Surgical Management of Epilepsy

The Medical College of Georgia (MCG) Epilepsy Surgery Program was established in1981 under the guidance of Dr. Herman F. Flanigin, who was one of Wilder Penfield's early residents at the Montreal Neurological Institute.

To date, we have performed over 1000 epilepsy craniotomies at MCG. Of these, 850 were performed on adults and 200 were performed on pediatric patients. Additionally, we have performed over 600 electrode implants, with 500 adult patients and 125 pediatric patients.

The Epilepsy Surgery program is comprised of a team of closely working professionals, including neurosurgeons, neurologists, neuropsychologists, nurses and other professionals experienced in the care and monitoring of patients with seizure disorders.

Surgical treatment of epilepsy is an effective therapy for certain types of epilepsies in both adults and children when seizures prove resistant to medical management.

The Epilepsy Surgery Program staff works closely with referring physicians throughout the course of a patient's evaluation and treatment to maximize continuity of care, particularly in the postoperative period.

Phase I (initial non-invasive) Evaluation

An initial one-to-two weeks in-hospital, pre-surgical evaluation includes a history, physical examination and neuropsychological testing to determine if there is evidence of localized brain dysfunction. Brain imaging, including special MRI techniques (PIC 1), are used to determine if a structural abnormality is causing the seizures. Interictal and Ictal SPECT scans are digitally merged and fused with MRI to identify areas of altered blood flow which may correlate with the site of seizure onset (PIC 2). In complex cases, magnetoencephalography (magnetic source imaging) is used to assist in the three-dimensional localization of the epileptogenic focus (PIC 3).

Patients undergo 24-hour video and EEG monitoring with scalp and sphenoidal electrodes to document the behavioral and physiological characteristics of seizures. Both interictal and ictal EEG recordings are used for localization. Medications are tapered during monitoring to increase the probability of recording seizures.

The initial evaluation also includes a bilateral carotid arteriogram and an intracarotid sodium amobarbital (Wada) test. The latter test determines which side of the brain controls language and memory function, and helps to ensure that surgery will not impair these processes.

Adults are evaluated in a self-contained, six-bed Adult Epilepsy Monitoring Unit with continuous video and 16-channel EEG monitoring for four patients and video and 64-channel EEG monitoring for two patients. Children are admitted to a two-bed pediatric unit which provides continuous video and 16-channel and 64-channel EEG monitoring.

Phase II (invasive) Evaluation

Patients whose seizures cannot be localized during the Phase I evaluation may require Phase II evaluation. During Phase II evaluation, patients undergo video and EEG monitoring with implanted intracranial electrodes in an attempt to localize more precisely the area of seizure onset. About 40 percent of surgical candidates undergoing Phase I evaluation will require Phase II investigation.

Types of intracranial electrodes include depth electrodes placed directly into brain structures (PIC 4), and subdural strip or grid electrodes placed over the cortical surface of the brain (PIC 5a & 5b). An advanced computer system allows MRI-directed stereotactic implantation of depth electrodes into specific brain structures (PIC 6). After implantation, patients again are monitored in the Epilepsy Monitoring Unit for one-to-two weeks.

Recommendation for surgery requires the recording of multiple seizures with localized seizure onset.

Surgery

If pre-surgical evaluation suggests that surgery may be beneficial, patients may undergo one of the following procedures:

Anterior temporal lobectomy - removal of the anterior temporal lobe including the medial temporal structures (DRAW 1).

Extratemporal resection - removal of epileptogenic cerebral cortex outside the anterior temporal lobe (PIC 7).

Functional hemispherectomy - removal of the majority of one cerebral hemisphere and functional disconnection of the remainder of the hemisphere in patients with severe unilateral damage and intractable epilepsy (PIC 8a & 8b).

Hemispherotomy - This is a significant modification of hemispherectomy which primarily involves disconnecting the damaged, epileptogenic hemisphere rather than removing tissue (DRAW 2a & 2b). It is a much shorter operation than hemispherectomy, and is ideally suited for patients with significant atrophy of the damaged hemisphere (which make up about 60% of our candidiates for hemsipherectomy

Corpus Callosotomy - sectioning of the corpus callosum to disconnect the two hemispheres and prevent the spread of seizures from one hemisphere to the other (PIC 9). This remains an effective operation for patients with generalized tonic clonic seizures or drop attacks whose seizures are poorly localized with EEG. (DRAW 3a-d)

Multiple subpial transection - transection of the cortex without removal when the epileptogenic zone is in a functionally important area, e.g. frontal and parietotemporal language cortex.

Vagal Nerve Stimulation - Involves implantation of a stimulating electrode around the left vagal nerve and attaching it to a pulse generator which is implanted under the skin just below the collar bone. The pulse generator is programmed with a specific on/off cycle and frequency of stimulation. Stimulation amplitude is increased incrementally to improve seizure frequency. This operation is typically offered to patients with complex partial epilepsy poorly localized with EEG.

Gamma Knife - This non-invasive technology is sometimes used to treat epilepsy associated with small structural lesions. In selected cases results are comparable to open surgery.

Surgical Results

Surgical success depends on the type of surgery, but most patients are substantially improved.

Approximately 70 percent of patients who have an anterior temporal lobectomy are seizure-free one year following surgery, and 90 percent show marked improvement.

Fifty percent are seizure-free one year following extratemporal resections, and 75 to 80 percent are significantly improved.
Between 50 and 70 percent of patients who have a corpus callostomy have shown greater than 90 percent improvement for certain types of seizures.

Seventy percent of patients who undergo hemispherectomy or hemispherotomy are seizure-free postoperatively, and nearly all are improved.

Preliminary data suggest that multiple subpial transection may effectively decrease seizures without causing a neurological deficit.
Approximately 50% of patients undergoing vagal nerve stimulation will show a 50% improvement in seizure frequency.

Postoperative Care

Surgery requires a variable hospital stay. Patients return to MCG for initial follow-up after their release from the hospital. They then return to their referring physician for long-term care.

The Epilepsy Surgery Team

Joseph R. Smith, M.D., F.A.C.S., Professor, Neurosurgery,
Director of Epilepsy Surgery

Mark R. Lee, M.D., Ph.D., Professor and Chair, Neurosurgery,
Director, Pediatric Epilepsy Surgery 

Yong D. Park, M.D., Professor, Neurology,
Director, Pediatric Epilepsy Program

Anthony M. Murro, M.D., Professor, Neurology

Gregory P. Lee, Ph.D., Professor, Neurology

Pamela Culberson-Brown, Nurse Clinician, Pediatric Epilepsy


The program staff welcomes any inquiries or referrals and can be reached through the Adult Epilepsy office at (706) 721-3325, the Pediatric Epilepsy Office at (706) 721-3371 or through MCG Physicians Direct at 1-800-733-1828.
 

Questions and Comments to Bill Hamilton 

 
 January 12, 2007

Department of Neurosurgery  |  Medical College of Georgia