Dysgenetic mesial temporal sclerosis: an unrecognized entity

Mesial temporal sclerosis (MTS) is the most frequently encountered lesion i n adult patients with intractable temporal epilepsy; it is found in isolati on in approximately two-thirds of surgically treated cases. Whereas the exa ct etiology of MTS is still controversial, several reports suggest that thi s pathologic lesion is both the cause and the consequence of chronic seizur es and develops progressively during childhood secondary to recurrent seizu res. In order to evaluate the clinical importance of MTS in children, we re trospectively reviewed the clinical charts of children who underwent surger y for medically intractable temporal epilepsy and report cases presenting a n amygdalo-hippocampic dual pathology. Six children aged 1.5-16 years (mean +/-SD: 7.5+/-3 years) presenting with partial complex seizures (5 cases) or extension spasms (1 case), with onset from 6 months to the age of 8.5 year s (mean seizure onset+/-SD: 3+/-5 years) underwent anterior temporal lobect omy including resection of the amygdala and hippocampus. All patients exhib ited variable degrees of severity of neuronal loss and gliosis in the amygd ala and/or hippocampus. The pathological picture of MTS was not isolated, h owever. Careful pathological examination has thus shown foci of amygdalo-hi ppocampic neuronal dysplasia in six patients, with concomitant bilaminated fascia dentata in two cases. Postoperatively, no mortality or morbidity was encountered. After a mean follow-up of 2.5 years, four patients are seizur e free. One patient had a 80% rate of improvement in seizure frequency, tho ugh still having occasional febrile convulsions. In another patient, comple x partial seizures resolved, but rare episodes of absence were still observ ed. These data are in keeping with the hypothesis that MTS could be seconda ry to repeated seizures. The analysis of this series of patients could sugg est that mesiotemporal dysplastic lesions within the amygdalo-hippocampic s tructures induce seizures, which, in turn, will favor the development of MT S during childhood. MTS could then lead to synaptic reorganization, which c an express abnormal hyperexcitability and result in more recurrent seizures . In this way a vicious circle is set up, which may explain the progression of seizures in some patients.