is the best option for relief.

During a typical epilepsy surgery, surgeons remove the portion of the brain that is causing the seizures. While the procedure is relatively safe and quite effective, finding the exact location of the electrical misfiring in the brain that causes seizures can be extremely challenging.

Historically, the tests used to look for epilepsy "hot spots" often have been inconclusive or vague. When this occurs, one option in severe cases has been to remove most or all of one side of the brain to ensure removal of all the seizure hot spots. This radical surgery can leave serious mental and physical disabilities. In other cases, when physicians have been unable to pinpoint the hot spot, the patients have not been able to have surgery.

SISCOM and Epilepsy Surgery

An imaging technique developed at Mayo Clinic in the late 1990s has given patients a better chance of having successful surgery outcomes. SISCOM (Subtraction Ictal SPECT Co-registered to MRI) uses proven imaging technology with computer software to pinpoint seizure hot spots.

Traditionally, physicians have compared two SPECT (single photon emission computed tomography) scans of the brain: one taken during a seizure and one while seizure-free. The goal is to compare the two scans and find out where seizures are originating.

Differences between the two SPECT scans are very difficult to detect with the human eye. In response, a team of Mayo Clinic physicians and scientists developed a computer software program that electronically subtracts one image from the other, leaving a clear picture of the seizure hot spot. Next, the subtracted image is superimposed onto an MRI scan of the patient's brain so that neurosurgeons can verify the hot spot's anatomic location and remove it safely.

A published study showed that SISCOM correctly located seizure hot spots in more than 88 percent of cases, compared with only 39 percent using the older technique.

SISCOM can be used for patients of all ages, and has allowed some operations that may not have been possible before.