Microanatomy of the brachial plexus roots and its clinical significance.

PURPOSE: To provide the anatomical basis of brachial plexus roots for the diagnosis and treatment of brachial plexus root avulsion injury.
METHODS: The morphological features of brachial plexus roots were observed and measured on 15 cervicothoracic spine of adult cadavers. The relationship of brachial plexus nerve roots and the surrounding tissues also were observed, as well as the blood supply of anterior and posterior roots of the brachial plexus.
RESULTS: Origination of the nerve roots in the dorsal-ventral direction from the midline was fine-tuned at each level along the spinal cord. The minimum distance of the origin of the nerve root to midline was 2.2 mm at C 5, while the maximum was 3.1 mm at T 1. Inversely, the distance between the origin of the posterior root and the midline of the spinal cord gradually decreased, the maximum being 4.2 mm at C 5 and minimum 2.7 mm at T 1. Meanwhile, there was complicated fibrous connection among posterior roots of the brachial plexus. The C 5-6 nerve roots interlaced with tendons of the scalenus anterior and scalenus medius and fused with the transverse-radicular ligaments in the intervertebral foramina. However, these ligaments were not seen in C 7-8, and T 1. The blood supply of the anterior and posterior roots of the brachial plexus was from the segmental branches of the vertebral artery, deep cervical artery and ascending cervical artery, with a mean outer diameter of 0.61 mm.
CONCLUSIONS: The systematic and comprehensive anatomic data of the brachial plexus roots provides the anatomical basis to diagnose and treat the brachial plexus root avulsion injury.