Mesial temporal sclerosis: pathogenesis, diagnosis, and management. Mesial temporal sclerosis (MTS) is probably the most common symptomatic pathologic entity--alone or mixed with other pathologic features--for seizures of temporal lobe origin. The pathophysiology of MTS, including any genetic influence, needs clarification. A characteristic ictal expression for seizures of MTS origin appears not to exist. The majority of patients (78%) with postresection MTS who are seizure-free have tightly localized interictal abnormalities restricted to F7/F8, Sp1/Sp2, T3/T4, and T5/T6 more than 96% of the time. MRI abnormalities may be seen in 55% of patients with MTS if both "hard" and "soft" criteria are used or in 20% when only "hard" criteria are used. The neuropsychologic evaluation of patients with MTS, which includes intracarotid amobarbital test (IAT), may prove to be increasingly useful in identifying patterns of cognitive deficit that correlate with enhancement of both lateralizing and localizing preoperative information. 