Epilepsy surgery in patients with bilateral temporal lobe seizures: A systematic review

Abstract

SUMMARYWe explored the association between magnetic resonance imaging (MRI) lesion, degree of seizure laterality on intracranial electroencephalography (iEEG), and seizure outcome in patients with ambiguous or presumed bilateral temporal lobe epilepsy (BiTLE) on scalp EEG. We systematically reviewed the literature using Embase and MEDLINE up to May 31, 2012. Patients with bilateral iEEG, temporal lobe surgery, and follow-up ≥1 year were included. We undertook three separate analyses on patients whose scalp EEG showed ambiguous onset or BiTLE (1) group data of those whose iEEG demonstrated unilateral TLE, (2) group data of those whose iEEG demonstrated BiTLE, (3) individual patient analysis in those with BiTLE for whom iEEG seizure laterality data were provided. Of 1,403 patients with ambiguous or presumed BiTLE on scalp EEG, 1,027 (73%) proved to have unilateral TLE on iEEG and contributed to the first analysis. Of these, 58% had Engel class I and 9% Engel class II outcomes. Of 132 patients in the second analysis (true BiTLE), Engel class I and II outcomes were achieved in 23% and 14%, respectively. Of 41 patients in the third analysis, 66% and 2% had Engel class I and II outcomes, respectively. The median proportion of seizures ipsilateral to the resection on iEEG did not differ between BiTLE patients with Engel class I-II (76%) and Engel III-IV (78%) outcomes (p = 0.87). Patients with ambiguous or independent bitemporal seizure onset on scalp EEG achieved good surgical outcomes. Overall, a significantly higher proportion of patients achieved good outcomes when iEEG showed unilateral TLE (67%) than when it showed true BiTLE (45%). However, the degree of seizure lateralization in those with BiTLE was not associated with seizure outcome, and it has a limited role in selecting the side of surgery.

Contralateral Hippocampal Stimulation for Failed Unilateral Anterior Temporal Lobectomy in Patients with Bilateral Temporal Lobe Epilepsy

“…From the early stage of epilepsy surgery, bilateral TLE has been diagnosed on the basis of clinical semiology and findings from MRI and scalp EEG [6]. However, it is not rare for patients with TLE to present with bilateral temporal lobe epileptiform discharges on scalp EEG, and only 11.5% of patients were true bilateral TLE [3]. Therefore, intracranial electrode EEG is commonly used in the diagnosis of bilateral TLE, although the use of this method is not obligatory.…”

“…On the other hand, Loesch et al [13] performed unilateral ATL in 11 patients with bilateral TLE, with 10 (90.9%) achieving postoperative Engel level I-II seizure control, and Cukiert [15] reported that all 9 patients with bilateral TLE who received unilateral ATL attained Engel level I-II seizure control 5-10 years after the procedure. Aghakhani et al [3] reviewed 1,403 patients with ambiguous or presumed bilateral TLE on scalp EEG, determining that 1,027 (73%) exhibited unilateral TLE on intracranial EEG and underwent unilateral ATL. Of these patients, 58% achieved Engel class I control, and 9% achieved an Engel class II outcome.…”

“…It is known that patients with independent spikes or sharp waves over the bilateral temporal regions do not obtain as high a rate of complete seizure control after temporal lobe surgery compared with patients with a unilateral temporal lobe focus [3,4,5]. The prognostic significance of unilateral temporal spikes in the scalp electroencephalogram (EEG) as a predictor of outcome after temporal lobe surgery has been reinforced by several studies [6,7].…”

“…However, interictal spikes or sharp waves over the bilateral temporal region are not rare [8,9,10], and autopsies of chronically institutionalized patients with clinical diagnoses of TLE have provided a spectrum of bilateral temporal pathology, with evidence of some type of bilateral temporal pathology in as many as 80% of patients and bilateral hippocampal sclerosis in 50% [11]. Furthermore, not all patients with bilateral temporal spikes experience poor seizure control, and approximately 54% become seizure free after surgery [3]. …”

“…The most pertinent concern about bilateral TLE arises from the fact that independent bilateral temporal seizures can cause surgery to fail, as after the resection of one temporal lobe seizures sometimes continue to arise from the other lateral side [2,3,4]. This phenomenon has caused controversy over whether contralateral hippocampal stimulation should be taken into consideration after the failure of unilateral ATL.…”