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Functional mapping of the insular cortex: clinical implication in temporal lobe epilepsy
K Ostrowsky1, J Isnard, P Ryvlin
1Functional Neurology and Epileptology Department, Hôpital Neurologique, Lyon, France.
Epilepsia
|June 7, 2000
Summary
Electrical stimulation of the insular cortex in epilepsy patients revealed distinct topographic organization. Anterior insula stimulation elicited visceral responses, while posterior stimulation evoked somatosensory responses, aiding in understanding seizure spread.
Area of Science:
- Neuroscience
- Epileptology
- Clinical Neurophysiology
Background:
- Drug-resistant partial epilepsy often involves complex seizure propagation patterns.
- The insular cortex plays a role in various functions, including visceral and somatosensory processing.
- Understanding insular cortex involvement is crucial for localizing seizure origins and spread.
Purpose of the Study:
- To investigate the functional organization of the insular cortex through intracortical electrical stimulation.
- To determine the topographic specificity of responses evoked by stimulating different insular cortex regions.
- To correlate insular cortex stimulation responses with seizure propagation patterns in epilepsy.
Main Methods:
- Performed 75 intracortical electrical stimulations of the insular cortex in 14 patients undergoing stereo-electroencephalography (SEEG) for drug-resistant partial epilepsy.
- Used stereotactically implanted transopercular electrodes to reach the insular cortex (anterior/posterior regions).
- Applied low (1 Hz) and high-frequency (50 Hz) electrical stimulation, analyzing symptoms evoked in the absence of afterdischarges.
Main Results:
- Clinical responses were evoked in 10 of 14 patients (20 of 27 sites), demonstrating clear topographic specificity within the insular cortex.
- Anterior insular stimulation evoked viscerosensitive and visceromotor responses, similar to temporomesial stimulation.
- Posterior insular stimulation evoked somatosensory sensations, similar to opercular cortex stimulation.
Conclusions:
- The topographic organization suggests distinct networks: an anterior visceral network connected to temporomesial structures and a posterior somatosensory network connected to the opercular cortex.
- Ictal symptoms from insular cortex involvement may be challenging to differentiate from those of temporomesial or opercular origin.
- Electrical stimulation mapping provides insights into the functional segregation and connectivity of the insular cortex in epilepsy.