Neurophysiological Differences between Flail Arm Syndrome and Amyotrophic Lateral Sclerosis.

Hecheng Yang,Mingsheng Liu,Jia Fang,Xiaoguang Li,Weidong Le,Liying Cui,Bo Cui

doi:10.1371/journal.pone.0127601

Abstract

There are many clinical features of flail arm syndrome (FAS) that are different from amyotrophic lateral sclerosis (ALS), suggesting they are probably different entities. Studies on electrophysiological differences between them are limited at present, and still inconclusive. Therefore, we aimed to find clinical and neurophysiological differences between FAS and ALS. Eighteen healthy control subjects, six FAS patients and forty-one ALS patients were recruited. The upper motor neuron signs (UMNS), split-hand index (SI), resting motor threshold (RMT), central motor conduction time (CMCT) were evaluated and compared. There was no obvious upper motor neuron signs in FAS. The SI and RMT level in FAS was similar to control subjects, but significantly lower than that of in ALS. Compared with control group, the RMT and SI in ALS group were both significantly increased to higher level. However, no significant difference of CMCT was found between any two of these three groups. The differences in clinical and neurophysiological findings between FAS and ALS, argue against they are the same disease entity. Since there was no obvious UMNS, no split-hand phenomenon, and no obvious changes of RMT and CMCT in FAS patients, the development of FAS might be probably not originated from motor cortex.

Highlights

Flail arm syndrome (FAS), called man-in-barrel syndrome, or brachial amyotrophic diplegia, is a slowly progressive sporadic motor neuron disorder, characterized by severe flaccid paralysis and muscle wasting in both arms symmetrically, while relatively sparing the legs and bulbar parts, and with few signs of upper motor neuron lesions[1]
In Amyotrophic lateral sclerosis (ALS) group, the ratio of female to male was 1:1.56 (16:25). There was another difference between FAS and ALS patients in the presence of upper motor neuron signs (UMNS)
We found that there was no significant difference of split-hand index (SI), resting motor threshold (RMT), central motor conduction time (CMCT) between FAS patients and control subjects

Summary

Introduction

Flail arm syndrome (FAS), called man-in-barrel syndrome, or brachial amyotrophic diplegia, is a slowly progressive sporadic motor neuron disorder, characterized by severe flaccid paralysis and muscle wasting in both arms symmetrically, while relatively sparing the legs and bulbar parts, and with few signs of upper motor neuron lesions[1]. Amyotrophic lateral sclerosis (ALS) is another degenerative motor neuron disorder, with progressive loss of both upper and lower motor neurons in motor cortex, spinal anterior horn cells and motor neurons in brain stem[2]. The relationship between FAS and ALS is still unclear. Some researchers argue this syndrome is a variant of ALS, while others believe that FAS is an independent entity[3,4,5]. There are several clinical characteristics of FAS that are very different from classical ALS, including

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