Abstracts

Rationale: Cortical stimulation often is used to help localize motor, sensory, language, and other functional areas in patients who have had subdural electrodes implanted prior to resections for seizure control. Brief pulses of electrical stimulation (BPS; Neurology 53:2073-2081, 1999) can be effective in ending afterdischarges (ADs), when they occur during cortical stimulation. However, it is possible that they also could initiate, alter, or prolong ADs. Methods: We reviewed EEG recordings of patients with implanted subdural electrodes and who were undergoing stimulation testing to localize cortical areas controlling motor, sensory, or language functions. We reviewed BPS events when they occurred, and reviewed the effects of BPS on ADs. Results: BPS could modify the appearance of ADs without stopping them. These AD modifications show as abrupt switching between distinct patterns. Also, BPS could reinitiate ADs that had stopped. Conclusions: BPS can terminate ADs, but also can modify ADs morphology or result in their recurrence. These possibilities should be considered when using BPS to terminate ADs.