534 - Uncontrollable Belching, an Atypical Symptom of Pectoralis Minor Syndrome

Case Diagnosis: A previously healthy 35-year-old female who presented with reproducible uncontrolled eructations secondary to pectoralis minor syndrome (PMS).

Case Description: Patient presented with a 12-month history of right upper extremity pain radiating from her neck with associated numbness and tingling. She denied any inciting events. Exam was significant for positive Spurling’s maneuver, right anterior and middle scalene muscle tenderness, and mild right-hand weakness. Belching was elicited by thoracic spine palpation and neck rotation. She had no myelopathic symptoms.

Electromyography/nerve conduction studies (EMG/NCS) and MRI’s of the right brachial plexus (BP) and cervical and thoracic spine were unremarkable. Ultrasound identified right subclavian/axillary vasculature prominence from the supraclavicular to infraclavicular regions deep to pectoralis minor. The right phrenic nerve was visualized and followed from the omohyoid muscle to the immediate supraclavicular region, where it was found close to the prominent vasculature. The belching was likely secondary to transient phrenic nerve compression by the vessels.

Symptoms resolved for four months following pectoralis minor nerve and muscle blocks, confirming diagnosis of PMS.

Discussions: Although 90% of PMS cases present with neurogenic symptoms, cyanosis, arm swelling, and anterior chest wall pain have been documented. This case illustrates that belching could be a symptom associated with PMS. To our knowledge, there have been no reports of PMS with eructations secondary to phrenic nerve irritation.

Because of the positional nature of PMS, static imaging via MRI or CT is rarely diagnostic of the condition. EMG/NCS is often unremarkable. Ultrasound can capture dynamic BP movement relative to positional changes. The “bowing” morphology seen on ultrasound of the pectoralis minor suggests PMS. This modality can identify compression sites along the BP that can serve as targets for nerve or muscle blocks.

Conclusions: Reproducible belching can be a unique symptom associated with PMS. Ultrasound can be used to help in the diagnosis of PMS.