POSTSURGICAL OUTCOME OF FRONTAL LOBE EPILEPSY. AN UNEXPECTED FINDING [P07.114]

Manuel Toledo, Antoaneta Balabanov, Richard Byrne, Michael Smith, Donna Bergen, Chicago, IL; Marvin Rossi, Oak Park, IL; Thomas Hoeppner, Michael Stein, Travis Stoub, Andres Kanner, Chicago, IL

Patients who undergo surgical resection for frontal lobe epilepsy (FLE) often have good outcomes when an identifiable lesion is present. In recent case series, approximately 50% of patients have been seizure free after 1 to 5 years.^1,2 In some studies, outcomes have been worse for patients with nonlesional FLE.^1,3 Other potential factors that are important in the long-term outcomes of these patients are poorly understood. One recent study found that patients who were seizure free at 2 years were likely to remain seizure free when followed for up to 10 years.¹ In this poster, the investigators examined potential predictors of clinical outcomes in patients undergoing FLE surgery, with particular attention to the earliest postsurgical outcome that was predictive of long-term success. 

The investigators retrospectively assessed 26 consecutive patients (14 males) who underwent resective frontal lobe surgery for medically refractory FLE. The mean age at seizure onset was 12.3 years and the mean age at surgery was 29.3 years. Patients were followed up for a minimum of 1 year, and the mean duration of follow-up was 6.6 years. Seizure outcomes were assessed for up to 5 years after surgery, and were rated as Class 1 (seizure free with or without auras); Class 2 (reduction of complex partial seizures of at least 75% from baseline, and no secondarily generalized tonic-clonic seizures [GTC]); Class 3 (reduction of seizures from baseline by at least 75%, with GTC); and Class 4 (reduction of seizure frequency of less than 75% and/or GTC). Surgical outcome was then categorized as favorable (Class 1 or Class 2) or unfavorable (Class 3 or Class 4). Surgical resection was performed on the nondominant hemisphere in 18 patients (60%), 12 patients (46%) had simple partial seizures, 22 patients (84%) had complex partial and secondarily generalized seizures, and 12 patients (46%) had nonlesional FLE. Surgical resection alone was performed in 22 patients, and 4 patients underwent resection and multiple subpial transection.

After 1 year, 69% of the patients exhibited a favorable outcome (Class I or II): 38% were Class 1, 31% Class 2, 8% Class 3, and 23% Class 4. After 4 years, 56% continued to exhibit favorable outcomes: 39% were Class 1, 17% Class 2, 17% Class 3, and 28% Class 4. A favorable outcome (ie, Class 1 or 2) at 12 months was a significant predictor of continued favorable outcomes at 2 years (P <.001) and 4 years (P = .013). Favorable outcome at earlier time points (3 months for 6 months) did not significantly predict a Class 1 or 2 outcome at 4 years. In contrast, seizure-free status after 4 years was significantly associated with being seizure free as early as the first postsurgical evaluation at 3 months (P = .013). In addition, patients with simple partial seizures had a significantly greater likelihood of favorable outcome than patients with complex partial/secondarily generalized seizures. No other patient factors were significant predictors of postsurgical outcome.