Intraoperative Optical Mapping of Human Neocortical Epilepsy in the Treatment of Partial Onset Seizures

Theodore H. Schwartz, M.D.

Weill Cornell Medical College / New York Presbyterian Hospital, New York, NY

Grant Program:

David Mahoney Neuroimaging Program

Funded in:

November 2001, for 3 years

Funding Amount:

$100,000

Abstract

Intraoperative Optical Mapping of Human Neocortical Epilepsy in the

Surgical removal of the epileptic focus is currently the most effective method for eliminating partial onset neocortical seizures. Critical to the success of epilepsy surgery is the ability to rapidly and accurately identify the topographical limits of the epileptic focus. Chronic and acute electrical recordings from the surface of the brain have been the “gold standard” in human cortical mapping. These techniques have several inherent limitations based on grid placement, inter-electrode distances and volume conduction. Since the epileptogenic pool of neurons responsible for non-lesional neocortical epilepsy is often widespread and may fluctuate over time, accurate localization is essential. Surgery guided by electrical recordings successfully eliminates seizures in less than 50% of patients.

An alternative technique to electrical recording for monitoring neuronal activity is optical recording of changes in reflectance of light associated with neuronal activity. The advantage of optical recording is that a large area of cortex can be sampled simultaneously with extremely high spatial-resolution. Optical mapping has been used extensively in the laboratory but infrequently in humans based on technical limitations. The purpose of this proposal is to build an apparatus for intrinsic signal imaging that is specifically designed for intraoperative human brain mapping. We will systematically investigate the optimal technique for intraoperative epilepsy mapping to explore the dynamic spatio-temporal limits of the epileptic focus associated with lesional and non-lesional neocortical epilepsy. The ultimate goal is to determine whether surgical resections based on optical epilepsy maps can improve surgical results thereby eliminating seizures, medications, and side effects in greater number of appropriately selected patients.

Investigator Biographies

Theodore H. Schwartz, M.D.

Department of Neurological Surgery, Weill Cornell Medical College / New York Presbyterian Hospital

Hypothesis

Hypothesis:
Intraoperative optical recording of intrinsic signals is a more accurate technique for mapping human neocortical epilepsy than current electrophysiological methods, which have inherent limitations in spatial localization. Surgical resections based on this novel optical mapping technique will lead to improved outcome in the treatment of human epilepsy.

Goals:
1. To optimize the intraoperative application of intrinsic signal imaging.
2. To optically map human neocortical epilepsy.

Methods:
Patients undergoing resective surgery for medically intractable neocortical epilepsy will undergo electrocorticography to localize interictal and ictal spike zones. These regions will be imaged with a custom designed camera holder and cortical stabilization equipment using a CCD camera while simultaneously recording the ECoG.

Findings:
Ictal onsets can be localized with intrinsic signal imaging of blood flow and oxygenation changes. These focal hemodynamic signals may precede the onset of the seizure and be useful at predicting seizure onset.

Selected Publications

Schwartz T.H. and Bonhoeffer T. In vivo optical mapping of epileptic foci and surround inhibition in ferret cerebral cortex . Nat Med. 2001 Sep;7(9):1063-7 .