Non-invasively recorded regional polyspikes are suggestive of cortical dysplasia as aetiology of Focal Epilepsies

Purpose: To evaluate the relative frequency of regional polyspikes in focal epilepsies secondary to cortical dysplasia.

Method: We performed a data search for the term „regional polyspikes“ in the data base of our Epilepsy Monitoring Unit. Patients with generalized epilepsies and Lennox-Gastaut syndrome were excluded. Regional interictal epileptiform discharges were recorded in 514 patients with non-invasive EEG.

Results: We identified 29 patients with regional polyspikes and focal epilepsies. Another 485 patient showed regional epileptiform discharges other than polyspikes. The polyspikes were significantly more frequently localized to the extratemporal (76%; n=22) than temporal (24%; n=7) regions (p<0.01). In contrast, regional epileptiform discharges other than polyspikes were significantly more frequently localized to the temporal lobes (71%; n=324) than extratemporally (29%; n=161)(p<0.01). The etiology of the epilepsy was significantly more frequently cortical dysplasia in the group of patients with regional polyspikes (31%, 9 of 29 patients) than in the other patients with regional epileptiform discharges (5,1%, 25 of 485 patients) (p<0.01).

Conclusion: Non-invasively recorded regional polyspikes point to cortical dysplasias as etiology of predominantly extratemporal epilepsies.