1549 - Brachial Plexopathy Secondary to Subscapularis Recess Effusion: A Case Report

Thursday, February 19, 2026

5:00 PM - 6:30 PM AST

Presenting Author(s)

MF

Morris Franco, DO

Dr. Morris Franco- Transitional year resident
Ocean University medical center
Long Branch, New Jersey, United States

Co-Author(s)

AS

Arpun Shah, DO, MPH

Resident Physician
Inspira Health Network
Mullica Hill, New Jersey, United States
RB

Raisa Bakshiyev, MD

Assistant Professor
Hackensack Meridian Health
millstone, New Jersey, United States

Submitter(s)

MF

Morris Franco, DO

Ocean University medical center
Long Branch, New Jersey, United States

Case Diagnosis: Brachial plexopathy secondary to compression from subscapularis recess effusion

Case Description: The patient, a 62-year-old male veteran, reported chronic right shoulder pain with recent weakness and tingling radiating down the arm. A physical exam displayed right deltoid atrophy, fasciculations, and sensory changes in a radial nerve distribution, up until the wrist. MRI showed a glenohumeral joint effusion extending into the subscapularis recess with a labral cyst. Ultrasound confirmed effusion compressing the brachial plexus, consistent with posterior cord involvement. Electrodiagnostic studies supported a focal neuropathy with absent right ulnar sensory nerve action potential but otherwise preserved conduction. The diagnosis of brachial plexopathy from chronic shoulder joint effusion was established, representing a rare mechanical etiology distinct from more common causes such as trauma, neoplasm, or iatrogenic injury. Ultrasound-guided aspiration yielded thick, chronic-appearing fluid, followed by corticosteroid injection. At three-week follow-up, he reported 80% improvement in symptoms, with ultrasound confirming effusion resolution.

Discussions: Brachial plexopathy commonly arises from trauma, neoplasm, or iatrogenic injury. In this case, a right shoulder effusion caused subscapularis recess distension and posterior cord compression, leading to focal weakness and sensory loss. This demonstrates the importance of considering effusion-related mass effects in plexopathies, particularly in patients with chronic shoulder pathology. Ultrasound was used as both a diagnostic tool for localizing the lesion and as a guide for aspiration. Symptom improvement after aspiration and corticosteroid injection supports both mechanical and inflammatory contributions.

Conclusions: Subscapularis recess effusion is a rare but clinically significant cause of brachial plexopathy. This case demonstrates that effusion-related compression can mimic typical etiologies, yet respond favorably to minimally invasive management. Ultrasound provides an accessible, reliable modality for diagnosis and intervention, providing direct visualization of effusion and brachial plexus involvement. Clinicians should consider effusion-related mass effect in the differential diagnosis of unexplained upper extremity weakness or paresthesias in patients with chronic shoulder pain.