Abstracts

Rationale: Mesial Temporal Lobe Epilepsy (MTLE) is often associated with a progressive course and frequently displays pharmacoresistance, but a substantial proportion of patients show a benign course. There is little knowledge about which factors contribute to progression, and whether and to what degree hippocampal sclerosis (HS) increases with time. The aim of this study is to follow the development of HS prior to surgery.Methods: This study includes patients operated for histologically proven MTLE at Oslo University Hospital - Rikshospitalet between 2008-2013. For each patient the first (time 1) and the last (time 2) preoperative MRI is selected and scrutinized by an experienced neuroradiologist blinded to both time points and hemisphere scheduled for surgery. T2 signal intensity and hippocampal volume changes are assessed by a predetermined score in both hippocampi at three different locations (caput, corpus, cauda), and are compared at time 1 and 2.Results: The study material consists of 22 patients of whom 14 (64%) are women and 14 (64%) have HS with left-sided localization. Median age at surgery is 40,5 years (range 5-61). Median interval between time 1 and time 2 is 3,4 years (range 1-8,5). In 9 (41%) of cases no progression can be detected, while 13 (59%) show progression: 2 (9%) possible, 2 (9%) probable and 9 (41%) definite progression. The mean score of T2-signal intensity and atrophy at time 1 is 56% higher in the former group, and the monitoring time is twice as long in the latter group. Thus hippocampal sclerosis increases at longer follow-up, indicating continuous progression. However, in cases with pronounced sclerosis already at time 1, no further significant progression can be detected. Among patients with a progressive course 11/13 (85%) had left-sided HS versus 3/9 (33%) in the group with no MRI correlate of progression.Conclusions: According to these preliminary data MTLE displays radiological progression in a large proportion of patients. However not all patients show clear signs of progression, especially those with existing severe changes already at early time point. Predominance of progression in patients with left-sided lesions is interesting and requires further investigation in larger cohorts.