1651 - Silent EMG: Proximal Median Injury Post-GSW

32 year old right-handed male inmate with chronic median-territory sensory symptoms (thumb, index, middle fingers) and forearm burning pain following a ballistic hand injury 2 years prior. Clinical exam showed thenar atrophy, focal forearm and deep-compartment weakness (pronator teres/pronator quadratus pattern), positive Tinel at the carpal tunnel and an abnormal OK sign. Electrodiagnostic testing of the symptomatic limb was interpreted as normal. No median mononeuropathy at the wrist or radiculopathy.


Case Description:

The patient sustained a GSW to the left hand with a healed base of the second metacarpal fracture and a retained radiopaque fragment. Symptoms persisted despite conservative care. Neurologic exam demonstrated weakness of forearm pronation and wrist flexion/extension (3/5–4/5), thenar wasting, thumb IP flexion contracture with Boutonnière-type posture, and reduced median-distribution sensation. EMG/NCS showed normal distal motor and sensory conduction studies, while needle exam revealed isolated increased insertional activity in pronator teres. Orthopedics provided a wrist brace and local steroid injection.


Discussions:

Ballistic nerve trauma commonly produces focal scarring, neuroma-in-continuity, or proximal axonal injury that distal NCS/EMG can miss, particularly when testing is limited by pain or when lesions are primarily sensory. The combination of forearm-predominant weakness, thenar atrophy, isolated pronator irritability, and a retained foreign body increases the pretest probability for a proximal median nerve lesion or entrapment within the forearm. This case matters because it exposes a diagnostic blind spot: reliance on normal distal electrodiagnostics alone may delay targeted imaging, localization, and referral, risking persistent dysfunction and missed surgical windows. High-resolution nerve imaging can alter management.


Conclusions:

A normal distal electrodiagnostic study does not exclude clinically significant proximal median nerve injury after ballistic trauma. We recommend high-resolution forearm ultrasound or MR neurography to evaluate for focal scarring/entrapment, continued multimodal conservative care, and expedited hand/nerve surgical consultation if imaging demonstrates compressive lesion or neuroma-in-continuity.