Decremental Responses to Repetitive Nerve Stimulation in X-Linked Bulbospinal Muscular Atrophy |
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| Authors: | Jee Young Kim Kee Duk Park Seung-Min Kim Il Nam Sunwoo |
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| Affiliation: | aDepartment of Neurology, Kwandong University College of Medicine, Myongji Hospital, Goyang, Korea.;bDepartment of Neurology, Ewha Womans University School of Medicine, Seoul, Korea.;cDepartment of Neurology, Yonsei University School of Medicine, Seoul, Korea.;dSunwoo & Cho Neurology Clinic, Seoul, Korea. |
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| Abstract: | Background and PurposeX-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.MethodsThe 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.ResultsA 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.ConclusionsThis study shows that myasthenic symptoms and abnormal decremental responses to low-rate RNS are common in X-BSMA. |
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| Keywords: | bulbospinal muscular atrophy myasthenia gravis motor neuron disease neuromuscular junction |
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