Combined 18F-FDG-PET and diffusion tensor imaging in mesial temporal lobe epilepsy with hippocampal sclerosis

Abstract

ObjectivesSeveral studies using 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) or diffusion tensor imaging (DTI) have found both temporal and extratemporal abnormalities in patients with mesial temporal lobe epilepsy with ipsilateral hippocampal sclerosis (MTLE-HS), but data are lacking about the findings of both techniques in the same patients. We aimed to determine whether the extent of 18F-FDG-PET hypometabolism is related to DTI abnormalities.MethodsTwenty-one patients with MTLE-HS underwent comprehensive preoperative evaluation; 18 (86%) of these underwent epilepsy surgery. We analyzed and compared the pattern of white matter (WM) alterations on DTI and cortical hypometabolism on 18F-FDG-PET.ResultsWe found widespread temporal and extratemporal 18F-FDG-PET and DTI abnormalities. Patterns of WM abnormalities and cortical glucose hypometabolism involved similar brain regions, being more extensive in the left than the right MTLE-HS. We classified patients into three groups according to temporal 18F-FDG-PET patterns: hypometabolism restricted to the anterior third (n = 7), hypometabolism extending to the middle third (n = 7), and hypometabolism extending to the posterior third (n = 7). Patients with anterior temporal hypometabolism showed DTI abnormalities in anterior association and commissural tracts while patients with posterior hypometabolism showed WM alterations in anterior and posterior tracts.ConclusionsPatients with MTLE-HS have widespread metabolic and microstructural abnormalities that involve similar regions. The distribution patterns of these gray and white matter abnormalities differ between patients with left or right MTLE, but also with the extent of the 18F-FDG-PET hypometabolism along the epileptogenic temporal lobe. These findings suggest a variable network involvement among patients with MTLE-HS.

Impaired vigilance networks in temporal lobe epilepsy: Mechanisms and clinical implications

“…These include problems with executive function, cognitive processing, concentration, and social recognition . Furthermore, mTLE patients demonstrate diffuse neocortical hypometabolism, numerous brain connectivity perturbations, and multifocal gray matter atrophy . In one study using voxel‐based morphometry analysis of serial magnetic resonance imaging (MRI) scans in mTLE patients, gray matter reduction was noted not only in limbic structures, but also in frontal, parietal, and occipital cortices, as well as bilateral thalamus (Figure ) .…”

“…[10][11][12] Furthermore, mTLE patients demonstrate diffuse neocortical hypometabolism, numerous brain connectivity perturbations, and multifocal gray matter atrophy. 3,13,14 In one study using voxel-based morphometry analysis of serial magnetic resonance imaging (MRI) scans in mTLE patients, gray matter reduction was noted not only in limbic structures, but also in frontal, parietal, and occipital cortices, as well as bilateral thalamus (Figure 1). 15 These observations may suggest a common subcortical source (or sources) of widespread network dysfunction in mTLE.…”

18F-FDG PET-guided diffusion tractography reveals white matter abnormalities around the epileptic focus in medically refractory epilepsy: implications for epilepsy surgical evaluation

“…Surgery can fail to prevent seizures when the EF is not properly delineated or detected prior to resection. Additionally, poor surgical outcomes can occur due to unknown interactions between the EF and surrounding neural networks (Aparicio et al 2016).…”

“…Recent advances in medical imaging have seen the increased clinical use of magnetic resonance imaging (MRI) and positron emission tomography (PET) to non-invasively locate the EF and map out the structure and function of surrounding brain regions. Anatomical MRI can detect structural lesions responsible for seizures in about 60% of MRE patients (Burneo et al 2015), while other advanced MRI techniques, such as diffusion tensor imaging (DTI), can be used to effectively characterize the EF and its relationships with surrounding brain regions (Aparicio et al 2016;Jiang et al 2017). DTI non-invasively characterizes tissue microstructure by providing a three-dimensional model of water diffusion in the brain (Basser and Jones 2002;Jones and Cercignani 2010).…”

“…DTI non-invasively characterizes tissue microstructure by providing a three-dimensional model of water diffusion in the brain (Basser and Jones 2002;Jones and Cercignani 2010). In addition, DTI can be used to investigate the structural connectivity of neural networks through mapping out diffusion along white matter (WM) fiber pathways (Le Bihan et al 1986;Le Bihan 2006;Aparicio et al 2016;Sivakanthan et al 2016). WM pathways can be characterized using DTI-derived parameters, which are extracted from the diffusion tensor used to model water diffusion at each voxel in the brain.…”