Abstract
Refractory mesial temporal lobe epilepsy (mTLE) is a debilitating condition potentially amenable to resective surgery. However, between 40 and 50% patients continue to experience postoperative seizures. The development of imaging prognostic markers of postoperative seizure outcome is a crucial objective for epilepsy research. In the present study, we performed analyses of preoperative cortical thickness and subcortical surface shape on MRI in 115 of patients with mTLE and radiologically defined hippocampal sclerosis being considered for surgery, and 80 healthy controls. Patients with excellent (International League Against Epilepsy outcome (ILAE) I) and suboptimal (ILAE II–VI) postoperative outcomes had a comparable distribution of preoperative atrophy across the cortex, basal ganglia, and amygdala. Conventional volumetry of whole hippocampal and extrahippocampal subcortical structures, and of global gray and white matter, could not differentiate between patient outcome groups. However, surface shape analysis revealed localized atrophy of the thalamus bilaterally and of the posterior/lateral hippocampus contralateral to intended resection in patients with persistent postoperative seizures relative to those rendered seizure free. Data uncorrected for multiple comparisons also revealed focal atrophy of the ipsilateral hippocampus posterior to the margins of resection in patients with persistent seizures. This data indicates that persistent postoperative seizures after temporal lobe surgery are related to localized preoperative shape alterations of the thalamus bilaterally and the hippocampus contralateral to intended resection. Imaging techniques that have the potential to unlock prognostic markers of postoperative outcome in individual patients should focus assessment on a bihemispheric thalamohippocampal network in prospective patients with refractory mTLE being considered for temporal lobe surgery. Hum Brain Mapp 36:1637–1647, 2015. © 2015 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.
Highlights
Mesial temporal lobe epilepsy due to hippocampal sclerosis (HS) is the most common and most frequently operated medically intractable epilepsy disorder [Janszky et al, 2005; Wiebe and Jette, 2012]
R Keller et al r ative outcome in individual patients should focus assessment on a bihemispheric thalamohippocampal network in prospective patients with refractory Mesial temporal lobe epilepsy (mTLE) being considered for temporal lobe surgery
Some areas of cortical thickness alterations were more extensive in patients with left mTLE, including ipsilateral mesial temporal and temporo-occipital cortices
Summary
Mesial temporal lobe epilepsy (mTLE) due to hippocampal sclerosis (HS) is the most common and most frequently operated medically intractable epilepsy disorder [Janszky et al, 2005; Wiebe and Jette, 2012]. Abnormalities of subcortical regions, the thalamus and basal ganglia, have been frequently demonstrated in groups of patients with mTLE using morphometric magnetic resonance (MR) imaging [Barron et al, 2013; Bernhardt et al, 2012; Dreifuss et al, 2001; Keller and Roberts, 2008], MR diffusion tensor imaging (DTI) [Gong et al, 2008; Keller et al, 2012, 2014], MR spectroscopy [Hetherington et al, 2007], and metabolic positron emission tomography (PET) [Bouilleret et al, 2008; Juhasz et al, 1999] techniques. The thalamus and basal ganglia play important roles in controlling seizure activity throughout the brain, regardless of the location of the epileptogenic focus [Dreifuss et al, 2001]. The significance of subcortical and cortical abnormalities for postoperative seizure outcome in refractory mTLE is poorly understood
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