Abstracts

To assess the predictive diagnostic added value of MRS, PET and ictal SPECT in the pre-operative evaluation of candidates for epilepsy surgery an extensive meta-analysis from January 1992 to July 2003 was performed. From a PubMed search 78 studies presenting detailed diagnostic test results and a classified outcome of the patients were included. Studies exclusively reporting on patients with brain tumors or on children were excluded. MRS ratio decrease ipsilateral to surgical resection revealed a predictive value of 82% for good outcome (Engel Class I and II) in an unspecified population. The odds ratio of unilateral versus bilateral MRS abnormalities for seizure freedom was 4. 891 [1. 965 - 12. 172]. Ipsilateral PET hypometabolism showed a predictive value of 86% for good outcome. In patients with normal MRI the predictive value was 80%, and in patients with non-localized ictal scalp EEG 72% respectively. PET did correlate well to the other non-invasive diagnostic tests, but none of the odds ratios of any test combination was significant. The attempt failed for ictal SPECT due to insufficient literature data. Also heterogeneity among the studies and weakness regarding their study design were observed. Besides in 2 studies the additional new information for localizing the epileptogenic zone achived by MRS, PET or SPECT was not stated in the studies. The studies addressed mainly epilepsy patients of temporal lobe origin. Our data confirm that MRS, PET and ictal SPECT may be an indicator for good post-operative outcome in presurgical evaluation of drug-resistant temporal lobe epilepsy, but under cost-effectiveness aspects their role and value remained questionable and unclear. They should not be used in patients localized by ictal scalp EEG and MRI. Prospective studies limited to patients with non-localized ictal scalp EEG or to MRI-negative patients are required for validation.