Exp Neurobiol.  2014 Sep;23(3):253-257. 10.5607/en.2014.23.3.253.

Comparison between Flail Arm Syndrome and Upper Limb Onset Amyotrophic Lateral Sclerosis: Clinical Features and Electromyographic Findings

  • 1Department of Neurology, Inha University Hospital, Incheon 400-711, Korea.
  • 2Department of Neurology, College of Medicine, Jeju National University, Jeju 690-767, Korea.
  • 3Department of Neurology, Seoul National University Hospital, College of Medicine, Seoul 110-744, Korea. jjsaint@snu.ac.kr


Flail arm syndrome (FAS), an atypical presentation of amyotrophic lateral sclerosis (ALS), is characterized by progressive, predominantly proximal, weakness of upper limbs, without involvement of the lower limb, bulbar, or respiratory muscles. When encountering a patient who presents with this symptomatic profile, possible diagnoses include upper limb onset ALS (UL-ALS), and FAS. The lack of information regarding FAS may make differential diagnosis between FAS and UL-ALS difficult in clinical settings. The aim of this study was to compare clinical and electromyographic findings from patients diagnosed with FAS with those from patients diagnosed with UL-ALS. To accomplish this, 18 patients with FAS and 56 patients with UL-ALS were examined. Significant differences were observed between the 2 groups pertaining to the rate of fasciculation, patterns of predominantly affected muscles, and the Medical Research Council scale of the weakest muscle. The presence of upper motor neuron signs and lower motor neuron involvement evidenced through electromyography showed no significant between-group differences.


flail arm syndrome; amyotrophic lateral sclerosis; brachial amyotrophic diplegia; electromyography; motor neuron disease
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