Predicting surgical outcomes in temporal lobe epilepsy

US researchers have identified patterns of hippocampal atrophy that predict surgical outcomes in patients undergoing anteromesial temporal resection for temporal lobe epilepsy.The researchers say that few clinical characteristics have been shown to have surgical prognostic value in these patients, although a personal history of status epilepticus has been associated with poorer outcome. They used surface-based anatomical mapping to measure patterns of hippocampal atrophy in 40 patients with medial temporal lobe epilepsy and hippocampal sclerosis who were to undergo surgery. They then analysed which anatomical features correlated with better or poorer surgical outcomes. Preoperative three-dimensional maps of hippocampal atrophy were constructed from consecutive coronal MRI sections, allowing the regions to be visualised and measured. The authors used surface-based statistics to compare features of hippocampal anatomy in patients who were seizure-free and those who continued to have seizures after the surgery.Compared with the seizure-free group (n=30), the group that continued to have seizures (n=10) had greater diffuse atrophy in the ipsilateral hippocampus, but the contralateral side showed more region-specific atrophy, particularly in the anterior and lateral aspects of the hippocampus. The authors consider that the atrophic regions may indicate areas of increased epileptogenicity, contributing to poorer surgical outcomes. They say, "We suggest that with disease progression, the sclerotic ipsilateral hippocampus may already be diffusely damaged (i.e., a floor effect), whereas the contralateral hippocampus may exhibit damage only in regions with the greatest susceptibility for epileptogenesis?Seizure propogation from one hippocampus to the other over time may lead to damage first in the most vulnerable areas of the contralateral hippocampus." The authors point out that their clinical data showed no features that reliably predicted surgical outcome in their patients, highlighting the lack of clinical characteristics of surgical prognostic value in this population.Reference...