Failed epilepsy surgery for mesial temporal lobe sclerosis: a review of the pathophysiology

Object. The object of the current study was to review the electrophysiology and pathological substrate of failed temporal lobe surgery in patients with mesial temporal sclerosis. Methods. A systematic review of the literature was performed for the years 1999-2010 to assess the cause of failure and to identify potential reoperation candidates. Results. Repeat electroencephalographic evaluation documenting ipsilateral temporal lobe onset was the most frequent cause for recurrent epileptogenesis, followed by contralateral temporal lobe seizures. Less frequently, surgical failures demonstrated an electroencephalogram that was compatible with extratemporal localization. The generation of occult or new epileptogenic zones as well as residual epileptogenic tissue could explain these findings. Conclusions. The outcome of temporal lobe surgery for epilepsy is challenged by a somewhat consistent failure rate. Reoperation results in improved seizure control in properly selected patients. A detailed knowledge of the pathophysiology is beneficial for the reevaluation of these patients. (http://thejns.org/doi/abs/10.3171/2011.12.FOCUS11318)