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Musculoskeletal and Sports Medicine

(Kiosk 2) Right-sided Anterior Interosseous Nerve (AIN) Lesion Following Limestone Shoveling: A Case Report

Thursday, November 16, 2023
5:00 PM – 7:00 PM CT

    Primary Author(s)

  • Dianna H. Nguyen, Other

    DO-PhD Student
    University of North Texas HSC Fort Worth Texas College of Osteopathic Medicine, Texas

    • Co-Author(s)

  • DH

    Dawson Hinkley, Other

    Osteopathic Medical Student
    University of North Texas HSC Fort Worth Texas College of Osteopathic Medicine
    Springtown, Texas

  • Angela Nwankwo, MD

    Resident Physician
    Baylor College of Medicine PM&R
    Fort Worth, Texas

  • NN

    Nnaemeka Nweke, MD

    PGY3 Resident
    Baylor College of Medicine PM&R Program
    Houston, Texas

  • OS

    Omar F. Selod, DO

    Doctor of Osteopathic Medicine
    n/a
    Fort Worth, Texas

Case Diagnosis: Right-sided anterior interosseous nerve (AIN) lesion.

Case Description or Program Description: A 76-year-old female presented with right thumb and index finger weakness which occurred after shoveling limestone 3 months earlier. She first noticed difficulty flexing her right thumb and index finger, along with right forearm and elbow pain. She denied wrist/neck pain or numbness/tingling. Her weakness has persisted since the incident. On examination, patient demonstrated 2/5 muscle strength for right flexor pollicis longus (FPL), 1/5 for right flexor digitorum profundus (FDP) to second digit, and otherwise 5/5 for bilateral upper extremities. Sensation was intact throughout, and reflexes were 2/4 bilaterally for upper extremities. Patient was unable to make an “okay” sign with right thumb and index finger.

Setting: Outpatient PM&R clinic

Assessment/Results: Patient underwent nerve conduction (NCS)/electromyography (EMG) studies to evaluate for AIN lesion versus cervical radiculopathy. NCS was normal, while EMG findings revealed moderate right-sided AIN lesion with decreased recruitment during needle evaluation of the right pronator quadratus and right FDP to second digit. Patient was advised to follow-up with her hand surgeon for further management and PM&R clinic in 2 months.

Discussion (relevance): AIN injuries make up only 1% of all upper extremity palsies. AIN lesion involves injury to the motor branch of the median nerve that supplies the forearm muscles, including the FPL, pronator quadratus, and the FDP to the index and middle fingers. AIN lesions can result in weakness/paralysis of these muscles, leading to difficulty in grasping, grip strength, and wrist/finger flexion. The AIN can be compressed under the deep head of the pronator teres, fibrous bands, or anomalous muscles.

Conclusions: AIN lesions occur due to trauma or compression, and there are multiple places where entrapment can occur. AIN injury can impair a patient’s functional ability and quality of life. It is important to recognize therapeutic and rehabilitation efforts available to treat this rare condition.