J Clin Neurol.  2013 Jan;9(1):32-35. 10.3988/jcn.2013.9.1.32.

Decremental Responses to Repetitive Nerve Stimulation in X-Linked Bulbospinal Muscular Atrophy

Affiliations
  • 1Department of Neurology, Kwandong University College of Medicine, Myongji Hospital, Goyang, Korea.
  • 2Department of Neurology, Ewha Womans University School of Medicine, Seoul, Korea.
  • 3Department of Neurology, Yonsei University School of Medicine, Seoul, Korea.
  • 4Sunwoo & Cho Neurology Clinic, Seoul, Korea. sunwooin@yuhs.ac

Abstract

BACKGROUND AND PURPOSE
X-linked bulbospinal muscular atrophy (X-BSMA) is characterized by bulbar and spinal muscular weakness and fasciculations. Although X-BSMA is a motor neuronopathy, there are several reports of myasthenic symptoms or decremental responses to repetitive nerve stimulation (RNS). We report the results of applying the RNS test to 15 patients among 41 with genetically confirmed X-BSMA; these 15 patients complained of fatigue, ease of becoming tired, or early muscular exhaustion.
METHODS
The 3-Hz RNS test was performed on the trapezius, nasalis, orbicularis oculi, flexor carpi ulnaris, and abductor digiti quinti muscles. A decrement greater than 10% was considered abnormal. Additionally, a pharmacologic response to neostigmine was identified in three patients.
RESULTS
A significant decrement was observed in 67% of patients, and was most common in the trapezius muscle (nine cases). The decrement of the trapezius muscle response ranged from 15.9% to 36.9%. The decrement was inversely correlated with the amplitude of compound muscle action potentials at rest. Neostigmine injection markedly improved the decrement in three patients, who showed noticeable decremental responses to 3-Hz RNS.
CONCLUSIONS
This study shows that myasthenic symptoms and abnormal decremental responses to low-rate RNS are common in X-BSMA.

Keyword

bulbospinal; muscular atrophy; myasthenia gravis; motor neuron disease; neuromuscular junction

MeSH Terms

Action Potentials
Bulbo-Spinal Atrophy, X-Linked
Fasciculation
Fatigue
Humans
Motor Neuron Disease
Muscle Weakness
Muscles
Muscular Atrophy
Myasthenia Gravis
Neostigmine
Neuromuscular Junction
Neostigmine

Figure

  • Fig. 1 Spearman-correlation-coefficient-based comparison between amplitudes of compound muscle action potentials (CMAPs) at rest and decremental responses to 3-Hz repetitive stimulation recorded for the trapezius muscle.

  • Fig. 2 Changes in responses to 3-Hz repetitive nerve stimulation of case 8 before and after injecting 1.5 mg of neostigmine.


Cited by  2 articles

Clinical and Electrophysiologic Responses to Acetylcholinesterase Inhibitors in MuSK-Antibody-Positive Myasthenia Gravis: Evidence for Cholinergic Neuromuscular Hyperactivity
Ha Young Shin, Hyung Jun Park, Hyo Eun Lee, Young-Chul Choi, Seung Min Kim
J Clin Neurol. 2014;10(2):119-124.    doi: 10.3988/jcn.2014.10.2.119.

Clinical Significance of Repetitive Compound Muscle Action Potentials in Patients with Myasthenia Gravis: A Predictor for Cholinergic Side Effects of Acetylcholinesterase Inhibitors
Hyo Eun Lee, Yool-hee Kim, Seung Min Kim, Ha Young Shin
J Clin Neurol. 2016;12(4):482-488.    doi: 10.3988/jcn.2016.12.4.482.


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