Absolute spike frequency and etiology predict the surgical outcome in epilepsy due to amygdala lesions

To identify surgical prognostic factors for temporal lobe epilepsy (TLE) due to amygdala lesions.

We included 42 patients (mean age: 31.4 ± 11) who underwent presurgical evaluation including long-term video-EEG and in whom the high-resolution MRI showed amygdala lesions without hippocampal abnormalities. All patients had apical temporal lobe resection without hippocampectomy. We distinguished patients with frequent spikes (spike frequency ≥ 60/h) and with non-frequent spikes (< 60 spikes/h).

At the 2-year postoperative evaluation, 30 patients (71%) were seizure-free. The presence of infrequent spikes (p = 0.013), tumor on the MRI (p = 0.027), and no epilepsy history in the family (p = 0.027) were independently associated with 2-year seizure-free outcome. Of 33 patients with infrequent spikes, 79% became seizure-free, while of 9 patients with frequent spikes only 4 had a favorable surgical outcome (44%).

In TLE patients due to amygdala lesions, high spike frequency and family history of epilepsy predicted an unfavorable, while tumoral etiology a favorable outcome after apical temporal lobe resection without hippocampectomy. Seventy-one percent of patients with amygdalar epilepsy who underwent this novel type of epilepsy surgery became seizure-free. This is comparable with results of "classical" anterior temporal lobe resections where hippocampus is NOT spared. Moreover, the surgical outcome may be predictable.