Temporal lobe epilepsy with varying severity: MRI study of 222 patients

Abstract

MRI was performed in 222 consecutive adult patients with temporal lobe epilepsy of varying severity from January 1991 to May 1993. The diagnosis of hippocampal sclerosis was established visually by three independent observers. The accuracy of visual assessment of hippocampal asymmetry was compared with volumetric measurements. Neuropathological correlations were obtained in 63 patients with refractory seizures. Temporal lobe abnormalities were observed in 180 patients (81%) as follows: hippocampal sclerosis in 122 (55%); developmental abnormalities in 16 (7.2%); tumours in 15 (6.8%); scars in 11 (5%); cavernous angiomas in 10 (4.5%); miscellaneous lesions in 6. MRI was normal or showed unrelated changes in 42 patients (19%). Visual assessment correctly lateralised hippocampal sclerosis in 79 of the 84 patients measured (94%). Temporal lobectomy confirmed the MRI data (side and aetiology) in all 63 operated patients. Patients with normal MRI had an older age of seizure onset and were more often drug-responsive than patients with hippocampal sclerosis. MRI showed temporal lobe abnormalities in 81% of epileptic patients with varying severity with good neuropathological correlation. Patients with normal MRI had a less severe form of the disease.

Clinical Magnetic Resonance Volumetry of the Hippocampus in 58 Epileptic Dogs*

“…The characteristics of hippocampal sclerosis include hippocampal atrophy and hyperintensity on T2W and FLAIR images, and hypointensity on T1WI images. [3][4][5]35,36 Hippocampal atrophy is associated with the degree of the neuronal loss from Ammon's horn, and high signal intensity on T2W images is correlated with the degree of gliosis, as well as neuronal loss. 37 The degree of hippocampal sclerosis can range from mild to extensive gliosis to neuronal loss, and, when neuronal loss and gliosis occur only in hippocampal gray matter, they may not be detected on MR images.…”

“…2,3 Hippocampal sclerosis is recognized as atrophy of the affected-side hippocampus and leads to hyperintensity on T2-weighted (T2W) or fluidattenuated inversion recovery (FLAIR) images. 3,4 Magnetic resonance (MR) volumetry of the hippocampus is useful in assessing hippocampal atrophy and the laterality of epileptic foci in epileptic patients, and is currently a common assessment method for hippocampal sclerosis in humans. [5][6][7][8] In dogs, on the other hand, imaging abnormalities are usually not observed in idiopathic epilepsy, and human-like hippocampal sclerosis and mossy fiber sprouting, a component of hippocampal sclerosis, are rare in intractable epilepsy in dogs.…”

Correlation between calbindin expression in granule cells of the resected hippocampal dentate gyrus and verbal memory in temporal lobe epilepsy

“…In many patients (48-75%), therapy-resistant TLE is associated with sclerosis of the medial temporal lobe structures [1,2]. Less frequently, TLE is related to malformation of cortical development (MCD; 13-45%) and tumors (27-33%) of the central nervous system [3].…”

[18F] Fluorodeoxyglucose–Positron-Emission Tomography and MR Imaging Coregistration for Presurgical Evaluation of Medically Refractory Epilepsy

“…However, despite these advancements, MR imaging still fails to reveal any apparent abnormality in approximately 20% of the patients with medically refractory epilepsy. 4 Patients with epilepsy and normal MR imaging findings have long been the subject of intense research. Other techniques such as positron-emission tomography (PET), ictal single-photon emission tomography, and proton spectroscopy have been used to depict abnormalities that may indicate the epileptogenic zone.…”