Scapular winging secondary to serratus anterior dysfunction: analysis of clinical presentations and etiology in a consecutive series of 96 patients

Background This study aimed to establish the relative incidence of etiologies causing serratus anterior (SA) dysfunction in patients with proven abnormality on needle electromyography. Methods This was a retrospective review of patients with scapular winging secondary to SA dysfunction. Each patient underwent a detailed clinical, radiological, and neurophysiological assessment to arrive at the precise etiological diagnosis. Patients with atypical clinical features were referred for a neurologist’s assessment. Hematological and genetic testing were requested at the discretion of the neurologist. A scapular winging severity score based on clinical signs was devised to aid clinical grading. Results Between 2014 and 2020, a consecutive series of 108 patients with suspected SA dysfunction were assessed, of whom 96 met the inclusion criteria. There were 34 females and 62 males, with a mean age of 38 years (range, 15-77 years). Winging affected the right scapulae in 69 patients, the left scapulae in 17 patients, and was bilateral in 10 patients. This was caused by a myopathic disorder in 12 (12%) patients. Eighty-four (88%) patients had a long thoracic nerve lesion, caused by cervical pathology (2), iatrogenic injury (2), trauma (33), and neuralgic amyotrophy (NA) (47). Among those with NA, winging resolved spontaneously within 3 years of onset in 22 patients (mean duration, 16 months; range, 3-36 months). No patients recovered fully if their duration of winging lasted longer than 3 years. Patients with palsy secondary to NA tended to have a worse severity of winging than those due to a traumatic cause (P = .04). Conclusion NA accounted for approximately half of the patients with SA dysfunction; therefore, it is essential to also consider the differentials of myopathy, trauma, iatrogenic injury, and spinal pathology. We recommend the judicious employment of ancillary tests and a low threshold of referral to a neurologist, in order to arrive at the exact diagnosis to accurately guide patient treatment.