Courtney Aronica, DO
Resident Physician
Northwell Health
Commack, New York, United States
Roy F. Chen, MD
PGY-3
Northwell Health
Westbury, New York, United States
Areeb Chator, MD
Primary Care Sports Medicine Physician
Long Island Spine Rehabilitation Medicine
East Meadow, New York, United States
A 73-year-old male with no significant medical history presented with right index finger weakness. Three months prior, he had a skiing accident resulting in whiplash, right forearm trauma, and right clavicle fracture. Despite recovering from the initial injuries, physical exam showed persistent right index flexor digitorum profundus (FDP) weakness with otherwise intact neurological exam. Hand, wrist, and forearm MRI showed STIR hyperintensity in pronator quadratus (PQ), flexor digitorum superficialis (FDS), and FDP, with intact tendons. Brachial plexus MRI revealed delayed union of clavicular midshaft fracture with posterior displacement of the distal fragment, and segmental neuritis affecting the medial cord. C-spine MRI revealed multilevel severe degenerative changes without myelopathy. Electrodiagnostic testing demonstrated moderate right AIN neuropathy with active denervation, moderate bilateral median neuropathy at the wrist, and bilateral chronic C5-7 radiculopathy.
Discussions:
MRI and electrodiagnostic testing narrowed down the extensive differential diagnosis. While physical exam revealed only FDP weakness, electromyography showed active denervation in PQ and flexor pollicis longus (FPL), supporting the diagnosis of AIN neuropathy. Incomplete AIN syndrome presenting as isolated FPL or index FDP weakness is rare but documented.
MRI hyperintensity in the FDS, FDP, and PQ may indicate residual traumatic contusion that could cause compartmental AIN compression. Alternatively, it could be secondary to denervation atrophy from brachial plexitis or a physiologic variant of AIN partly innervating the FDS.
Brachial plexus injury is a potential complication of clavicular fracture, typically involving the medial cord secondary to direct pressure from hypertrophic nonunion. Our patient’s delayed fracture union, posteriorly displaced distal fragment, and medial cord neuritis support a diagnosis of brachial plexopathy.
Conclusions:
This patient's specific complaint of index FDP weakness led to an in-depth examination of the peripheral nerve pathway. This case highlights the integration of various physiatric diagnostic tools into a comprehensive and multifaceted approach.
