Post-Transplant Pain and Paralysis: Neurologic Amyotrophy As an Atypical Cause of Shoulder Dysfunction Following Hematopoietic Stem Cell Transplant

Introduction:

Neuralgic amyotrophy (NA), also known as Parsonage-Turner Syndrome, brachial neuritis, or idiopathic brachial plexopathy, is a rare inflammatory peripheral nervous system disorder affecting the brachial plexus, typically presenting as sudden and abrupt unilateral shoulder pain followed by progressive painless weakness and occasionally reflex and sensory abnormalities. Diagnosis is clinical - based on history and detailed neuromuscular physical examination. Electrodiagnostic studies (EDX) and advanced imaging are supportive to confirm diagnosis and exclude alternative etiologies. While the pathogenesis is not entirely understood, the idiopathic form is thought to be secondary to immune or vascular mediated effects with only a few case reports after hematopoietic stem cell transplantation (HCT). Given under recognition and misdiagnosis, a high degree of suspicion is necessary in patients developing acute onset of shoulder pain after HCT. While no curative treatment is available, early diagnosis will result in appropriate management, patient education, pain control, and timely focused rehabilitation.

Methods:

We retrospectively collected demographics, HCT details, clinical characteristics, imaging studies, and EDX on patients with acute shoulder pain post-HCT at a single institution. Descriptive statistics were utilized to summarize the collected data.

Results:

Between 8/2020 -7/2022, nine patients (44% male, median age 60 years) were diagnosed with NA following autologous (n=4, for multiple myeloma (n=2), non-Hodgkin lymphoma (n=1), or germ cell tumor (n=1)) or allogeneic HCT (n=5, for myelodysplastic syndrome (n=3) and acute myelogenous leukemia (n=2)). Each patient acutely developed severe shoulder pain at a median of 9 days (range 1-21) mean. Shoulder 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 one patient developed sensory deficits in the affected upper extremity. Shoulder 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 showed periscapular muscle edema, atrophy and enhancement in six patients. These signal abnormalities were observed in varying distributions including supraspinatus, infraspinatus, deltoid, teres minor, serratus anterior and intercostals (Figure 1). Of the 6 patients who had EDX, findings were consistent with NA in 5 patients (axillary neuropathy in 2 patients, upper trunk plexopathy in 1 patient, bilateral posterior cord plexopathy in 1 patient and diffuse bilateral brachial plexopathy in 1 patient). All patients were treated with pain medications and received optimal rehabilitative care including consult with physical medicine and rehabilitation physicians and physical and occupational therapy. Upon long term follow up (>1 year), three patients experienced full or near-full resolution of symptoms, four patients partially recovered, and two patients had little to no improvement of their neurological symptoms.

Conclusion:

Patients undergoing HCT are susceptible to neurological insults, potentially driven by immune-mediated mechanisms. In individuals experiencing acute shoulder pain accompanied by neurological symptoms early post-HCT, it is important to maintain a high level of suspicion for the diagnosis of NA. A timely diagnosis is essential to facilitate early intervention and ensure optimal functional recovery. MRI of the shoulder and/or brachial plexus and EDX are valuable diagnostic tools for assessing the presence and distribution of neuromuscular involvement. While recovery is possible, comprehensive long-term follow-up is necessary to ascertain the extent of symptom resolution and functional restoration.