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Localization of subclinical ictal activity by functional magnetic resonance imaging: correlation with invasive
J A Detre1, J I Sirven, D C Alsop
1Department of Neurology, University of Pennsylvania, Philadelphia 19104, USA.
Abstract:
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 with frequent partial motor seizures involving his right lower face that spread to produce speech arrest and occasionally right arm jerking. Consciousness was never impaired during these events. A multislice echoplanar technique was used to acquire 16 contiguous axial slices every 4 seconds for 11 minutes. Although no overt seizures were observed or reported by the patient during the scanning, a time series analysis of the functional data revealed focal signal-intensity changes in the posterior left frontal lobe, which correlated well both in duration and spatial localization with ictal activity subsequently recorded by invasive 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 results illustrate the potential of functional MRI for localizing seizure foci with high spatial and temporal resolution. Such studies can be readily combined with high-resolution anatomical imaging, task-activation studies, and other magnetic resonance techniques.
Insights
Functional MRI (fMRI) precisely located epilepsy seizure foci in the brain. This advanced imaging technique proved more accurate than electroencephalography for guiding epilepsy surgery.
Area of Science:
- Neuroimaging
- Epileptology
- Functional Magnetic Resonance Imaging
Background:
- Focal epilepsy diagnosis often relies on correlating clinical symptoms with neurophysiological data.
- Accurate localization of seizure onset zones is critical for successful surgical intervention.
Observation:
- Functional magnetic resonance imaging (fMRI) was employed using susceptibility-based contrast to monitor cerebral blood flow and metabolism.
- A patient with focal epilepsy experiencing partial motor seizures underwent fMRI scanning.
- Despite no observed seizures during scanning, time-series analysis revealed focal signal changes in the posterior left frontal lobe.
Findings:
- fMRI detected focal signal-intensity changes that correlated spatially and temporally with ictal activity identified by invasive electrophysiological monitoring.
- The spatial accuracy of fMRI in localizing the seizure focus surpassed that of subdural grid electroencephalography.
- fMRI successfully predicted the site of successful epilepsy surgery.
Implications:
- Functional MRI demonstrates significant potential for high-resolution spatial and temporal localization of seizure foci.
- fMRI can be integrated with anatomical imaging and other MRI techniques for comprehensive epilepsy evaluation.
- These findings support the use of fMRI as a valuable tool in the pre-surgical assessment of epilepsy.