Why does a deep trapezius strain produce referred pain to the anterior chest/airway and to the posterior arm near the triceps?

Understanding Referred Pain from Deep Trapezius Muscle Injury

Deep trapezius muscle injury produces referred pain to the anterior chest, airway, and posterior arm due to shared cervical nerve innervation (C3-C4), convergence of sensory pathways in the cervical spinal cord, and the anatomical relationship between cervical structures and the brachial plexus.

Neuroanatomical Basis for Referred Pain Patterns

Cervical Nerve Innervation

• The trapezius muscle receives motor and sensory innervation not only from the spinal accessory nerve (CN XI) but also from cervical nerve roots C2-C4, with C3-C4 being the predominant pattern (found in 83% of specimens) 1
• These cervical nerves contain both motor axons and sensory fibers that transmit pain signals from the trapezius muscle 1
• The C3-C4 nerve roots also provide sensory innervation to the anterior chest wall, explaining the radiation of trapezius pain to the front center chest 2

Convergence of Sensory Pathways

• Cervical afferent pathways from the trapezius and neck structures converge in the cervical spinal cord with pathways that normally transmit sensation from the chest and upper extremities 2
• This convergence creates "cross-talk" where the brain misinterprets the origin of pain signals, producing referred pain to areas distant from the actual injury site 2
• The cervical spine's sensory pathways are involved in coordination of cervical and vestibular reflexes, and dysfunction leads to aberrant signaling that manifests as referred symptoms 2

Specific Referral Patterns Explained

Anterior Chest and Airway Discomfort

• Cervical strain (which includes deep trapezius injury) produces persistent headache and can cause pain that radiates to areas innervated by the same cervical nerve roots, including the anterior chest 2
• The C3-C4 nerve roots that innervate the trapezius also contribute to sensory innervation of the phrenic nerve distribution and anterior chest wall structures 2
• This shared innervation explains why deep trapezius pain can be perceived as chest or airway discomfort, mimicking more serious cardiopulmonary conditions 2

Posterior Arm Near Triceps

• The brachial plexus (which innervates the triceps and posterior arm) originates from C5-T1 nerve roots but has anatomical proximity and neural connections with the C3-C4 roots that innervate the trapezius 2
• Cervical spine dysfunction and muscle injury create somatosensory dysfunction with aberrant signaling along cervical afferent pathways 2
• Patients with cervical strain commonly experience radicular symptoms (pain, paresthesia, weakness) in the upper extremities, including the posterior arm region 2
• The trapezius muscle's role in scapular stabilization means that dysfunction affects the entire shoulder girdle, potentially causing compensatory strain and referred pain down the arm 3, 4

Clinical Implications and Pitfalls

Distinguishing from Serious Pathology

• Critical caveat: Anterior chest pain from trapezius injury can mimic life-threatening conditions including acute coronary syndrome, aortic dissection, or pulmonary embolism 2
• The presence of musculoskeletal features helps differentiate: pain reproducible with palpation of the trapezius, restricted cervical range of motion, and absence of cardiac risk factors or hemodynamic instability 5, 2
• Red flags requiring urgent evaluation include: pulse deficits, blood pressure differentials between arms, signs of heart failure, or neurological deficits suggesting myelopathy 2, 5

Assessment Approach

• Palpate for trigger points in the trapezius with focal tenderness, particularly in the middle and lower trapezius segments where C3-C4 innervation is prominent 5, 6
• Assess for cervical spine involvement: pain with cervical motion, paraspinal tenderness, suboccipital muscle tenderness, and upper extremity myotome weakness 2
• Document the pain quality: trapezius-referred pain is typically described as deep, aching, and positional, rather than the sharp, tearing quality of vascular emergencies 2

Management Considerations

• Conservative treatment with NSAIDs, activity modification, and therapeutic exercises is appropriate for uncomplicated trapezius pain without red flags 5
• Imaging is not indicated initially unless conservative treatment fails after 6 weeks or red flags are present 5
• The lower trapezius in particular shows decreased strength and altered activation patterns in patients with shoulder and neck pain, requiring specific attention during rehabilitation 7