Evaluation of corticospinal tracts in ALS with diffusion tensor MRI and brainstem stimulation.
OBJECTIVE
To assess corticospinal tract involvement in patients with amyotrophic lateral sclerosis (ALS) by correlating diffusion tensor imaging (DTI) measures with intra- and extracranial central motor conduction time (CMCT) and clinical features of the patients.


METHODS
We investigated 31 patients with ALS and 31 normal volunteers by DTI and measured fractional anisotropy (FA) within the corticospinal tracts and in the extramotor white matter. We measured CMCT for the first dorsal interosseous muscle and segmented it into cortical-brainstem (CTX-BS CT) and brainstem-cervical root (BS-CV CT) conduction times by magnetic brainstem stimulation at the foramen magnum level. Clinical status of each patient was evaluated with the ALS Functional Rating Scale-Revised (ALSFRS-R) and upper motor neuron (UMN) score devised for this study.


RESULTS
We found a significant decrease of mean FA in all regions of the corticospinal tracts in patients with ALS as compared with controls. We found that FA along the corticospinal tract decreased significantly with higher UMN scores. There was no significant correlation between FA and ALSFRS-R, to which both upper and lower motoneuron involvements contribute. FA showed a significant correlation with the intracranial part of the central motor conduction (CTX-BS CT) but not with the extracranial conduction time.


CONCLUSIONS
Fractional anisotropy reflects functional abnormality of intracranial corticospinal tracts and can be used for objective evaluation of upper motor neuron impairment in amyotrophic lateral sclerosis.
Iwata
N K
NK
Department of Neurology, Division of Neuroscience, Graduate School of Medicine, University of Tokyo, Japan. iwatan@ninds.nih.gov
Aoki
S
S
Okabe
S
S
Arai
N
N
Terao
Y
Y
Kwak
S
S
Abe
O
O
Kanazawa
I
I
Tsuji
S
S
Ugawa
Y
Y
D000328:Adult; D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000175:diagnosis* / Q000503:physiopathology*; D016880:Anisotropy; D001933:Brain Stem / Q000503:physiopathology; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D004558:Electric Stimulation; D004568:Electrodiagnosis / Q000379:methods*; D006801:Humans; D008875:Middle Aged; D009044:Motor Cortex / Q000473:pathology / Q000503:physiopathology; D009046:Motor Neurons / Q000473:pathology; D009431:Neural Conduction / Q000502:physiology; D011237:Predictive Value of Tests; D011712:Pyramidal Tracts / Q000473:pathology* / Q000503:physiopathology*; D011930:Reaction Time; D013997:Time Factors