LOCALIZATION OF SUBCLINICAL ICTAL ACTIVITY BY FUNCTIONAL MAGNETIC-RESONANCE-IMAGING - CORRELATION WITH INVASIVE MONITORING

Functional magnetic resonance imaging (fMRI) with susceptibility-based contrast was used to detect focal changes in cerebral blood flow and metabolism in a patient with focal epilepsy. The patient presented wit h frequent partial motor seizures involving his right lower face that spread to produce speech arrest and occasionally right arm jerking. Co nsciousness was never impaired during these events. A multislice echop lanar technique was used to acquire 16 contiguous axial slices every 4 seconds for 11 minutes. Although no overt seizures were observed or r eported by the patient during the scanning, a time series analysis of the functional data revealed focal signal-intensity changes in the pos terior left frontal lobe, which correlated well both in duration and s patial localization with ictal activity subsequently recorded by invas ive electrophysiological monitoring. The spatial localization of fMRI was more accurate than electroencephalography recorded from a subdural grid in predicting the site of successful surgical therapy. These res ults illustrate the potential of functional MRI for localizing seizure foci with high spatial and temporal resolution. Such studies can be r eadily combined with high-resolution anatomical imaging, task-activati on studies, and other magnetic resonance techniques.