Hippocampal volumetry and T2 relaxometry were performed on 84 consecutive patients (adolescents and adults) with partial epilepsy submitted to antiepileptic drug (AED) withdrawal after at least 2 years of seizure control, in a study at State University of Campinas-UNICAMP, Brazil. Ages ranged from 15 to 76 years (mean, 30 years), and follow-up varied from 5.6 to 11.2 years (mean, 8 years). Hippocampal atrophy was present in 39 (46%) patients; bilateral in 13 and unilateral in 26. Age at time of scanning, age at seizure onset, and duration of epilepsy were similar in groups with and without HA. Seizure recurrence was more frequent in patients with HA (29/39, 74%) than in those with normal hippocampal volumes (21/45, 47%). Abnormal T2 relaxation times were found in patients with more pronounced HA, and with seizure recurrence. [1]

COMMENT. The probability of seizure remission for 5 years after AED withdrawal is 62% in patients without HA, 28% in those with HA, 62% with normal T2 signal, and 23% with abnormal T2 signal. Hippocampal atrophy and hyperintense T2-weighted signal are the MRI abnormalities commonly found in patients with mesial temporal lobe epilepsy. MRI is of value in predicting outcome following AED withdrawal, particularly in patients with HA.

In an editorial, Berg AT and Engel J Jr [2] point out that the study does not clarify whether the effects of HA are independent of age at onset, and history of febrile seizures. The relation between HA and a diagnosis of mesial temporal lobe epilepsy was not determined in this series of patients.