1001 - Post-Radial Fracture Hematoma-induced AIN Syndrome in the Presence of CTS

Friday, February 20, 2026

5:00 PM - 6:30 PM AST

Presenting Author(s)

CM

Caroline Madigan, BS

Medical Student (MS4)
Chicago Medical School at Rosalind Franklin University
Chicago, Illinois, United States

Co-Author(s)

NU

Nathaniel Ung, BS

Medical Student (MS4)
Chicago Medical School at Rosalind Franklin University
Chicago, Illinois, United States
ML

Martin Lanoff, MD

Physician
Chicago Medical School at Rosalind Franklin University
Libertyville, Illinois, United States

Submitter(s)

CM

Caroline Madigan, BS

Chicago Medical School at Rosalind Franklin University
Libertyville, Illinois, United States

Case Diagnosis: AIN Syndrome and CTS

Case Description: 73 y/o female with a history of b/l carpal tunnel syndrome release presenting with weakness in the L index finger and thumb L index finger following a mechanical fall from standing height (+HS, -LOC). She sustained a L nondisplaced distal radius fracture and a large L UE hematoma. She was casted for 8 weeks with and first noticed weakness with L-sided hand grasp after cast removal that did not resolve with OT. She also reported numbness and tingling in the L hand. Evaluated at 12 weeks.

PE:
ROM: Cervical/wrist WNL
Motor: 3/5 L distal thumb flexion (FPL), L distal 2nd digit DIP flexion (FDP). Unable to form a complete circle with thumb and index finger on L for “OK sign”
Reflexes: Triceps/Biceps/Brachioradialis 2+ b/l, Hoffman negative
Sensory: Decreased light touch distal L index finger
Provocative maneuvers: Spurling’s & Lhermitte's neg, Tinel’s neg at carpal tunnel
No thenar atrophy

Discussions:
Initial EMG/NCS showed moderate L and mild R CTS. Subsequent EMG testing revealed spontaneous activity in the PQ, FPL & FDP c/w AIN syndrome on the L, with concurrent CTS.

This is a patient with a history of CTS presenting with new onset isolated motor deficits following a nondisplaced distal radius fracture with casting and a LUE hematoma. While her symptoms were initially attributed to worsening CTS, further evaluation revealed AIN syndrome, characterized by weakness in the FPL and FDP to the index finger. AIN is a rare motor neuropathy of the median nerve, typically managed with activity modification, NSAIDs, and rarely surgical decompression.

Conclusions: This case highlights the importance of distinguishing AIN syndrome from CTS, particularly in patients with overlapping symptoms, risk factors, or recent trauma.