Abnormal spontaneous activity in primary myopathic disorders.

Area of Science:

• Neurology
• Clinical Electrophysiology
• Muscle Diseases

Background:

• Reproducible non-insertional spontaneous activity (SA), excluding endplate potentials, signifies abnormality on electromyography.
• SA is a crucial diagnostic finding in neuromuscular disorders.

Purpose of the Study:

• To analyze the occurrence and distribution of abnormal SA in patients with genetically confirmed myopathies.
• To correlate specific SA findings with different types of myopathies.

Main Methods:

• Retrospective analysis of 151 patients with genetically confirmed myopathies.
• Evaluation of the types and frequencies of abnormal spontaneous activity, including complex repetitive discharges (CRDs), fibrillation potentials (fibs), and positive sharp waves (PSWs).

Main Results:

• Abnormal SA was most frequent in centronuclear myopathy (CNM) and desminopathy.
• Complex repetitive discharges (CRDs) were more prevalent than fibrillation potentials (fibs)/positive sharp waves (PSWs) in CNM and limb-girdle muscular dystrophy type 2A (LGMD-2A).
• Fibs/PSWs were more common in desminopathy and facioscapulohumeral dystrophy (FSHD), with varying frequencies of abnormal SA across different myopathies.

Conclusions:

• Abnormal SA is likely more common in myopathies with structural muscle fiber changes.
• Screening for SA can be a valuable diagnostic aid for non-myotonic myopathies.