920 - Unmasking Idiopathic Neuralgic Amyotrophy: A Compelling Case Report

Friday, February 23, 2024

5:00 PM – 6:30 PM EDT

Presenting Author(s)

AR

Alexa M. Ryder, MD MBA

Resident Physician
McGovern Medical School at UTHealth
Houston, Texas, United States

Co-Author(s)

VB

Vishal Bansal, MD

Resident Physician
UTHealth
Houston, Texas, United States

Corresponding Author(s)

KP

Kemly Philip, MD, PhD, MBE (she/her/hers)

Assistant Professor
The University of Texas Health Science Center at Houston
Houston, Texas, United States

Co-Author(s)

AS

Ajai Sambasivan, MD

Associate Professor
The University of Texas Health Science Center at Houston
Houston, Texas, United States

Case Diagnosis: Idiopathic Neuralgic Amyotrophy

Case Description: 51 year-old male with past medical history of HIV and recent mononucleosis infection presented to clinic with right shoulder pain. 9 months prior, he was lifting his arms to make his bed when he experienced a popping sensation, followed by painful pulling/pressure sensation in the right shoulder. On examination, his pain was described as a severe burning sensation and associated with diffuse numbness, tingling and swelling. Physical examination was notable for right atrophic supraspinatus and infraspinatus muscle and shoulder in a depressed position. Sensation to pinprick was diminished in right C4-C5 distributions, ⅘ strength with shoulder abduction, elbow flexion and extension, and thumb abduction and reflexes intact and multiple positive provocative maneuvers on the right (empty can, crossed adductor, O’brien’s, Neer, and Hawkins).

Discussions: EMG showed chronic, poorly localized right brachial plexopathy, and less likely cervical radiculopathy given abnormal LABC response. MR cervical spine was pertinent for central disc protrusion at C6-C7. MR Brachial plexus/shoulder showed mild supraspinatus and infraspinatus muscle edema, possibly due to denervation changes. MR right shoulder showed transient edema and atrophy in these muscles. The patient received gabapentin for neuropathic pain and PT for spine/scapular strengthening with no appreciable relief. Plans for a scapular nerve block await insurance approval.

He was diagnosed with Idiopathic Neuralgic Amyotrophy based on MRI and EMG findings. Literature shows common association with viral illness, trauma, surgery, immunization or vascular etiology. It is possible that our patient’s HIV and mononucleosis played a role as an auto-immune reaction in addition to the initial traumatic movement event.

Conclusions: This case illustrates an uncommon clinical presentation of Idiopathic Neuralgic Amyotrophy. Clinicians should be cognizant of this differential and consider the possibility of multiple risk factors that can predispose the patient to developing this entity and limit patient morbidity and costly diagnostic work-up.