The Motor Unit Number Index of Subclinical Abnormality in Amyotrophic Lateral Sclerosis.
OBJECTIVE
Diagnosis of amyotrophic lateral sclerosis (ALS) at an early stage is challenging, thus making the enrollment of these patients in clinical trials infeasible. In this study, we investigated the potential usability of motor unit number index (MUNIX) to detect denervation of clinically intact muscles of ALS patients.


METHODS
Thirty-two first dorsal interosseous muscles of 26 ALS patients were evaluated with both MUNIX and needle electromyography.


RESULTS
The mean MUNIX value of first dorsal interosseous muscles was 131 in the control group, whereas it was 48, 34, 15, and 8 for Medical Research Council scales of 5, 4, 3, and 2, respectively, in the ALS patients. The optimal cutoff point gave a sensitivity of 0.89 and a specificity of 1.0. Among 9 intact first dorsal interosseous muscles of the ALS patients, 8 showed MUNIX values below the cutoff point, whereas only 2 first dorsal interosseous muscles showed denervation on needle electromyography.


CONCLUSIONS
MUNIX could serve as a sensitive technique to detect denervation of clinically intact muscles of ALS patients.
*Department of Neurology, Osaka General Medical Center, Osaka, Japan; †Osaka College of High Technology, Osaka, Japan; ‡Department of Neurology, Osaka University Graduate School of Medicine, Osaka, Japan; §Department of Neurology, Shizuoka Institute of Epilepsy and Neurological Disorders, Shizuoka, Japan; and ‖Department of Neurology, Toneyama National Hospital, Osaka, Japan.
Kei
K
Fukada
Toyoko
T
Matsui
Mitsuru
M
Furuta
Daisuke
D
Hirozawa
Misa
M
Matsui
Yuta
Y
Kajiyama
Mikito
M
Shimizu
Makoto
M
Kinoshita
Hideki
H
Mochizuki
Jin-Ichi
JI
Sawada
Takanori
T
Hazama
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000690:Amyotrophic Lateral Sclerosis / Q000175:diagnosis; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation* / Q000503:physiopathology*; D009431:Neural Conduction / Q000502:physiology