Adam Mouldi, MD
Medical Student
Lewis Katz School of Medicine at Temple University
Philadelphia, Pennsylvania, United States
Maitland B. Wiren, DO
Resident Physician
Temple University Hospital
Philadelphia, Pennsylvania, United States
Abhishek Shrinet, MD
Resident Physician
Temple University Hospital
Philadelphia, Pennsylvania, United States
A 23-year-old male with right hand weakness and numbness presents to electromyography (EMG) clinic after a comminuted ulnar fracture from a gunshot wound to his right forearm. He reported being unable to straighten his 4th and 5th digits and noted his hand looks “skinnier.” Physical examination revealed atrophy of the first interosseous muscle and decreased tone in the intrinsic hand muscles. Strength was 0/5 in abduction of the 2nd through 5th digits, Froment’s sign was positive, and sensation was absent in the ulnar nerve distribution. EMG/NCS showed evidence of ulnar nerve mononeuropathy with axonal injury and active denervation to the 1st dorsal interosseous and FCU proximal to the injury. Findings suggested axonotmesis but couldn’t rule out neurotmesis. Musculoskeletal ultrasound showed no evidence of nerve transection or traumatic neuroma at the mid aspect of the forearm and identified multiple bony fragments.
Discussions:
Gunshot wounds with ulnar shaft fracture typically result in ulnar nerve axonotmesis, where axonal damage occurs without disrupting the nerve’s connective structure. In rare cases, ulnar nerve neurotmesis, a complete nerve transection, requires urgent surgical intervention. Physical exam and EMG/NCS usually suffice to distinguish axonotmesis from neurotmesis. In this patient, EMG/NCS couldn’t differentiate between them, making musculoskeletal ultrasound essential for assessing nerve continuity and identifying bony fragments abutting the ulnar nerve. This combined EMG/NCS and ultrasound approach is crucial for guiding treatment decisions, balancing conservative therapy and possible surgical intervention.
Conclusions:
Understanding the ulnar nerve’s course in the elbow and forearm is crucial for accurate diagnosis and intervention. EMG/NCS assesses nerve conduction and functional deficits, while musculoskeletal ultrasound evaluates structural integrity and potential compression sites. Comprehensive assessment with these modalities is essential for staging nerve injuries, determining surgical intervention needs and rehabilitation.
