Abstracts

Hippocampal sclerosis (HS) is the lesion most frequently described in temporal lobe epilepsy. HS can be detected in-vivo using magnetic resonance imaging (MRI). The presence of HS is believed to predict an increased risk of medically refractory epilepsy. Most studies of HS deal with patients under pre-surgical evaluation, and consequently probably reflect the more serious cases.The few existing studies on broader patient groups rely on qualitative MRI. We performed a retrospective study of quantitative MRI findings in partial epilepsy, in order to dertermine the frequency of HS and its impact on seizure control. We analysed data from 784 consecutive MR-scans performed at the MR-Center, Skejby Sygehus, as part of the investigations for partial epilepsy in the period 1995-2003. Patients were aged 15-50 years and had been referred from the Department of Neurology, Aarhus University Hospital, or from a private neurologist in the County of Aarhus, the only local sites for investigation of newly-diagnosed epilepsy. All MR-scans (1.5 T) included volumetry and T2-relaxometry of the hippocampal region. Patients were categorized into 5 groups according to MRI-findings: . HS (atrophy and ipsilateral raised T2 signal), . Unilateral hippocampal atrophy only, . Unilaterally raised T2 signal, . Bilaterally raised T2 signal, and . Normal MRI.
Clinical information regarding age of onset, duration, and seizure frequency was extracted from Epibase, a prospective database in which all epilepsy patients have been systematically registered since 1999. Results are based on this preliminary information, and information on all patients is currently being extracted from medical records. Seven hundred-fifty-three persons were scanned. 31 patients had two scans. Mean age was 31 years. Hippocampal changes were found in 27% of scans. HS was detected in 40 (5%), unilateral atrophy alone in 33 (4%), unilaterally raised T2 signal in 99 (13%) and bilaterally raised T2 signal in 41 scans (5%). Left HS was more common than right (26 vs.14 scans, p= 0.04). The age of onset tended to be lower (13 vs. 18 years, NS), and the duration of epilepsy was longer in the HS group compared to patients with other unilateral changes (group 2 and 3)(21 vs 14 years, p[lt]0.05). Seizure-freedom was rarer in patients with HS than in the groups with other unilateral changes (24% vs. 45%, p[lt]0.05), and more patients with HS had frequent seizures compared to patients with other unilateral change and to normals (62% vs. 36% and 33%, p[lt]0.05). HS, defined as atrophy and raised T2 signal on the same side, was found in 5% of our patients with partial epilepsy. Overall, unilateral hippocampal changes were present in 22%. Hippocampal sclerosis shown by quantitative MRI was associated with lower age of onset and a greater risk of severe, intractable epilepsy. (Supported by Aarhus University Hospital, The Danish Epilepsy Society)