What is pectoralis minor syndrome and what are the first‑line and second‑line management options?

Pectoralis Minor Syndrome: Definition and Management

What is Pectoralis Minor Syndrome?

Pectoralis minor syndrome (PMS) is a form of neurogenic thoracic outlet syndrome caused by compression of the brachial plexus, axillary artery, and axillary vein beneath the pectoralis minor muscle in the retropectoralis minor space. 1, 2

• PMS presents with shoulder, neck, chest, and arm pain, along with paresthesia and weakness in the arm and hand 1
• The condition typically develops from repetitive overhead activity combined with scapular dyskinesia, leading to pectoralis minor shortening and decreased volume of the retropectoralis minor space 3, 4
• Women with breast hypertrophy and poor posture appear particularly susceptible due to postural overload 5
• Compression in the pectoralis minor space is actually rare compared to costoclavicular space compression, occurring in only a small percentage of neurogenic TOS cases 6

Diagnostic Approach

Clinical Evaluation

• Obtain detailed history including occupation, daily activities, sports participation, and trauma history 1
• Examine for scapulothoracic abnormal motion (STAM) and postural abnormalities, particularly scapular protraction and distalization 3, 4
• Look for diffuse shoulder girdle symptoms rather than focal findings 5

Imaging and Confirmatory Testing

• MRI without IV contrast is sufficient to diagnose neurogenic TOS and can demonstrate compression of neurovascular bundles in the pectoralis minor space 6, 7
• Chest radiography should be performed initially to exclude osseous abnormalities such as cervical ribs or first rib anomalies 7
• Arterial and venous Doppler ultrasound with dynamic investigation can display vascular compression 1
• Ultrasound-guided pectoralis minor muscle block is the definitive diagnostic test—positive response in appropriate clinical context confirms the diagnosis 2, 5

Critical Differential Diagnoses to Exclude

• Peripheral neuropathies, cervical radiculopathy, and space-occupying lesions must be ruled out 3
• Severe cervical spondylosis can contribute to or mimic TOS symptoms 6
• Other upper extremity pain syndromes can present similarly 1

First-Line Management: Conservative Treatment

Conservative treatment is successful in the majority of patients and should be the initial approach for all cases without acute vascular complications. 1, 2, 3

Structured Physical Therapy Protocol

• Pectoralis minor stretching exercises are the cornerstone of treatment 3, 4
• Periscapular muscle strengthening and retraining to correct scapular dyskinesia 3, 4
• Postural retraining to address chronically distalized and protracted scapular posture 3, 4
• Treatment duration should be 3-6 months before considering surgical intervention 7, 8

Adjunctive Measures

• Activity modification to avoid repetitive overhead motions 1
• NSAIDs for pain control if no contraindications exist 9
• Ultrasound-guided pectoralis minor injections can provide temporary relief and confirm diagnosis 5

Second-Line Management: Surgical Intervention

Surgical decompression should only be considered in compliant patients who fail conservative management after an adequate 3-6 month trial and respond favorably to diagnostic injections. 7, 8, 3

Surgical Options

• Arthroscopic pectoralis minor release (APMR) is the modern preferred approach, offering minimally invasive decompression with excellent outcomes 5, 4
• Open pectoralis minor release can be performed through various approaches 3
• Additional procedures may include suprascapular nerve release and brachial plexus neurolysis when indicated by preoperative workup 3, 4
• Endoscopic techniques can also address subclavius and interscalene compression if present 4

Surgical Outcomes

• Both open and arthroscopic release can be performed safely with effective resolution of neurogenic symptoms 3
• Most patients experience significant relief and restored baseline function after decompression 2
• Women with breast hypertrophy treated with APMR have demonstrated durable symptom resolution 5

Common Pitfalls to Avoid

• Do not proceed with surgery without documented failure of structured conservative management for 3-6 months 7, 8
• Do not rely solely on symptoms and positive diagnostic blocks without appropriate imaging to exclude other pathology 8
• Do not overlook concomitant cervical spine pathology that may be the primary cause of symptoms 6, 8
• Recognize that dynamic venous compression on imaging is commonly seen in asymptomatic individuals and requires clinical correlation 7, 8
• Ensure diagnostic ultrasound-guided injection confirms the diagnosis before proceeding to surgery 2, 5