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Absolute spike frequency predicts surgical outcome in TLE with unilateral hippocampal atrophy

From the 2nd Neurological Department, General Hospital Hietzing with Neurological Center Rosenhuegel, Vienna; and the Department of Neuology, Medical University of Vienna, Austria.

Address correspondence and reprint requests to Dr. Christoph Baumgartner, 2nd Neurological Department, General Hospital Hietzing with Neurological Center Rosenhuegel, Riedelgasse 5, A-1130 Vienna, Austria christoph.baumgartner{at}wienkav.at

Objective: To assess the prognostic implications of both the absolute spike frequency over the affected temporal lobe and the relative spike distribution between the two temporal lobes (i.e., uni- vs bitemporal spike distribution) for postoperative seizure control in a series of consecutive patients with medically refractory mesial temporal lobe epilepsy (MTLE) and MRI evidence of unilateral hippocampal atrophy (HA).

Methods: In this study we included 55 patients (26 women; 29 men) with medically refractory MTLE and unilateral HA on high resolution MRI who underwent a comprehensive noninvasive presurgical evaluation including prolonged video-EEG monitoring. Patients were classified both according to absolute interictal spike frequency and to relative spike distribution between the two temporal lobes as follows: first, we distinguished between patients with frequent spikes (60 spikes/hour over the affected temporal lobe) and patients with nonfrequent spikes (<60 spikes/hour over the affected temporal lobe). Second, we categorized patients in a unitemporal group (90% of spikes over the affected temporal lobe) and a bitemporal group (<90% of spikes over the affected temporal lobe). In all patients first-time epilepsy surgery was performed with a minimum postoperative follow-up of 1 year.

Results: One year following surgery we found that only 4 of 14 patients (28.6%) in the frequent spikes group remained completely seizure free since surgery compared to 33 of 41 patients (80.5%) in the nonfrequent spikes group (p = 0.001). Relative spike distribution did not show any significant implication for postoperative outcome.

Conclusions: This study identified absolute preoperative spike frequency as a strong predictor for surgical outcome, while relative spike distribution had no significant influence on postoperative seizure control.

Abbreviations: AMTR = anterior medial temporal resection; FDG = fluorodeoxyglucose; GTCs = generalized tonic-clonic seizures; HA = hippocampal atrophy; IED = interictal epileptiform discharges; MTLE = mesial temporal lobe epilepsy; sAHE = selective amygdalohippocampectomy.

Editorial, page 392

e-Pub ahead of print on July 9, 2008, at www.neurology.org.

Disclosure: The authors report no disclosures.

Received July 14, 2007. Accepted in final form January 7, 2008.