Abstract
Patients with temporal lobe epilepsy (TLE) are refractory to antiepileptic drugs in about 30% of cases. Surgical treatment has been shown to be beneficial for the selected patients but fails to provide a seizure-free outcome in 20–30% of TLE patients. Several reasons have been identified to explain these surgical failures. This paper will address the five most common causes of TLE surgery failure (a) insufficient resection of epileptogenic mesial temporal structures, (b) relapse on the contralateral mesial temporal lobe, (c) lateral temporal neocortical epilepsy, (d) coexistence of mesial temporal sclerosis and a neocortical lesion (dual pathology); and (e) extratemporal lobe epilepsy mimicking TLE or temporal plus epilepsy. Persistence of epileptogenic mesial structures in the posterior temporal region and failure to distinguish mesial and lateral temporal epilepsy are possible causes of seizure persistence after TLE surgery. In cases of dual pathology, failure to identify a subtle mesial temporal sclerosis or regions of cortical microdysgenesis is a likely explanation for some surgical failures. Extratemporal epilepsy syndromes masquerading as or coexistent with TLE result in incomplete resection of the epileptogenic zone and seizure relapse after surgery. In particular, the insula may be an important cause of surgical failure in patients with TLE.
Highlights
Despite optimal medical therapy, about a third of patients with partial epilepsy continue to have recurrent seizures [1, 2]
A randomized clinical trial has shown that surgery is superior to prolonged medical therapy for patients with refractory temporal lobe epilepsy (TLE) [3]
Five major causes are commonly identified in the literature: (1) insufficient resection of mesial temporal structures, (2) insufficient or nonresection of temporal neocortex, (3) dual pathology, (4) relapse on the contralateral temporal lobe, and (5) extratemporal and temporal plus epilepsy
Summary
About a third of patients with partial epilepsy continue to have recurrent seizures [1, 2]. A randomized clinical trial has shown that surgery is superior to prolonged medical therapy for patients with refractory temporal lobe epilepsy (TLE) [3]. Surgical treatment of temporal lobe epilepsy still fails to provide a seizure-free outcome in 20–30% of these patients [4, 5]. Several studies have addressed this issue and have reported several potential causes for these failures. The reasons behind surgical failure are multiple and vary from one patient to another, and each pattern of seizure recurrence is likely to have its own explanation. This review will address each of these categories separately and report the proposed underlying mechanisms precluding seizurefree outcomes
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