Ultrasound Evaluation of Post Covid-19 Neuralgic Amyotrophy: A Case Report

The Ohio State University

CASE DESCRIPTION: A 33-year-old male presented with 10 months of chronic shoulder pain with flexion. Two weeks prior to the onset of his symptoms, he had a significant flu-like illness thought to be COVID-19. He had severe pain and immobility of the shoulder at onset. This improved within a few days to pain primarily with activity. Magnetic resonance imaging (MRI) of the shoulder was unremarkable and an electrodiagnostic evaluation performed at another institution reported an incomplete left suprascapular neuropathy but no evidence of long thoracic neuropathy. On examination, he had profound medial scapular winging with wall pushup. He has been involved in extensive physical therapy that had helped his mobility but not pain. He was referred to the clinic for a high-frequency ultrasound evaluation.

ASSESSMENT AND RESULTS: High-frequency ultrasound showed marked atrophy and hyperechoic signal change in the left serratus anterior and supraspinatus. There was also diffuse enlargement of both the long thoracic and the suprascapular nerves, but normal appearance of the remainder of the brachial plexus

DISCUSSION: The clinical history and sonographic pattern of diffuse enlargement of two distinct nerves about the shoulder with no focal signs of entrapment support the likelihood of neuralgic amyotrophy (aka Parsonage-Turner syndrome). Diagnostic confusion was created by the false negative electrodiagnostic study in this case, despite clear weakness noted clinically. This reflects the technical challenge of demonstrating electromyographic abnormalities in a severely atrophied serratus anterior, but the potential value of inspection with ultrasound.

CONCLUSION: High frequency ultrasound can be used in conjunction with electrodiagnosis to localize and characterize multi-focal neuropathies and is helpful with complicated presentations of neuralgic amyotrophy.