Asymmetrical extra-hippocampal grey matter loss related to hippocampal atrophy in patients with medial temporal lobe epilepsy

Bonilha, Leonardo; Rorden, Chris; Halford, Jonathan J.; Eckert, Mark A.; Appenzeller, Simone; Cendes, Fernando; Li, Li Min

doi:10.1136/jnnp.2006.103994

Cited by 110 publications

(134 citation statements)

References 29 publications

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“…Similar results have been seen with voxel-based morphometry (Bonilha et al, 2007) with a relationship of atrophy asymmetry in hippocampal atrophy. These differences between LTLE and RTLE have been speculated to be due to greater vulnerability of the left hemisphere to early injury and the progressive effects of seizures (Kemmotsu et al, 2011), or a combination of architectural, connectivity, physiological and developmental differences between the hemispheres (Keller et al, 2012), however, further studies are required to investigate the cause of this asymmetry.…”

Section: Discussionsupporting

confidence: 87%

Quantitative relaxometry and diffusion MRI for lateralization in MTS and non-MTS temporal lobe epilepsy

et al. 2014

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We developed novel methodology for investigating the use of quantitative relaxometry (T1, T2) and diffusion tensor imaging (DTI) for lateralization in temporal lobe epilepsy. Patients with mesial temporal sclerosis confirmed by pathology (N=8) and non-MTS unilateral temporal lobe epilepsy (N=6) were compared against healthy controls (N=19) using voxel-based analysis restricted to the anterior temporal lobes, and laterality indices for each MRI metric (T1, T2, fractional anisotropy (FA), mean diffusivity, axial and radial diffusivity) were computed based on the proportion of significant voxels on each side. The diffusivity metrics were the most lateralizing MRI metrics in MTS and non-MTS subsets, with significant differences also seen with FA, T1 and T2. Patient-specific multi-modal laterality indices were also computed and were shown to clearly separate the left-onset and right-onset patients. Marked differences between leftonset and right-onset patients were also observed, with left-onset patients exhibiting stronger laterality indices. Finally, neocortical abnormalities were found to be more common in the non-MTS patients. These preliminary results on a small sample size support the further investigation of quantitative MRI and multi-modal image analysis in clinical determination of seizure onset.The presence of more neocortical abnormalities in the non-MTS group suggests a role in seizure onset or propagation and motivates the investigation of more sensitive histopathological analysis to detect and delineate potentially subtle neocortical pathology.

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Section: Discussionsupporting

confidence: 87%

Quantitative relaxometry and diffusion MRI for lateralization in MTS and non-MTS temporal lobe epilepsy

et al. 2014

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“…[1][2][3] Conversely, white matter (WM) morphometry has shown atrophy 1,4,5 and increased T2 signal intensity, 6,7 more restricted to frontotemporal regions ipsilateral to the seizure focus.…”

mentioning

confidence: 99%

Spatial patterns of water diffusion along white matter tracts in temporal lobe epilepsy

