Dysgenetic mesial temporal sclerosis: an unrecognized entity

Abstract

Mesial temporal sclerosis (MTS) is the most frequently encountered lesion in adult patients with intractable temporal epilepsy; it is found in isolation in approximately two-thirds of surgically treated cases. Whereas the exact etiology of MTS is still controversial, several reports suggest that this pathologic lesion is both the cause and the consequence of chronic seizures and develops progressively during childhood secondary to recurrent seizures. In order to evaluate the clinical importance of MTS in children, we retrospectively reviewed the clinical charts of children who underwent surgery for medically intractable temporal epilepsy and report cases presenting an 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 years (mean seizure onset +/- SD: 3 +/- 5 years) underwent anterior temporal lobectomy including resection of the amygdala and hippocampus. All patients exhibited variable degrees of severity of neuronal loss and gliosis in the amygdala and/or hippocampus. The pathological picture of MTS was not isolated, however. Careful pathological examination has thus shown foci of amygdalo-hippocampic 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 seizure free. One patient had a 80% rate of improvement in seizure frequency, though still having occasional febrile convulsions. In another patient, complex partial seizures resolved, but rare episodes of absence were still observed. These data are in keeping with the hypothesis that MTS could be secondary to repeated seizures. The analysis of this series of patients could suggest that mesiotemporal dysplastic lesions within the amygdalo-hippocampic structures induce seizures, which, in turn, will favor the development of MTS during childhood. MTS could then lead to synaptic reorganization, which can 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.

Stereological Analysis of Amygdala Neuron Number in Autism

“…Second, most of the brains from the autism cases in the previous studies had a comorbid seizure disorder. There is substantial evidence that temporal lobe epilepsy is associated with pathology, including cell loss, of the amygdala (Pitkanen et al, 1998;Vernet et al, 2000). We eliminated this potentially confounding factor by only analyzing postmortem brains from individuals with no history of seizures.…”

Temporal lobe epilepsy: neuropathological and clinical correlations in 243 surgically treated patients

“…Our data showing a strong association between extrahippocampal malformative lesions, FS and HS suggest that malformative lesions predisposes to FS and seizures leading to HS. However the hypothesis that malformative lesions and HS share a common embryonic damage (Vernet et al, 2000;Blümcke et al, 2002) cannot be ruled out, since sophisticated methodologies such as those used by these authors were not performed. With regard to surgery it is controversial whether the lateral temporal neocortex should be removed or selective surgery on mesial regions should be performed on patients whose MRI reveals only HS.…”

Long-term outcome after surgical treatment of temporal lobe epilepsy in children

“…There is now accumulating evidence for this important clinical entity known as dual pathological entities. 60,94 That repeated seizures may render the MTS more frequently visible on MR imaging as the patient ages may also suggest a role for ongoing damage with recurring seizures, or this could reflect a certain delay in the appearance of damage at a cellular level on current neuroimaging modalities.…”