Evaluation of White Matter Tracts Fractional Anisotropy Using Tract-Based Spatial Statistics and Its correlation with Amyotrophic Lateral Sclerosis Functional Rating Scale Score in Patients with Motor Neuron Disease.
Amutha Bharathi Mohan, Subathra Adithan, Sunil Narayan, Nagarajan Krishnan, Donna MathewsAim: To identify white matter tracts that have reduced fractional anisotropy (FA) in motor neuron disease (MND) patients using tract-based spatial statistics and to correlate FA values with Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R) score.
Methods: DTI (20 gradient directions, b -value 1,000) in 15 MND patients (10 men and 5 women; mean age: 46.5 ± 16.5 years; 11 amyotrophic lateral scleroses, 2 monomelic amyotrophy, 1 progressive muscular atrophy, 1 bulbar ALS) and 15 age- and sex-matched controls was performed in a 1.5 Tesla MRI machine. The data set from each subject were post-processed using FSL downloaded from the FMRIB Software Library, Oxford, United Kingdom (http://www.fmrib.ox.ac.uk/fsl). The statistical permutation tool “randomize” with 5,000 permutations was used to identify voxels that were different between the patient data set and the control data set. The mean FA values of these voxels were obtained separately for each tract as per the “JHU white-matter tractography atlas.” SPSS was used to look to correlate tract-wise mean FA value with ALSFRS-R score.
Results: We found clusters of reduced FA values were found in multiple tracts in the brain of patients with MND. Receiver operating characteristic curves plotted for individual tracts, showed that FA values at bilateral corticospinal tract, bilateral anterior thalamic radiation, bilateral uncinate fasciculus, and right superior longitudinal fasciculus best discriminated MND brains from normal brains (area under the curve > 0.8, p < 0.01). However, FA values did not correlate with the ALFRS-R severity score.
Conclusion: In patients with motor neuron disease, alteration in white matter integrity is present not only in motor tracts but also in several nonmotor association tracts indicating probable involvement of nonmotor neurons and tracts also in the pathological processes.