MRI in patients with temporal lobe epilepsy: correlation between MRI findings and clinical features

There have been many X-ray computed tomography (CT) studies on epilepsy in the literature. However, mesial temporal sclerosis, known to form an important pathology of temporal lobe epilepsy, has not been visualized by CT, while magnetic resonance imaging (MRI) has enabled it to be depicted to some extent. Various views exist as to the MRI visualization of mesial temporal sclerosis. Furthermore, only few papers have adequately dealt with clinical features in relation to MRI findings. This study attempted to investigate MRI findings on temporal lobe epilepsy, and then correlate them with clinical variables such as age, duration of illness, past history and seizure frequency. MRI was performed on 45 patients with temporal lobe epilepsy of unknown etiology (24 males and 21 females) with a 0.5 tesla imager and/or a 1.5 tesla imager. Focal abnormalities of signal intensity and dilatation of the inferior horns of lateral ventricles were evaluated on MR images. Six patients had unilateral, mesial temporal high signal areas on T2-weighted images and/or proton density-weighted images at both transverse and coronal views. CT and T1-weighted imaging showed no abnormality in and around the area. These hyperintense mesiotemporal lesions were all in the same side of the epileptogenic focus as shown by electroencephalography. The frequency of partial seizures was significantly higher in these patients than in those without the finding. Three patients had febrile convulsions. It was thought highly likely that this hyperintense area might represent the MRI visualization of mesial temporal sclerosis. Ten patients revealed slight dilatations of the inferior horns of the lateral ventricles. Statistical examinations showed that these patients were also significantly older in age and of later onset. Six patients with unilateral dilatations were significantly younger in age than four with bilateral dilatations. The duration of epilepsy was longer in the latter than in the former. Unilateral dilatation may at least indirectly reflect lesions of the mesial temporal lobe, but bilateral dilatations may be findings related to aging and/or long illness duration. Nine patients had small multiple high signal areas in the white matters of the extratemporal areas, mainly in the parietal lobes. Seizure onsets of these patients were later and the ages were older, which was statistically significant. They did not differ in other clinical features. These high signal areas were probably of vascular origin, not directly related to epilepsy.(ABSTRACT TRUNCATED AT 400 WORDS)