Initial Electromyography Fails to Predict Long-Term Outcome of Isolated Serratus Palsy

The course of isolated serratus palsy is difficult to predict, especially if, in initial electromyographic examination, long thoracic nerve function is totally absent. How initial electromyography correlates with long-term outcome of isolated serratus palsy is unknown. We evaluated initial electromyographic examinations of isolated serratus palsy patients and compared these to their long-term outcome. We hypothesized that long-term outcome after electromyographic examination-verified partial nerve injuries is better than that seen in cases of total nerve injuries.

We retrospectively reviewed 90 patients with isolated serratus palsy and with initial electromyographic examination treated by brace or observation only, by determining pain, range of motion, and degree of scapular winging after a mean follow-up of 17.8 years.

Initial electromyographic examination showed total denervation in 21 cases (22%), partial severe denervation in 30 (33%), and partial moderate or slight denervation in 39 (44%). Recovery of serratus muscle function occurred in 17/21 cases (81%) of total denervation and in 47/69 cases (68%) of partial denervation, p = 0.247. Mean flexion in total denervation recovered to 152° and in partial to 157°, p = 0.301, and abduction to 173° and 174°, p = 0.970. In total denervation, 60% of patients were pain-free, in partial, 48%, p = 0.338. The duration of scapular winging among those 42 who subjectively recovered averaged 15.1 months, in 13 patients with total denervation 15.9 months, and in 29 patients with partial denervation 14.7 months (p = 0.599).

Initial electromyographic examination does not predict clinical outcomes: ROM, pain, scapular winging and strength, but partial denervation may negatively predict subjective outcome.