Abstracts

RATIONALE:_Focal MRI abnormalities in the anterior temporal pole (ATP), ie. signal changes, loss of gray-white differentiation and atrophy, have recently been recognized to be common in medically refractory temporal lobe epilepsy (TLE) with hippocampal sclerosis (HS). However, these changes are also seen in some TLE patients without HS. The significance of these findings, and whether they represent an independent potentially epileptogenic abnormality, is uncertain. The aim of this study was to determine whether ATP changes without HS represents a different syndrome or are part of the mesial temporal sclerosis (MTS) spectrum. METHODS:_The clinical, EEG, FDG-PET and surgical outcome results of 15 consecutive TLE patients with unilateral ATP changes without HS (ie. normal hippocampal volumes and T2 signal) were compared with 12 consecutive HS patients studied in a similar manner. The FDG-PET scans were reviewed by a blinded reviewer who attempted to classify the patients into ATP or HS groups on the basis of the hypoperfusion patterns. RESULTS:_The HS patients more frequently had a history of a remote symptomatic neurological insult (58% vs. 13%, p<0.05) and it occurred at an earlier age (median 2 vs. 18.5 years, p<0.05). A history of febrile convulsions was only seen in the HS group (42%). The ictal EEG pattern in the ATL group more frequently showed a focal delta rhythm (58% vs 10%, p<0.05), compared with a focal theta rhythm in the HS group (60% vs 25%, p=0.20). The incidence and localization of the interictal EEG epileptiform abnormalities did not differ between the groups. The FDG-PET scans showed unilateral focal hypometabolism in 100% of both groups, but its pattern did not allow distinction between the groups. Epilepsy surgery has been performed in 9 patients from both groups with at least 9 months follow-up. There was no significant difference in outcome between the groups (77% vs. 89% seizure free, p<0.05) despite the ATP patients having a hippocampal sparing procedure. CONCLUSIONS:_The clinical, EEG and surgical outcome results suggest that TLE with ATP changes without HS may be a distinct syndrome, rather than merely part of the spectrum of MTS.