et al. 2012

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Objectives: Diffusion tensor imaging (DTI) tractography has shown tract-specific pathology in temporal lobe epilepsy (TLE). This technique normally yields a single value per diffusion parameter per tract, potentially reducing the sensitivity for the detection of focal changes. Our goal was to spatially characterize diffusion abnormalities of fasciculi carrying temporal lobe connections. Methods:We studied 30 patients with drug-resistant TLE and 21 healthy control subjects.Twenty-four patients underwent DTI toward the end of video-EEG telemetry, with an average of 50 Ϯ 54 hours between the last seizure and DTI examination. After manual dissection of the uncinate and inferior longitudinal and arcuate bundle, they were spatially matched based on their distance to the temporal lobe, providing between-subject correspondence of tract segments. We evaluated point-wise differences in diffusion parameters along each tract at group and subject levels.Results: Our approach localized increased mean diffusivity restricted to or more prominent within the ipsilateral temporal lobe. These abnormalities tapered off as tracts exited the temporal lobe. We observed that the shorter the interval between the last seizure and DTI, the higher the mean diffusivity (MD) of the ipsilateral tracts. Linear discriminant analysis of tract segments correctly lateralized 87% of patients. Conclusions:The centrifugal pattern of white matter diffusion abnormalities probably reflects astrogliosis and microstructure derangement related to seizure activity in the vicinity of the focus. The negative correlation between the interval from last seizure and MD suggests a role for postictal vasogenic edema. The ability to assess tracts segmentally may contribute to a better understanding of the extent of white matter pathology in epilepsy and assist in the presurgical evaluation of patients with TLE, particularly those with unremarkable conventional imaging results. Neurology ® 2012;79:455-462 GLOSSARY DTI ϭ diffusion tensor imaging; FA ϭ fractional anisotropy; FWHM ϭ full-width at half-maximum; MD ϭ mean diffusivity; TE ϭ echo time; TLE ϭ temporal lobe epilepsy; TR ϭ repetition time; WM ϭ white matter.

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“…Findings of WM diffusion alterations have also been complemented by gray matter disruption. These studies have demonstrated bilateral extensive cortical gray matter volume loss in MTLE-HS [35] which is greater in patients with left sided disease [36]. The extant of gray matter disruption is closely related to the start of the disease [37] and also more severe in regions that are anatomically and functionally connected to the hippocampus [38,39].…”

Section: Discussionmentioning

confidence: 96%

Age at onset and seizure frequency affect white matter diffusion coefficient in patients with mesial temporal lobe epilepsy

Nagy

Horváth

Perlaki

et al. 2016

Epilepsy & Behavior

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SummaryIn mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS), structural abnormalities are present not only in the hippocampus, but also in the white matter with ipsilateral predominance. Although the timing of epilepsy onset is commonly associated with clinical and semiological dissimilarities, limited data exist regarding white matter diffusion changes with respect to age at epilepsy onset. The aim of this study was to investigate diffusion changes in the white matter of unilateral MTLE-HS patients with respect to clinical parameters and to compare them to an age-and sex matched healthy control group. Apparent diffusion coefficients (ADCs) were derived using mono-exponential approaches from 22 (11 early and 11 late age at onset) unilateral MTLE-HS patients and 22 age-and sex matched control subjects after acquiring diffusion-weighted images on a 3T MRI system. Data were analyzed using two-tailed t-tests and multiple linear regression models. In the early onset MTLE-HS group ADC was significantly elevated in the ipsilateral hemispheric (p=0.04) and temporal lobe white matter (p=0.01) compared to controls. These differences were not detectable in late onset MTLE-HS patients. ADC of the early onset MTLE-HS group was negatively related to age at epilepsy onset in the ipsilateral hemispheric white matter (p=0.03) and the uncinate fasciculus (p=0.03), while in late onset patients ADC was no longer dependent on age at epilepsy onset itself, but rather on the seizure frequency in the ipsilateral uncinate fasciculus (p=0.03). Such diffusivity pattern has been associated with chronic white matter degeneration, reflecting myelin loss and higher extracellular volume which are more pronounced in the fronto-temporal regions and also depends on clinical features. In the early onset group, the timing of epilepsy seems to be the major cause of white matter abnormalities while in late onset disease it has a secondary role in provoking diffusion changes.

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Asymmetrical extra-hippocampal grey matter loss related to hippocampal atrophy in patients with medial temporal lobe epilepsy

Cited by 110 publications

References 29 publications

Quantitative relaxometry and diffusion MRI for lateralization in MTS and non-MTS temporal lobe epilepsy

Quantitative relaxometry and diffusion MRI for lateralization in MTS and non-MTS temporal lobe epilepsy

Spatial patterns of water diffusion along white matter tracts in temporal lobe epilepsy

Age at onset and seizure frequency affect white matter diffusion coefficient in patients with mesial temporal lobe epilepsy

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