Role of Dorsal Scapular Nerve Entrapment in Unilateral Interscapular Pain

Abstract Objective To determine the contribution of dorsal scapular nerve (DSN) entrapment to interscapular pain. Design A descriptive research study. Setting Institutional practice. Participants Consecutive patients with unilateral interscapular pain (n=55) were evaluated and were compared with healthy controls (n=30). Patients were assessed clinically and electrophysiologically. Electrophysiologic evaluation included motor conduction study of the DSN and electromyography of rhomboid major and levator scapula. Electrophysiologic workup for exclusion of other disorders was carried out. Interventions Not applicable. Main Outcome Measures Not applicable. Results Unilateral interscapular pain was reported by all patients. Etiologies of pain varied among the studied patients. Scapular winging was observed in 9 patients (16.4%). Electrophysiologic abnormalities consistent with DSN lesion were detected in 29 patients (52.7%). Twenty-five patients demonstrated electromyographic abnormalities recorded from rhomboid major and levator scapula. Prolonged latency of the compound muscle action potential was found in 4 patients on the affected side. Conclusions DSN entrapment is a frequent underlying causative factor for interscapular pain. Nerve entrapment at the scalenus medius or its stretch during overhead activities induces nerve trunk pain secondary to the sensitization of nociceptors within the nerve sheath. Myofascial pain syndrome of the rhomboids with entrapment of the nerve by taut bands is another source of pain. Last, the development of scapular winging may induce stretch of the cutaneous medial branches of the dorsal primary rami of thoracic spinal nerves. This would refer pain to the interscapular region. Awareness of possible DSN entrapment in cases of upper dorsalgia is highly indicated.