Flail Arm Syndrome

1. A D E W I J A Y A , M D
D E C E M B E R 2 0 2 3
Flail Arm Syndrome

2. Introduction
 Flail Arm Syndrome (FAS) is an atypical form of
Motor Neuron Disease (MND)
 Synonim: Vulpian-Bernhardt syndrome, man-in-the
barrel syndrome, or brachial amyotrophic diplegia
Wijesekera LC, Mathers S, Talman P, Galtrey C, Parkinson MH, Ganesalingam J, Willey E, Ampong MA, Ellis CM, Shaw CE, Al-Chalabi A, Leigh PN (2009) Natural history and clinical features
of the flail arm and flail leg ALS variants. Neurology 72(12):1087–1094. doi:10.1212/01.wnl.0000345041.83406.a2 Sasaki S, Iwata M (1999) Atypical form of amyotrophic lateral sclerosis. J
Neurol Neurosurg Psychiatry 66(5):581–585
Katz JS, Wolfe GI, Andersson PB, Saperstein DS, Elliott JL, Nations SP, Bryan WW, Barohn RJ (1999) Brachial amyotrophic diplegia: a slowly progressive motor neuron disorder. Neurology
53(5):1071–1076

3. Clinical Presentation
 Predominantly proximal, progressive and symmetric
wasting and paresis of the upper limb muscles, while
lower limbs and bulbar muscles are spared
Higher share of male patients than ALS (m:f = 4:1)
Younger age of onset than ALS (mean age = 55 years)
Prolonged survival compared to ALS (mean: 20
months)
First manifestation most frequently distal and at the
dominant side
Couratier P, Truong C, Khalil M, Deviere F, Vallat JM (2000) Clinical features of flail arm syndrome. Muscle Nerve 23(4):646–648
Hübers A, Hildebrandt V, Petri S, Kollewe K, Hermann A, Storch A, Hanisch F, Zierz S, Rosenbohm A, Ludolph AC, Dorst J. Clinical features and differential diagnosis of flail arm
syndrome. Journal of neurology. 2016 Feb;263:390-5.

4. Diagnosis
Wijesekera LC, Mathers S, Talman P, Galtrey C, Parkinson MH, Ganesalingam J, Willey E, Ampong MA, Ellis CM, Shaw CE, Al-Chalabi A. Natural history and clinical
features of the flail arm and flail leg ALS variants. Neurology. 2009 Mar 24;72(12):1087-94.

5. Diagnosis
 Clinical
 Electrodiagnostic study
 Genetic molecular investigation
GAMEZ J, CERVERA C, CODINA A. Flail arm syndrome or VulpianBernhart’s form of amyotrophic lateral sclerosis. Journal of Neurology, Neurosurgery & Psychiatry. 1999 Aug 1;67(2):258-.

6. Electrodiagnostic Study
 Similar feature to ALS
 Reduced split hand index in ALS
 Split hand index:
To calculate the SHI is by multiplying the CMAP
amplitude recorded over the APB and FDI muscles,
and dividing this product by the CMAP amplitude
recorded over the ADM muscle, as follows:
SHI = APB (CMAP) × FDI (CMAP)/ADM CMAP
Yang H, Liu M, Li X, Cui B, Fang J, Cui L. Neurophysiological differences between flail arm syndrome and amyotrophic lateral sclerosis. PloS one. 2015 Jun 9;10(6):e0127601.
LIU F, SONG C, LIU H, ZHANG M, FENG S, LI L. The clinical and electrophysiological characteristics of flail arm syndrome. Chinese Journal of Physical Medicine and Rehabilitation. 2021:21-4.

7. Differential Diagnosis
 Multifocal Motor Neuropathy
 Spinal Muscular Atrophy
 Carpal Tunnel Syndrome
 Herniated disc
Hübers A, Hildebrandt V, Petri S, Kollewe K, Hermann A, Storch A, Hanisch F, Zierz S, Rosenbohm A, Ludolph AC, Dorst J. Clinical features and differential diagnosis of flail arm
syndrome. Journal of neurology. 2016 Feb;263:390-5.

8. Treatment
 No cure
 Supportive / symptomatic treatment

9. Summary
 FAS is an atypical form of Motor Neuron Disease
 Predominantly proximal, progressive and symmetric
wasting and paresis of the upper limb muscles
 Diagnosis: Clinical, electrodiagnostic, genetic
 No cure
 Prognosis better than ALS

10. THANK YOU