Disclosures: Austin M. Grant, MD: No financial relationships or conflicts of interest

Case Description: The patient presented with numbness and pain of her right upper limb radiating to her right thumb for over a year. Her symptoms were present at rest and worsened with shoulder abduction and flexion and while running. Prior magnetic resonance imaging (MRI) of her shoulder and cervical spine were unremarkable. She underwent a 1st rib resection after MRI suggested costoclavicular compression of the subclavian vein, with only partial relief of her symptoms. She was referred to the clinic for a dynamic ultrasound evaluation.

Setting: Outpatient Clinic

Patient: A 20-year-old female basketball player Assessment/

Results: There were no static brachial plexus abnormalities seen on ultrasound however there is marked bowing of the pectoralis minor and reproduction of symptoms with shoulder abduction. Inspection of the brachial plexus showed an anterior position of the lateral cord relative to the axillary artery that was being dynamically compressed by the very tight pectoralis minor with shoulder abduction and flexion.

Discussion: Dynamic compression of the neurovascular structures by a tight or dystonic pectoralis minor is one of a number of potential causes of thoracic outlet syndrome. The high resolution as well as the dynamic capabilities of ultrasound make it an ideal modality for assessment in the retropectoral region. In this case, the identification of the slightly anomalous anterior position of the lateral cord was shown to be a predisposition for the neuritic symptoms and also served as an explanation for the numbness predominantly in the thumb and radial aspect of the hand rather than the more typical medial side.

Conclusion: High frequency ultrasound can be used in the assessment of dynamic compression in retropectoral thoracic outlet entrapment and also be used to identify anomalous variations that serve as a predisposition.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/ultrasound-assessment-of-retropectoral-thoracic-outlet-compression-a-case-report/