Ultrasound-Guided Dextrose Hydrodissection for Mixed Sensory–Motor Wartenberg’s Syndrome Following a Healed Scaphoid Fracture: A Case Report

<b>Background and Clinical Significance</b>: Wartenberg's syndrome (cheiralgia paresthetica) is classically described as a pure sensory neuropathy of the superficial branch of the radial nerve (SBRN). However, in rare circumstances, dynamic mechanical irritation around the radial styloid may produce an atypical clinical phenotype with concurrent motor impairment, broadening the clinical significance of recognizing motion-related compression mechanisms. <b>Case Presentation</b>: A 35-year-old woman presented with persistent dorsoradial wrist pain and numbness, accompanied by progressive weakness of thumb extension, five years after a conservatively treated nondisplaced scaphoid fracture. Neurological examination demonstrated sensory loss in the SBRN distribution and Medical Research Council (MRC) grade 3/5 strength of the extensor pollicis longus (EPL). Nerve conduction studies revealed a markedly prolonged EPL motor latency (4.5 ms; normal ≤ 2.5 ms) with preserved sensory conduction. High-resolution ultrasound showed focal enlargement of the SBRN (cross-sectional area 0.13 cm²) and, critically, dynamic snapping of the nerve over the radial styloid that reproduced the patient's symptoms. The patient underwent ten weekly sessions of ultrasound-guided hydrodissection with 5% dextrose. After treatment, the pain Visual Analog Scale improved from 8/10 to 0/10 and EPL strength recovered to MRC 5/5. Follow-up nerve conduction studies demonstrated normalization of EPL motor latency (2.1 ms), and repeat ultrasound confirmed resolution of SBRN enlargement and snapping. <b>Conclusions</b>: This case expands the phenotype of Wartenberg's syndrome to include mixed sensory-motor involvement associated with dynamic SBRN snapping at the radial styloid. Dynamic ultrasound was pivotal for identifying the motion-dependent mechanism, and ultrasound-guided 5% dextrose hydrodissection achieved complete sensory and motor recovery as a minimally invasive and effective treatment option.