Abstracts

Rationale: The progressive nature of hippocampal sclerosis is still a matter of debate. Smaller MRI-studies of patients with temporal lobe epilepsy (TLE) have shown a reduction in hippocampal volumes after 3.5 years of follow-up and have found a correlation between the rate of atrophy and the number of seizures in the interscan period. However, the studies did not include healthy controls. Follow-up studies on broader patient groups have not found progressive hippocampal atrophy apart from age-related changes, except in a few individuals. We aimed to find out whether there is progressive atrophy of the hippocampus in patients with TLE that exceeds the changes seen in healthy controls, and whether the atrophy is related to the number of seizures experienced. To our knowledge, this is the first study with a follow-up period of 7 years.Methods: We performed a follow-up study of 21 patients (8 men, 13 women) with TLE and 16 healthy controls (11 men, 5 women). The patients and controls had brain MRI scans between 1995 and 2002 and again in 2006. The mean follow-up time between the scans was 7.0 years. The ipsilateral and contralateral hippocampal volumes were measured using volumetry. The difference in hippocampal volume between the first and second scan was calculated and compared with the difference in controls. The change in hippocampal volume was correlated with the number of seizures experienced between the two scans. Results: Mean age was 36.3 years for patients and 36.7 years for controls at the time of the first scan. Mean baseline hippocampal size was 4.90 cm³ for the ipsilateral hippocampus and 4.89 cm³ for the contralateral hippocampus. Mean baseline hippocampal size was 5.37 cm³ in controls. The mean reduction in hippocampal volume was 0.92 cm³ (18.8%) ipsilaterally and 0.55 cm³ (11.2%) contralaterally in patients. In controls the mean reduction in hippocampal volume was 0.62 cm³ (11.5%). Conclusions: A reduction in hippocampal volume ipsilaterally to seizure focus was seen in patients with TLE after seven years of follow-up. This was larger than the volume reduction seen in the contralateral hippocampus of patients and in healthy controls. This confirms the progressive nature of hippocampal sclerosis in TLE.