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Shoulder Double Crush Syndrome: A Retrospective Study of Patients with Concomitant Suprascapular Neuropathy and Cervical Radiculopathy
Daniel Miles, MD, University of Tennessee at Chattanooga, Chattanooga, TN, Yoshihiro Katsuura, MD, Hospital for Special Surgery, New York, NY and John Dorizas, MD, University of Tennesse at Chattanooga, Chattanooga, TN

Purpose: Double crush phenomena (compression along two points on a nerve) has been established between median neuropathy and cervical radiculopathy. Combined suprascapular neuropathy (SSN) and cervical C5/C6 radiculopathy termed "shoulder double crush syndrome" (DCS) has not been well examined. The purpose of this study was to identify patients who had clinical evidence of DCS of the suprascapular nerve and cervical spinal roots and to study clinic characteristics, electrodiagnostic findings, and treatment outcomes undergoing arthroscopic SSN nerve decompression compared to patients with isolated SSN.

Methods: 100 consecutive patients >18 years of age, who were positive for SSN on electromyography and motor nerve conduction studies undergoing suprascapular nerve decompression were included. Patients with evidence of shoulder DCS were identified based on cervical spine MRI and examination findings. Demographics, electrodiagnostic results, treatment courses, and clinical outcomes (visual analog scores and rotator cuff strength) following arthroscopic suprascapular nerve release were compared between patients with DCS versus isolated SSN.

Results: Thirty-one percent of patients had evidence of DCS versus 69% with isolated SSN. Median age was 53 years old, average duration of symptoms was 20 months prior to presentation and average follow-up time frame of 8.8 months after surgery. Two significant differences were noted on electrodiagnostic studies in DCS shoulders compared to isolated SSN. DCS patients had increased incidences of median neuropathy (51% vs. 30%) and less supraspinatus motor amplitude difference between the affected side and non-affected side compared to isolated SSN patients (2.62 vs. 3.44mV). There were significant decreases in VAS pain scores for all patients (isolated SSN and DCS) who underwent arthroscopic SSN decompression from initial presentation to final follow-up (6.52 vs. 3.01). There were statistically significant improvements in supraspinatus strength on MMT from pre-op to post-op (3.27 vs. 4.93) and infraspinatus strength (3.34 vs. 4.79).

Conclusion: DCS involving the cervical spine and SSN demonstrate clinical findings of cervical radiculopathy and shoulder girdle weakness and may show improvement in symptoms with SSN decompression. They may have decreased differences in suprascapular nerve amplitude between the affected and non-affected side making diagnosis of SSN difficult. This is likely related to bilateral denervation of the suprascapular nerve from bilateral foraminal lesions and is more likely to have median neuropathy. Physicians should be aware of and consider the possibility of DCS in patients with ill-defined shoulder pain and carefully evaluate for neck pathology with any shoulder evaluation as there is significant overlap between neck and shoulder symptomatology.
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