(Kiosk 3) Growing Bone and Losing Tone: Heterotopic Ossification Presenting as a Progressive Radial Neuropathy After Traumatic Brain Injury with Polytrauma: A Case Report

Case Diagnosis: 29-year-old male with right wrist and finger extension weakness.

Case Description or Program Description: Patient fell off a roof, sustaining a traumatic brain injury and multiple fractures, including the right humeral diaphysis. He underwent open reduction and internal fixation of the right humerus two and a half weeks post-fall. On admission to inpatient rehabilitation, his strength exam was notable for 4/5 with elbow extension, and 0/5 with wrist and finger extension in the right arm. Sensation was intact to light touch throughout his right arm at time of admission, however he noted decreased sensation over the dorsal aspect of his right hand and forearm by the time of his electromyography (EMG), which was performed a month and a half post-fall.

Setting: Neuromuscular clinic

Assessment/Results: EMG demonstrated a severe, axonal, right radial mononeuropathy localized between the nerve branches to the triceps and brachioradialis. Musculoskeletal ultrasound demonstrated heterotopic ossification (HO) at the mid-humeral diaphysis, partially encasing the radial nerve. Repeat EMG two months later demonstrated small interval improvement in the radial neuropathy, illustrated by a few nascent motor units in the brachioradialis muscle. Patient’s strength improved to 1/5 for wrist extension.

Discussion (relevance): Patient’s humerus fracture caused a posterior interosseous neuropathy, but the development of radial-dermatome sensory loss and proximal, radially-innervated motor impairments on EMG suggested a worsening radial sensorimotor neuropathy. This prompted more extensive imaging with musculoskeletal ultrasound, which demonstrated heterotopic ossification compressing the radial nerve, causing the proximal radial neuropathy.

Conclusions: Heterotopic ossification is a potential complication after orthopedic and traumatic brain injuries, and should be included on the differential of post-traumatic peripheral neuropathies. Progression of traumatic neuropathies should prompt advanced imaging such as ultrasound to investigate for structural lesions. Surgical resection of HO may hasten recovery of symptoms.