van Paesschen, Wim; (1997) Quantitative magnetic resonance imaging and neuropathology of the hippocampus in temporal lobe epilepsy. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Background. Hippocampal sclerosis (HS) is the most common cause of intractable temporal lobe epilepsy (TLE). Hippocampal atrophy and an increased T2-weighted signal are MRI characteristics of HS. MRI-based hippocampal volume (HCV) and hippocampal T2 (HCT2) measurement allow a quantitative description of HS. Aims. 1. to establish a 3-D microscopic counting technique to quantify neuronal and glial cell densities of hippocampal neuronal cell layers, 2. to correlate these densities with HCT2 and HCV, 3. to describe the spectrum of HS, 4. to establish amygdala T2 (AT2) mapping and its clinical correlations, 5. to evaluate single voxel proton magnetic resonance spectroscopy in MRI-negative intractable TLE, 6. To establish MRI-based etiologies of newly diagnosed localization-related epilepsy, 7. To conduct a prospective, longitudinal quantitative MRI study of the patients with newly diagnosed epilepsy to elucidate the etiology and pathogenesis of HS. Methods. A total of 207 patients with localization-related epilepsy and 39 control subjects were studied. Seventy-nine of these patients underwent surgery for intractable localization-related epilepsy. MR imaging, including HCT2 and AT2 maps, images for HCV studies, FLAIR, and MR spectroscopy (MRS) were obtained on a 1.5 T Siemens SP63 Magnetom scanner. For the neuropathological studies, a 3-D counting technique was used. Results. HCT2 was related to damage in the CAl and the hilus, and HCV to damage in CAl-CA3 and the hilus. In a group of 100 patients with intractable TLE (foreign tissue lesions excluded), 5% had anterior HS, about 50% unilateral diffuse HS, 10% bilateral diffuse HS, 20% an isolated amygdale abnormality and 6 of 7 patients with apparent MRI-negative TLE had an abnormality on MRS. Ten percent of 63 patients with newly diagnosed localization-related epilepsy had HS, and 14% had other MRI abnormalities. The early prognosis of patients with HS was worse with respect to seizures compared with patients with other MRI findings. Progressive MRI-based hippocampal changes were detected in 3 patients after one year. Conclusion. This study validates the neuropathological basis of quantitative hippocampal MRI and its use in the study of patients with epilepsy.

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