Biceps Activity Synchronous with Inspiration After Phrenic Nerve Transfer.

Abstract

A 26-year-old gentleman had a motor vehicle accident causing complete weakness of his right upper limb. On examination, his power was Medical Research Council (MRC) grade 0/5 in the right upper limb. Nerve conduction study revealed pan-brachial plexopathy. There was no spontaneous improvement in his power with conservative management, and he underwent nerve transfer surgery 8 months after his injury. Sural nerve was grafted between the phrenic nerve and biceps branch of the right musculocutaneous nerve. Needle electromyography (EMG) recording of right biceps brachii muscle was done 13 months after phrenic nerve transfer. Spontaneous activity in the form of fibrillations was seen during expiration (Fig A) as well as on inspiration (Fig B). Small and polyphasic motor unit action potentials (MUAPs) appeared when the patient inspired (see Fig B) but disappeared on expiration (see Fig A). The fibrillations suggested active denervation. The biceps power at this point of time was MRC grade 0/5 and no MUAP could be recruited by voluntary effort. However, the appearance of the MUAPs synchronous with inspiration suggested re-innervation and successful neurotization. The EMG recording is seen in the Video S1. Beginning 16 months after surgery, his power started improving in the right biceps and at 24 months postsurgery his power improved to MRC grade 3/5 in the right biceps. Phrenic nerve transfer to musculocutaneous nerve is a promising option in traumatic brachial plexus injury for restoration of elbow flexion in selected patients.1 There was improvement in biceps power to MRC grade ≥ 3 in about 74% of the patients after a mean duration of 38 months following the surgery in a study.2 Breathing has a considerable impact on elbow function after nerve transfer for elbow function reconstruction both clinically and electromyographically.3 The return of muscle power takes some time after surgery, but EMG can aid in early assessment by looking for MUAPs in biceps, which appear synchronous with inspiration. In another study, recovery of MUAPs occurred 6 months after nerve transfer surgery and became more apparent at 12 months. The percent of patients recovering “excellent” or “good” muscle strength in the biceps brachii was 80% after 18 months.4 The authors declare that there are no conflicts of interest. Video S1. Video shows needle electromyography recording of right biceps brachii after phrenic nerve transfer to musculocutaneous nerve for traumatic brachial plexopathy. Spontaneous activity (fibrillations) is seen at rest both in inspiration and on holding breath. Small, polyphasic motor unit action potentials (MUAPs) appear synchronous with inspiration and disappear on holding breath. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.