The dorsoscapular nerve in traumatic brachial plexus lesions.

The origin and course of the nerval innervation of the levator scapulae and rhomboid muscles was studied in four human cadavers. Special attention was given to surgical anatomy. The levator scapulae muscle receives two small segmental nerves from C3 and C4, respectively. The rhomboid muscle receives two segmental nerves, one from C4 and the other from C5. Moreover, in a series of 137 patients with a traumatic brachial plexus lesion, the linkage between levator scapulae and rhomboid muscle function impairment and site of the brachial plexus lesion was studied. Paresis of one or both of these muscles was noted in 13 cases. It was concluded that the rhomboid muscle may function on a single C4 nerve supply without any loss of strength. Arguments are put forward to support the relevance of rhomboid muscle testing in the assessment of brachial plexus lesions.