Short communicationLong term outcomes in patients with preoperative generalized interictal epileptiform abnormalities following amygdalohippocampectomy
Introduction
Resection of mesial temporal lobe structures is an established therapy for select patients with medically refractory temporal lobe epilepsy (TLE) (Wiebe et al., 2001). The presence of focal interictal epileptiform discharges (IEDs) lateralized to the side of seizure onset has been identified as a favorable prognostic factor in these patients (Radhakrishnan et al., 1998). Conversely, it is often assumed that the presence of generalized IEDs precludes resective surgery. This assumption has been proven false in children with seizure types such as infantile spasms and continuous spike wave in slow wave sleep. Despite their generalized EEG appearances, the seizures in some of these children are secondary to focal pathology amenable to resections (Gupta et al., 2007, Wyllie et al., 2007, Loddenkemper et al., 2009, Chugani et al., 2010). However, surgical outcomes in adult patients with generalized IEDs and focal pathology has been less robustly explored. The purpose of our study was to determine the long term outcomes in patients with TLE and generalized IEDs on preoperative electroencephalograms (EEG) who underwent amygdalohippocampectomies.
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Methods
We retrospectively reviewed the EEG reports of all 608 patients who underwent amygdalohippocampectomies for medically refractory TLE at our institution from 1989 to 2000. We selected those patients who demonstrated generalized IEDs on any preoperative scalp EEG for further analysis. Generalized IEDs were defined as the occurrence of generalized bilateral synchronous spike, or polyspike, and wave discharges on the interictal EEG. One patient also had a preoperative EEG showing modified
Preoperative patient characteristics
Twenty one patients were identified using the criteria specified above; 11 (52.4%) were female. One patient had undergone a focal resection of a right temporal grade 1 ganglioglioma prior to amygdalohippocampectomy. The mean duration of epilepsy prior to amygdalohippocampectomy was 22.4 ± 13.8 years (range 2–52 years). The mean age at the time of surgery was 28.1 ± 12.3 years (range 10–54 years). The mean duration of postoperative follow up was 94.8 ± 55.3 months (range 24.3–244 months). Preoperative
Conclusions
Our findings indicate that the presence of generalized IEDs in select patients with TLE being considered for amygdalohippocampectomy does not automatically portend a poor prognosis. The majority (57.1%) of patients in our cohort had favorable outcomes despite their preoperative generalized EEG findings. Seizure freedom was significantly associated with a history of aura prior to seizure onset and lack of generalized IEDs on postoperative EEG. Such data suggest that generalized IEDs in these
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