Ann Clin Neurophysiol.  2022;24(2):73-78. 10.14253/acn.2022.24.2.73.

Abnormal spontaneous electromyographic activity in myasthenia gravis causing a diagnostic confusion: a case report and literature review

• Kim S
• Kang M
• Park JS
• Seok HY

• KMID: 2535722
• DOI: http://doi.org/10.14253/acn.2022.24.2.73

Abstract

Some cases of myasthenia gravis (MG) with abnormal spontaneous activity (ASA) in needle electromyography (EMG) have been reported, but the associated clinical characteristics remain to be fully elucidated. We report the case of a 36-year-old male with MG in whom ASA was observed. This study highlights that ASA may appear in needle EMG in patients with severe MG who predominantly have bulbar and/or respiratory involvement. Care is needed because this often accompanies myopathic features and can be misdiagnosed as myopathy.

Keyword

Myasthenia gravis; Electromyography; Spontaneous activity

Figure

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  Fig. 1. Electrophysiological findings for the patient. (A) Needle electromyography revealed fibrillation potentials and/or positive sharp waves in the right genioglossus, flexor carpi radialis, peroneus longus, and cervical paraspinal muscles, and myopathic motor unit potentials in the right genioglossus muscle. Repetitive nerve stimulation at 5 Hz elicited decremental responses in the orbicularis oculi (B, -39% at rest and -35.6% postexercise) and abductor digiti minimi (C, -33.9% at rest and -42.6% postexercise). NL, normal.

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