Electrophysiologic study of C7 nerve root innervated muscles

Objective To analyze the representative muscles innervated by C7 nerve root via electrophysiologic testing. Methods Sixteen patients of root avulsions of the brachial plexus who underwent eontralateral C7 tranafer were involved in the study. Intra-operatively compound muscle action potentials CMAPs in various upper limb muscles were recorded while C7 nerve root was stimulated. Amplitudes of CMAPs were measured and compared to determine the representative muscles of the C7 nerve roor Results Electrophysiologic data showed that lattiaaimus dorsi muscle and triceps brachii muscle best represent function of the C7 nerve root. In all 16 cases stimulation of C7 resulted in higher CMAP amplitude in long head of the triceps than when any other nerve root was stimulated. CMAP amplitude of lattissimus dorsi muscle elicited by C6 stimulation was similar to that elicited by C7 stimulation in 4 cases (25.0%). Conclusion Long head of the triceps and lattissimus dorsi muscle are representative muscles of C7 nerve root. Key words: Brachial plexus;  Electrophysiology;  C7 nerve root