Post-Transplant Pain and Paralysis: Neurologic Amyotrophy as an Atypical Cause of Shoulder Dysfunction Following...

Neuralgic amyotrophy (NA), also known as Parsonage-Turner syndrome, brachial neuritis, and idiopathic brachial plexopathy, is a rare and potentially debilitating peripheral nerve disorder characterized by acute-onset shoulder pain followed by progressive motor deficits. It is often under-recognized, with an estimated incidence of 1 to 3 per 100,000 annually, though some studies suggest the actual prevalence may be significantly higher. The condition typically progresses through three phases, an acute painful phase, a phase of weakness, and a recovery phase, with sensory disturbances common in addition to motor weakness. The exact pathogenesis of NA remains unclear, though it is thought to involve a combination of genetic, environmental, and immunological factors. While neurologic complications following hematopoietic stem cell transplantation (HSCT), such as neuropathies and myopathies, have been documented, NA remains exceedingly rare in this context, with only a few reported cases. The pathophysiology in HSCT patients is hypothesized to involve immune dysregulation, graft-versus-host disease (GvHD), infection, and the effects of immunosuppressive therapy. Diagnosis is primarily clinical, supported by electrodiagnostic studies and MRI, though no laboratory markers exist. The management of NA is largely supportive and multimodal, focusing on pain control and rehabilitation.

The objective of this study was to describe the characteristics, clinical course, and outcomes of patients admitted for HSCT who were subsequently diagnosed with NA.

This retrospective case series from a single institution examined nine (N = 9) patients who developed acute shoulder pain following HSCT. We collected data on demographics, transplant details, clinical features, MRI findings, and electrodiagnostic studies, summarized using descriptive statistics. The diagnosis of neurologic amyotrophy was based on clinical presentation and corroborated by imaging and electrodiagnostic results. Long-term follow-up was assessed to evaluate symptom recovery.

Between August 2020 and July 2022, nine patients (44% male, median age 60) were diagnosed with NA following autologous (n = 4) or allogeneic (n = 5) HSCT. The onset of severe shoulder pain occurred at a median of 9 days post-transplant (range 1-21 days), with the majority of patients experiencing unilateral pain, predominantly affecting the right shoulder (55%). Neurologic weakness developed on average 5.1 days after pain onset, and sensory deficits were observed in all but one patient. MRI findings revealed muscle edema, atrophy, and enhancement in six patients, while electromyography confirmed NA in five. Due to the small sample size, statistical analyses, including p-values, confidence intervals, and trend comparisons, were not performed, and thus no conclusions can be drawn regarding associations between variables such as early onset and worse outcomes. Shoulder pain resolved after a median of 23 days (range 8-40 days). Long-term follow-up (>1 year) showed that three patients achieved full or near-full recovery, four partially recovered, and two showed minimal improvement. Conclusions: NA should be highly suspected in patients with acute shoulder pain and neurologic symptoms post-HSCT. To improve diagnostic accuracy and clinical outcomes, we recommend enhanced clinician awareness, the implementation of targeted diagnostic protocols (such as MRI and electrodiagnostic studies), and the establishment of standardized long-term follow-up protocols.