We present two cases of epilepsy with negative scalp EEG and challenging semiologies, the workup undertaken to identify them as cases of insular epilepsy, and subsequent surgical treatment.

Patient 1 is a 53-year-old man who developed daily seizures as a teenager. Semiology was described as facial tingling and hyperkinetic movements (clapping, slapping his head), frequently out of sleep, and he had been diagnosed with non-epileptic spells for years. Ictal scalp EEG showed diffuse slowing and interictal EEG was normal. Brain MRI, ictal SPECT, neuropsychological testing, and magnetoencephalography were non-localizing. Stereotactic EEG (SEEG) identified seizure onset in the right anterior insula, reproducible with cortical stimulation. He underwent right anterior insular resection and, over a year post-op, remains seizure free on medications.

Patient 2 is a 41-year-old man with daily seizures starting at age 4. Semiology was described as right eye blinking, left arm freezing, sensation of left foot pressure, and hyperkinetic movements (cheek puffing, crying, sliding up and down in bed). Ictal and interictal scalp EEG showed midline and bifrontal slowing. Brain MRI, ictal SPECT, and neuropsychological testing were non-localizing. SEEG identified seizure onset from the right insula and frontal operculum, reproducible with cortical stimulation. He underwent resection and is now four years post-op. Seizure frequency has improved to once every several months on medications.

SEEG was instrumental in localizing the epileptogenic zone in our cases of insular epilepsy. In both patients, SEEG ictal evolution was only seen over the insula, mesial frontal cortex, and anterior cingulate gyrus, and therefore was not detected on scalp EEG. Resective surgery has subsequently improved quality of life for both patients. These cases highlight the importance of recognizing the unusual semiology of insular epilepsy and the workup needed to identify it.