High-resolution diffusion tensor imaging of the hippocampus in temporal lobe epilepsy

Salmenperä, Tuuli; Simister, Robert; Bartlett, Philippa A.; Symms, Mark R.; Boulby, Philip A.; Free, S. L.; Barker, Gareth J.; Duncan, John S.

doi:10.1016/j.eplepsyres.2006.05.020

Cited by 76 publications

(58 citation statements)

References 13 publications

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“…These results are in line with reports of elevated MD in the subacute postictal state. 27,28 Notably, group comparisons revealed increased MD mainly in the temporal portion of the tracts, whereas effects of time form last seizure were observed in the distal, extratemporal segments. Hence, analysis of tract segments allowed disentangling potential pathophysiologic mechanisms, with the temporal portion showing signs of static microstructural damage due to chronic seizure activity, whereas changes in the distal portion seem to be modulated by postictal edema.…”

Section: Results Spatial Analysis Along Tractsmentioning

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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Section: Results Spatial Analysis Along Tractsmentioning

confidence: 99%

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

et al. 2012

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“…In addition to its ability to trace out white matter pathways, DTI is often used to characterize and investigate pathological changes by measuring the amount of diffusivity and anisotropy as compared to controls, similar to analysis for quantitative relaxometry. Changes in diffusivity have been well studied in MTS with increased diffusivity and reduced anisotropy in the limbic structures shown to lateralize seizure onset (Pereira et al, 2006;Assaf et al, 2003;Salmenpera et al, 2006;Thivard et al, 2005). Furthermore, white matter abnormalities have been shown to exist in the temporal and frontal lobe white matter and along known seizure propagation pathways such as the corpus callosum, external capsule, fornix and cingulum (Gross et al, 2006;Concha et al, 2009;Focke et al, 2008).…”

Section: Discussionmentioning

confidence: 99%

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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“…However, even with the use of a high-resolution epilepsy protocol, including relaxometry of the hippocampus, almost 80% of patients in this series show no structural cause for seizure activity. It has been shown that the sensitivity can be increased slightly by using additional specialised sequences such as tractography and spectroscopy [21][22][23], but the small improvement in the detection rate of surgically amenable lesions may not justify the cost and extra scan time. It is more likely to be of benefit in those patients with refractory epilepsy where surgery is being considered as a treatment option.…”

Section: Abnormalities Related To Seizure Activitymentioning

confidence: 99%

3.0 T MRI of 2000 consecutive patients with localisation-related epilepsy

Craven

Griffiths²,

Bhattacharyya³

et al. 2012

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High-resolution diffusion tensor imaging of the hippocampus in temporal lobe epilepsy

Cited by 76 publications

References 13 publications

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

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

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

3.0 T MRI of 2000 consecutive patients with localisation-related epilepsy

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