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Table of Contents    
COMMENTARY
Year : 2016  |  Volume : 64  |  Issue : 6  |  Page : 1245-1246

Diffusion tensor imaging: Opening new possibilities in temporal lobe epilepsy


1 Department of Neurology, Geetanjali Medical College, Udaipur, Rajasthan, India
2 Department of Neuroradiology, Geetanjali Medical College, Udaipur, Rajasthan, India

Date of Web Publication11-Nov-2016

Correspondence Address:
Abbas Ali Saifee
Department of Neurology, Geetanjali Medical College, Udaipur, Rajasthan
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.193769

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How to cite this article:
Saifee AA, Khamesra R, Kundu RK. Diffusion tensor imaging: Opening new possibilities in temporal lobe epilepsy. Neurol India 2016;64:1245-6

How to cite this URL:
Saifee AA, Khamesra R, Kundu RK. Diffusion tensor imaging: Opening new possibilities in temporal lobe epilepsy. Neurol India [serial online] 2016 [cited 2019 Jul 20];64:1245-6. Available from: http://www.neurologyindia.com/text.asp?2016/64/6/1245/193769


Temporal lobe epilepsy (TLE) is a common affliction across all ages, genders, and ethnicities. It has been widely studied among different population groups. Specifically, its effect on speech, language, and memory impairment, as well as its role in cognitive function decline has been evaluated and examined exhaustively. The traditional tool of examination is magnetic resonance imaging, and the traditional anatomical site examined is the gray matter.

The work presented in this article breaks new ground on both these fronts. It shelves the traditional chartered track for unbeaten ones and thus opens new frontiers of knowledge about the hippocampus, TLE, and neuroradiology.[1]

The article presents a study that uses diffusion tensor imaging (DTI), as the tool, mean diffusivity, as the relevant parameter, and white matter, as the site of primary examination. The neuroradiological data of the clinical study were collected for a group of TLE patients and a control group, all of whom met the well-defined eligibility criteria. Analysis was done vide DTI studio software and was correlated with clinical findings.

The study proposes a new hypothesis on the etiology of cognitive function impairment in TLE patients. It opens up new possibilities on the diagnosis, clinical assessment of gravity, and treatment. The hypothesis has been clearly defined, the materials, methods, statistical, and software tools have been unambiguously specified, the data has been factually tabulated with proper error ranges, and the representative graphs/diagrams appropriately presented to support the findings and results. Neuropsychological tests conducted for judgment of language and memory functions have taken into account the differences in educational and cultural background of the patients under investigation. Structural integrity of white matter has been studied with a modern and versatile facility. Regarding memory function, the left fornix is shown to be strongly associated with the function of immediate memory and has been found to be related to verbal delayed memory (VDM) and nonverbal delayed memory (NVDM). These findings are consistent with the findings presented by Kern et al.,[2] even though McDonald et al.[3] and Riley et al.[4] showed that the impairment of fornix plays a minor role in memory-related cognitive activity in TLE, but does not participate in language information processing.

The introduction to the topic is lucid and brings forth the salient features of the study. Results are reported with clarity, albeit with a bent towards quantitative analysis and abbreviated jargon. The discussion is succinct and highlights the importance of unexplored facets of neuroradiological diagnostic tools and software controlled studies in the evaluation of TLE.

The authors use an unconventional methodology but fail to explain their motivation for such a line of approach. The “why and how” of choosing this approach needs to be substantiated with experiment-based justifications. Winston [5] and Abhinav et al.[6] state that the standard DTI has a low spatial resolution relative to the underlying white matter structure. The voxel size is typically 2–3 mm, and the tensor model assumes that all fibres within a voxel are well-described by a single orientation estimate. In reality, a single voxel is likely to include multiple fibre tracts with unique orientations, and therefore, DTI is not well-equipped to resolve crossing fibres. Mean diffusivity and fractional anisotropy measurements of each fibre tract and their correlation with verbal fluency and recent/delayed memory need to be further verified with readings on overlapping/excess fibres. The study of white matter is largely an unchartered territory in the domain of cognitive functions. Advanced diffusion measures such as the ball-and-stick model, diffusion kurtosis imaging (DKI), and restriction spectrum imaging (RSI) exist for measuring network pathology associated with neurosurgical populations and neurodegenerative diseases.[6] Fibre tracking is not amenable to a clear solution of the issue.

The target group need not be restricted to those with a negative MRI but may be enlarged to include those epileptics who show a positive MRI scan. In fact, fresh cases, who have not yet initiated any treatment protocol, could serve as the best test cases for a random study. The authors have taken a relatively small and conforming group of 26 as target, and 17, as control participants. Statistical tests of analysis on groups of this size often lead to erroneous and misleading interpretations. Authors should be aware of such “statistical truths” that could potentially lead to false conclusions. Large and diversified subjects and long-term study/follow-up are essential to understand the underlying complexities.

 
  References Top

1.
Narenmandula B, Zhou X, Li Y, Tu D, Bao Y, Zheng R, Xu H. Effects of white matter microstructure lesions on language and memory function in magnetic resonance imaging-negative temporal lobe epilepsy determined by diffusion tensor imaging. Neurol India 2016;64:1233-42.  Back to cited text no. 1
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2.
Kern KC, Ekstrom AD, Suthana NA, Giesser BS, Montag M, Arshanapalli A, et al. Fornix damage limits verbal memory functional compensation in multiple sclerosis. Neuroimage 2012;59:2932-40.  Back to cited text no. 2
    
3.
McDonald CR, Ahmadi ME, Hagler DJ, Tecoma ES, Iragui VJ, Gharapetian L, et al. Diffusion tensor imaging correlates of memory and language impairments in temporal lobe epilepsy. Neurology 2008;71:1869-76.  Back to cited text no. 3
    
4.
Riley JD, Franklin DL, Choi V, Kim RC, Binder DK, Cramer SC, et al. Altered white matter integrity in temporal lobe epilepsy: Association with cognitive and clinical profiles. Epilepsia 2010;51:536-45.  Back to cited text no. 4
    
5.
Winston GP. The physical and biological basis of quantitative parameters derived from diffusion MRI. Quant Imaging Med Surg 2012;2:254-65.  Back to cited text no. 5
    
6.
Abhinav K, Yeh FC, Pathak S, Suski V, Lacomis D, Friedlander RM, et al. Advanced diffusion MRI fiber tracking in neurosurgical and neurodegenerative disorders and neuroanatomical studies: A review. Biochim Biophys Acta 2014;1842:2286-97.  Back to cited text no. 6
    




 

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