Complex Regional Pain Syndrome-Not Otherwise Specified Following Minor Upper Limb Trauma: A Case Report

Complex regional pain syndrome (CRPS) is a chronic pain condition characterized by disproportionate regional pain with sensory, autonomic, and motor abnormalities. While the Budapest criteria are widely accepted for diagnosis, some patients present with incomplete or atypical features and fail to meet full diagnostic thresholds. These cases are classified as CRPS-not otherwise specified (CRPS-NOS). Increasing evidence suggests that altered central pain processing (nociplastic pain) plays a key role in such atypical CRPS phenotypes. A 39-year-old woman developed persistent, spreading upper limb pain following minor trauma. The pain was nondermatomal, disproportionate, and functionally disabling. Despite extensive evaluation, she did not meet the full Budapest criteria for CRPS type I or II. Alternative diagnoses were excluded, and a diagnosis of CRPS-NOS was made. The clinical pattern was consistent with a significant nociplastic pain component. She demonstrated significant pain relief following an ultrasound-guided stellate ganglion block. This case report highlights the diagnostic challenges of CRPS-NOS and underscores the importance of recognizing nociplastic pain mechanisms in atypical CRPS presentations. Incorporating a mechanism-based framework may improve diagnostic accuracy and guide more targeted, effective interventions.