326 - Idiopathic Long Thoracic Nerve Palsy- A Case Report

Thursday, February 22, 2024

5:00 PM – 6:30 PM EDT

Presenting Author(s)

CS

Christian S. Saunders, BA

Medical Student
University of Texas Medical Branch
Galveston, Texas, United States

Co-Author(s)

MC

Merrit Crump, MD

Resident Physician
TTUHSC PM&R
Lubbock, Texas, United States
JC

Joel R. Campbell, MD

Orthopaedic surgeon
Lubbock Sports Medicine
Lubbock, Texas, United States
John W. Norbury, MD

Division Chief and Residency Program Director
TTUHSC
Lubbock, Texas, United States

Case Diagnosis: Idiopathic Long Thoracic Nerve Palsy

Case Description: A 51-year-old male presented to an electrodiagnostic (EDX) clinic with a one-year history of right upper back weakness and diminished right shoulder range of motion. He reported gradually worsening positional numbness and tingling when lying on his right side and pain when raising objects above his head. He does not recall any inciting injury. In late 2020, he experienced a flu-like illness suspected to be COVID-19. Physical exam was significant for visible and palpable right serratus anterior atrophy, right shoulder abduction limited to 100° due to pain and medial scapular winging on serratus anterior strength testing. Electrodiagnostic study did not demonstrate evidence of right upper extremity plexopathy, mononeuropathy, or polyneuropathy. Neuromuscular Ultrasound (NMUS) evaluation of the right serratus anterior demonstrated decreased muscle thickness and hyperechogenicity in comparison to the left side.

Discussions: Anecdotal evidence suggests that isolated idiopathic mononeuropathies became more common during the COVID-19 pandemic, and long thoracic palsies have been described following COVID-19 vaccination. Isolated scapular winging from a long thoracic palsy is an exceedingly rare diagnosis in the absence of trauma, neuralgic amyotrophy, or other clear etiology. Direct EDX evaluation of the long thoracic nerve is anatomically challenging in the presence of significant serratus anterior atrophy. NMUS can easily distinguish mononeuropathy from a more generalized neurological condition.

Conclusions: NMUS is a valuable adjuvant to the EDX examination and can help establish the diagnosis when atrophy of the serratus anterior makes EMG difficult and prone to pneumothorax. This case demonstrates the ability of NMUS to establish long thoracic nerve palsy while excluding a more generalized neuromuscular process.