Neuralgic Amyotrophy As an Atypical Cause of Acute Shoulder Pain and Paralysis Following Hematopoietic Stem Cell Transplant

Introduction Neuralgic amyotrophy (NA) is a rare inflammatory brachial plexopathy; typically manifesting as a sudden onset of shoulder pain with subsequent painless weakness. Diagnosis primarily relies on clinical history and neuromuscular examination, along with electrodiagnostic studies (EDX) and advanced imaging. The idiopathic form is believed to stem from immune or vascular mediated effects. A limited number of case reports have documented its occurrence after hematopoietic stem cell transplantation (HSCT). Methods A retrospective review was conducted to collect demographics, HSCT details, clinical characteristics, and diagnostic studies in patients with acute shoulder pain post-HSCT at a single institution. Descriptive statistics were utilized to summarize the collected data. Results Between 08/2020 – 07/2022, nine patients (44% male, median age 60 years) were diagnosed with NA following autologous (n=4; multiple myeloma (n=2), non-Hodgkin lymphoma (n=1), and germ cell tumor (n=1)) or allogeneic HSCT (n=5, for myelodysplastic syndrome (n=3) and acute myelogenous leukemia (n=2)). Each patient developed acute shoulder pain at a median of 9 days (range 1-21). Pain was bilateral in 3 patients. Neurological weakness involving the shoulder(s) was observed on average 5.1 days after pain onset (range 1-15 days). All but 1 patient developed associated sensory deficits. Pain subsided after a median of 23 days (range 8-40 days). MRI of the shoulder and/or brachial plexus was performed in all patients and in 6 patients showed periscapular muscle edema, atrophy, and enhancement (involving the supraspinatus, infraspinatus, deltoid, teres minor, serratus anterior and intercostals (Figure 1). 6 patients underwent EDX with findings consistent with NA in 5 patients. All patients received optimal pain and rehabilitative management. Upon long term follow up, 3 patients experienced full/near-full resolution of symptoms, 4 patients partially recovered, and 2 patients had little/no improvement of their neurological symptoms. Conclusion It is important to maintain a high degree of suspicion for NA in patients experiencing acute shoulder pain accompanied by neurological symptoms early post-HSCT. A timely diagnosis facilitates optimal functional recovery.