TEMPORAL ICTAL ELECTROENCEPHALOGRAPHIC FREQUENCY CORRELATES WITH HIPPOCAMPAL ATROPHY AND SCLEROSIS

We studied 328 complex partial seizures (CPS) in 63 consecutive patien ts with temporal lobe epilepsy who underwent scalp electroencephalogra phy/video monitoring, magnetic resonance imaging (MRI), and surgery. T he initial ictal discharge (IID), defined as the first sustained elect rical seizure pattern localized to the surgical site, was determined. If the IID was rhythmic waves, the median frequency was measured. To d etermine if IID frequency correlates with hippocampal atrophy (HA) or sclerosis (HS), hippocampal volume ratios (HVRs) were measured (n = 52 ) or assessed visually (n = 11) on MRI, and mesial temporal histopatho logy specimens (n = 22) were graded for HS. Sixteen patients (25%) had no or mild HA (HVR = 0.78-1.02), and 47 patients (75%) had moderate-t o-marked unilateral (HVR = 0.33-0.76), or bilateral, HA. Theta frequen cy IIDs were significantly more commonly associated with moderate-to-m arked HA than were delta IIDs. Theta frequency IIDs occurred in 19% of patients with mild or no HA, and 79% of patients with moderate-to-mar ked HA; delta IIDs occurred in 63% of patients with little to no HA, a nd 13% of those with moderate-to-marked HA. In addition, the median II D frequency inversely correlated with HVR and directly correlated with HS severity. In conclusion, faster frequency rhythmic IIDs during tem poral lobe CPS correlate with greater degrees of ipsilateral HA on MRI , and higher grades of HS.