Objectives: To investigate the use of whole brain voxel based morphometry (VBM) and stereological analysis to study brain morphology in patients with medically intractable temporal lobe epilepsy; and to determine the relation between side, duration, and age of onset of temporal lobe epilepsy, history of childhood febrile convulsions, and grey matter structure. Methods: Three dimensional magnetic resonance images were obtained from 58 patients with left sided seizure onset (LSSO) and 58 patients with right sided seizure onset (RSSO), defined using EEG and foramen ovale recordings in the course of presurgical evaluation for temporal lobectomy. Fifty eight normal controls formed a comparison group. VBM was used to characterise whole brain grey matter concentration, while the Cavalieri method of modern design stereology in conjunction with point counting was used to estimate hippocampal and amygdala volume. Age and sex were used as confounding covariates in analyses. Results: LSSO and RSSO patients showed significant reductions in volume (using stereology) and grey matter concentration (using VBM) of the hippocampus, but not of the amygdala, in the presumed epileptogenic zone when compared with controls, but hippocampal (and amygdala) volume and grey matter concentration were not related to duration or age of onset of epilepsy. LSSO and RSSO patients with a history of childhood febrile convulsions had reduced hippocampal volumes in the presumed epileptogenic zone compared with patients without such a history. Left amygdala volume was also reduced in LSSO patients with a history of childhood convulsions. VBM results indicated bilateral thalamic, prefrontal, and cerebellar GMC reduction in patients, which correlated with duration and age of onset of epilepsy. Conclusions: Hippocampal sclerosis is not necessarily the consequence of recurrent temporal lobe seizures. A major cause of hippocampal sclerosis appears to be an early aberrant neurological insult, such as childhood febrile seizures. Secondary brain abnormalities exist in regions outside the presumed epileptogenic zone and may result from recurrent seizures. H ippocampal sclerosis is the most common finding in patients with medically intractable temporal lobe epilepsy.1 However, the relation between the duration of epilepsy and hippocampal sclerosis is not fully understood. Some cross sectional research has found evidence for progressive hippocampal volume loss in patients with temporal lobe epilepsy, [2][3][4][5] suggesting that hippocampal atrophy is a consequence of recurrent temporal lobe seizures. Conversely, others have found no relation between hippocampal volume and duration of epilepsy, 6 7 which suggests that hippocampal abnormalities do not result from repeated seizures. Hippocampal sclerosis has been related to the age of onset of epilepsy and a history of childhood febrile convulsions in some studies.3 7 However, although atrophy of the amygdala, 8 9 entorhinal cortex, 10-12 parahippocampal gyrus, 13 14 lateral temporal lobe, 15 16 and thalamus 17 h...

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Summary:Purpose; Diffusion tensor imaging allows the quantitative assessment of the microstructural organization of tracts in vivo (MR tractography). We used the new technique of MR tractography to demonstrate the effects of temporal lobectomy on the optic radiation.Methods: Spatially normalised maps encoding magnitude of the bias (anisotropy) of diffusion of three patients with temporal lobe resections were compared with spatially normalised diffusion maps of 22 control subjects. All three patients were operated on for the treatment of medically intractable temporal lobe epilepsy and had a normal neurologic examination before surgery. One patient had an amygdalocorticectomy. Two patients had standard en bloc resections, one of whom developed a homonymous hemianopia after surgery.Results: In the patient with hemianopia, a significant reduction of diffusion anisotropy (greater than mean ? 2 SD) consistent with wallerian degeneration was demonstrated in the optic radiation on the side of the temporal lobectomy, extending from the temporal to the occipital lobe. In the other patient with standard en bloc resection but clinically no hemianopia, the optic radiation was only marginally affected. In the third patient (amygdalocorticectomy), the diffusion anisotropy was within the normal range in the expected position of the optic radiation.Conclusions; Our findings show that MR tractography may be a useful tool to demonstrate wallerian degeneration in the optic radiation after temporal lobectomy in patients with hemianopia. This is the first time that this new method has been applied in postoperative imaging; it enables us to visualise the morphologic correlate of dysfunctional pathways after epilepsy surgery in vivo. The potential for using MR tractography to study other aspects of epilepsy is discussed. Key Words: MR tractography-Diffusion anisotropy-Intractable temporal lobe epilepsy.Temporal lobectomy is the most common surgical procedure performed for medically refractory symptomatic epilepsy. The optic radiation can be damaged during surgery, resulting in visual field defects. The clinical consequences of temporal lobectomy with regard to visual field defects range from quadrantanopia, which is commonly seen in en bloc resections, to hemianopia, if the resection extends more posteriorly (1). The aim of this study was to investigate the microstructural changes in the optic radiation after temporal lobectomy. We used diffusion tensor imaging (DTI), a new magnetic resonance (MR) technique suitable for the visualization of tracts (MR tractography) (2-4).Accepted January 6, 1999. Address correspondence and reprint requests to Dr. U. Wieshmann at National Society for Epilepsy, MRI Unit, Chalfont St. Peter, Gerrards Cross, Bucks SL9 ORJ, U.K. METHODS SubjectsOne patient with homonymous hemianopia and two patients with clinically full visual fields were selected for this study to compare the optic radiation of patients with and without clinical deficit after surgery. Twenty-two control subjects (14 men and seven women; m...

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