Split-hand phenomenon in amyotrophic lateral sclerosis: A motor unit number index study.
The split-hand phenomenon refers to preferential wasting of the thenar muscles with relative sparing of the hypothenar muscles in amyotrophic lateral sclerosis (ALS).



We compared the split-hand index (SI) calculated from the compound muscle action potential (CMAP; SICMAP ) with that calculated from the motor unit number index (MUNIX; SIMUNIX ). We performed MUNIX on the abductor policis brevis (APB), first dorsal interosseous (FDI), and abductor digiti minimi (ADM) muscles of 39 ALS patients and 40 age-matched, healthy controls. SI is derived by multiplying the CMAP (or MUNIX) recorded over the APB and FDI and dividing by the CMAP (or MUNIX) recorded over the ADM.



Receiver-operating characteristic curve analysis revealed good diagnostic accuracy for both indices, but better performance of SIMUNIX than SICMAP .



SIMUNIX and SICMAP were useful in differentiating ALS patients from healthy controls. SIMUNIX appears to be a better electrophysiological marker than SICMAP for the split-hand sign of ALS. Muscle Nerve 53: 885-888, 2016.
Department of Neurology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seoul, Republic of Korea.
Dong-Gun
DG
Kim
Department of Neurology, Seoul Metropolitan Government Boramae Medical Center, Seoul National University College of Medicine, Seoul, Republic of Korea.
Yoon-Ho
YH
Hong
Department of Neurology, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Republic of Korea.
Je-Young
JY
Shin
Department of Neurology, Gyeongsang National University Hospital, Jinju, Korea.
Kee Hong
KH
Park
Department of Neurology, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Republic of Korea.
Sung-Yeon
SY
Sohn
Department of Neurology, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Republic of Korea.
Kwang-Woo
KW
Lee
Department of Neurology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seoul, Republic of Korea.
Kyung Seok
KS
Park
Department of Neurology, Seoul Metropolitan Government Boramae Medical Center, Seoul National University College of Medicine, Seoul, Republic of Korea.
Jung-Joon
JJ
Sung
D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000150:complications* / Q000473:pathology*; D016022:Case-Control Studies; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006225:Hand / Q000294:innervation / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology / Q000503:physiopathology*; D012372:ROC Curve
MUNIX; amyotrophic lateral sclerosis; compound muscle action potential; motor unit number index; split hand; split index