Evaluating The Accuracy of Electrodiagnostic Study in Detecting Suprascapular Neuropathy in Cases of Chronic Shoulder Pain

Background: Electrophysiological study involving electromyography (EMG) and nerve conduction studies are important tools for diagnosis of entrapment neuropathy, as it had a great role in determining the etiology, and severity of entrapment, confirming the diagnosis, detecting the site, quantifying the degree of compression as well as documenting the progression and prognosis of the disorder. Objectives: To assess the accuracy of electrophysiological studies in diagnosing suprascapular neuropathy in cases of chronic shoulder pain. Patients and Methods: A controlled randomized prospective study was carried out on 180 patients with chronic shoulder pain. They were recruited from outpatient clinics of rheumatology, physical medicine, and rehabilitation at our university. Electrophysiological study regarding nerve conduction study (NCS) of both suprascapular nerves and EMG studyto the supraspinatus and infraspinatus muscles were carried out. Results: Approximately 11.1% of patients of the current study were diagnosed as suprascapular neuropathy regarding abnormal motor nerve conduction study results, and 9.4% of patients were diagnosed based on abnormal electromyographic findings. The latency and amplitude of suprascapular nerve on motor nerve conductive (MNC) at cutoff value of >2.35, and <6.95 had accuracy of 69.1%, and 66.7% to detect the occurrence of suprascapular neuropathy. The duration, and amplitude of supraspinatus MUAP on EMG at cutoff value of >5.85, and <1.175 had an accuracy of 74.7%, and 74%, also, the duration, of infraspinatus MUAP on EMG at cutoff value of >6.1 had 79% accuracy, that means at those points, we could differentiate between the affected and non-affected suprascapular nerve. Conclusion: Electrophysiological study involving electromyography (EMG), and nerve conduction studies is an important and accurate tool for diagnosing suprascapular neuropathy in cases of chronic shoulder pain, with accurate and precise cutoff points, in addition to clinical examination and radiological findings.