Suprascapular neuropathy in a shoulder referral practice

Abstract

Hypothesis: Suprascapular neuropathy (SSN) is considered a rare condition, and few studies have analyzed how commonly it is encountered in practice. Electrophysiologic studies are the gold standard for diagnosis; however, there is no consensus on diagnostic criteria. We hypothesized that SSN would be frequently diagnosed by electrophysiologic testing in a subset of patients with specific clinical and radiographic findings suggestive of the pathology. This study characterizes SSN in an academic shoulder referral practice and documents the electrodiagnostic findings that are currently being used to diagnose the condition.

Materials and methods: A retrospective review of a 1-year period was used to identify all patients who completed electrodiagnostic studies to evaluate the suprascapular nerve. Clinical exam findings and associated shoulder pathology was documented. The specific electromyography (EMG) and nerve conduction studies (NCS) findings were analyzed.

Results: Electrodiagnostic results were available for 92 patients, and 40 (42%) had confirmed SSN. Patients with a massive rotator cuff tear were more likely to have an abnormal study than those without a tear (P = .006). The most common electrodiagnostic abnormalities were abnormal motor unit action potentials (88%), whereas only 33% had evidence of denervation. The average latency in studies reported as diagnostic of SSN was 2.90 ± 0.08 milliseconds for the supraspinatus and 3.78 ± 0.14 milliseconds for the infraspinatus.

Discussion: An electrodiagnostically confirmed diagnosis of SSN was seen in 4.3% of all new patients and in 43% of patients with clinical or radiographic suspicion of SSN. Clinical evaluation may be difficult because other shoulder pathology can have overlapping symptoms.

Conclusion: Shoulder surgeons should consider electrophysiologic evaluation of patients with clinical or radiographic signs of SSN and be cognizant of the parameters that constitute an abnormal study.