Needle electromyography abnormalities in the upper trapezius muscle in neuromuscular disorders

: Needle electromyography (EMG) abnormalities in the trapezius muscle (TM) can be seen in neuromuscular disorders. The aim was to determine the characteristics of needle EMG abnormalities observed in the TM in neuromuscular disorders.

The data of patients who applied to the Clinical Neurophysiology Laboratory of University of Health Sciences Adana City Training and Research Hospital between December 2018 and October 2021 were reviewed. Polio survivors, amyotrophic lateral sclerosis (ALS) patients, patients with sensorimotor polyneuropathy, patients with spinal cord lesions involving C2/C3/C4 segments, patients with spinal accessory nerve (SAN) lesions, neuralgic amyotrophy (NA) patients, and patients with myopathy were included. Needle EMG findings of the upper TM of the patients were analyzed. Positive sharp waves, fibrillation potentials, fasciculation potentials, myotonic discharges, and motor unit action potential (MUAP) changes were considered needle EMG abnormalities.

Eighty-one polio survivors, 23 ALS patients, 39 patients with sensorimotor polyneuropathy, 10 patients with cervical spinal lesions, eight NA patients, seven patients with SAN lesions, and three patients with myopathy were included in the study. Fifteen (65.2%) ALS patients, 18 (22.2%) polio survivors, three (30%) patients with cervical spinal lesions, two (5.1%) patients with sensorimotor neuropathy, one (12.5%) NA patient, seven (100%) patients with SAN lesions, and two (66.7%) patients with myopathies had at least one needle EMG abnormality in the TM. Fasciculation potentials in the TM were seen in 10 (43.5%) ALS patients. In four patients with SAN lesions and one polio survivor, MUAP could not be obtained from the TM.

There may be more frequent needle EMG abnormalities, particularly in ALS patients and patients with SAN lesions. Since the number of patients with myopathy included in this study was low, it is difficult to comment on the needle EMG features of the TM for these patients. In addition, this study indicated that fasciculation potentials in the TM are typical in ALS patients and that MUAP may not be obtained from the TM in patients with SAN lesions.