Surgical Treatment of Lesional Mesial Temporal Lobe Epilepsy.

Lesional mesial temporal lobe epilepsy (mTLE) concerns a lesion other than mesial hippocampal sclerosis present in the mesial temporal lobe and causing seizures. The lesions are usually composed of focal cortical dysplasia (FCD) or are tumorous. These are good candidates for surgical treatment. Sometimes, it is difficult to distinguish between tumors and FCD and to determine the extent of required removal. C-methionine positron emission tomography (PET) is helpful in differentiating lesions before surgery in lesional mTLE. In C-methionine PET imaging, tumors show a hot uptake, whereas FCD does not. In case of tumorous conditions, the removal of only specific lesions may be considered because the seizure outcome is dependent on complete excision of the tumor. There are several ways to safely access mesial temporal structures. The transsylvian-transcisternal approach is a good way to access the mesial structures while preserving the lateral and basal temporal structures. Actual lesions associated with epileptogenesis in FCD may be larger than they appear on magnetic resonance imaging. For this reason, evaluations to locate sufficient epileptogenic foci, including invasive studies, should be completed for FCD, and epilepsy surgery should be performed according to these results. Regardless, the ultimate goal of all epilepsy surgeries is to maximize seizure control while maintaining neurological function. Therefore, a tailored approach based on the properties of the lesion is needed.