Abstracts

Abnormalities of the anterior temporal lobe in patients with intractable temporal lobe epilepsy and mesial temporal sclerosis (MTS) have been discussed in the literature. The cause of these MRI abnormalities has not been established. The aim of this study is to evaluate the diagnostic relevance of loss of the gray-white matter differentiation (LGWD) in the temporal pole (TP) on coronal fluid-attenuated inversion-recovery (FLAIR) imaging in patients with MTS and age-matched control subjects.
Sixty-five patients with MTS visually detected by MRI and twenty normal control subjects were included in this study. Only the first four or five coronal FLAIR images of the TP were visually assessed by two experienced neuroradiologists. Observers were unaware of lateralizing electroclinical data and the images did not include the hippocampus. Patients and control subjects were divided into two groups according to LGWD on FLAIR images. This abnormality consists of an indistinct gray-white matter demarcation and/or an increased signal intensity of the TP. The topography of the LGWD in the TP was also evaluated, defined as occurring in the anteromedial region, in the lateral region, or both. The associations between LGWD and MRI signs of hippocampal sclerosis, history of initial precipitant insults (IPI), age at onset, seizure frequency and duration of illness were surveyed.
The MRI feature of LGWD was observed in 48 (74%) out of the 65 patients with MTS. There was no LGWD in the 20 normal subjects. Considering the unilateral hippocampal abnormalities, present in 59 patients (91%), they were found in the same temporal lobe in all patients with unilateral LGWD. Bilateral hippocampal sclerosis was detected in 6 patients (9%) and in 5 of them (83%) we found LGWD ipsilateral to the more affected hippocampus. The only case in which both hippocampi were affected equally, LGWD was found on the side pointed out by electroclinical data. All 48 patients with LGWD had the abnormalities in the medial region of TP, being purely medial in 35 (73%) and involving both medial and lateral regions in 13/48 (27%). Presence of IPI, represented mainly by febrile seizures, was correlated with LGWD since it was found in 21out of 48 patients (44%) with LGWD and in 5 out of 17 (29%) of those without. LGWD failed to correlate with age at onset, seizure frequency, duration of illness and region of involvement of the TP.
The MRI feature of LGWD can improve the visual diagnosis of MTS and it is a valuable additive sign for correct seizure lateralization, particularly using coronal FLAIR sequences which include the anterior temporal lobe in full. In this series LGWD had a medial predominance and was related to the presence of IPI.
[Supported by: Funda[ccedil][atilde]o de Amparo [agrave] Pesquisa do Estado de S[atilde]o Paulo.]