RT Journal Article
SR Electronic
T1 Split hand syndrome in amyotrophic lateral sclerosis: different excitability changes in the thenar and hypothenar motor axons
JF Journal of Neurology, Neurosurgery & Psychiatry
JO J Neurol Neurosurg Psychiatry
FD BMJ Publishing Group Ltd
SP 969
OP 972
DO 10.1136/jnnp-2012-304109
VO 84
IS 9
A1 Kazumoto Shibuya
A1 Sonoko Misawa
A1 Saiko Nasu
A1 Yukari Sekiguchi
A1 Satsuki Mitsuma
A1 Minako Beppu
A1 Shigeki Ohmori
A1 Yuta Iwai
A1 Shoichi Ito
A1 Kazuaki Kanai
A1 Yasunori Sato
A1 Satoshi Kuwabara
YR 2013
UL http://jnnp.bmj.com/content/84/9/969.abstract
AB Background In amyotrophic lateral sclerosis (ALS), muscle wasting preferentially affects the abductor pollicis brevis (APB) and first dorsal interosseous over the abductor digit minimi (ADM), and this is termed ‘split hand’. Previous axonal excitability studies have suggested increased nodal persistent sodium current and reduced potassium current in motor axons in ALS, but the extent of excitability changes in APB and ADM axons in ALS has never been compared. Objective To elucidate the peripheral axonal pathophysiology of split hand. Methods In both APB and ADM motor axons of 21 patients with ALS and 17 age-matched normal controls, threshold tracking was used to measure excitability indices such as strength-duration time constant (SDTC; a measure of persistent sodium current) and threshold electrotonus. Results In normal controls, SDTC was significantly longer for APB than ADM axons, suggesting that axonal excitability is physiologically higher in APB axons. Compared with normal controls, patients with ALS had longer SDTC and greater threshold changes in depolarising threshold electrotonus in both APB and ADM axons. Furthermore, the difference in extent of SDTC prolongation between normal subjects and patients with ALS was greater in APB than ADM axons. Conclusions APB axons have physiologically higher excitability than ADM axons, and, in ALS, the hyperexcitability is more prominent in APB axons. Although cortical mechanisms would also be involved, more prominent hyperexcitability of APB axons may contribute to development of split hand, and the altered axonal properties are possibly associated with motor neuronal death in ALS.