The anatomical study of the osteochondral, vascular and muscular relations of the superficial and deep cervical plexuses.
In standard anatomical textbooks, the formation of the cervical plexus is well defined; however the accurate differentiation into superficial and deep plexuses, their emerging patterns, and gross anatomical relations are not documented as expansively. In order to obtain detailed anatomical knowledge of the superficial and deep cervical plexuses, the investigation aimed to clarify the anatomy and variations of these plexuses, define possible anatomical landmarks, and record the relationship of the external jugular vein and muscles of the posterior triangle of neck to the branches of the superficial cervical plexus, and the relationship of the common carotid artery, internal jugular vein, sympathetic chain, cervical verterbrae, and vertebral artery to the deep cervical plexus. The studies utilized the gross anatomical dissection, morphological and statistical analyses of forty fetal and fifteen adult cadaveric, formalinized specimens. The branches of the superficial cervical plexus emerged from the posterior border of the sternocleidomastoid muscle at the great auricular point (situated in the middle third of the muscle) and was described as ascending (lesser occipital, great auricular, transverse cervical nerves) and descending (supraclavicular nerves). Further, these branches were recorded according to their branching patterns, relations to the external jugular vein and variations. The branching patterns are described as single, duplicate and triplicate. The external jugular vein was constantly located inferior to the great auricular nerve, superior to the transverse cervical nerve and intertwined with the branches of the supraclavicular nerves. Variations of the branches of the superficial cervical plexus were observed only in fetuses and classified according to their course, branching patterns and communications. The emerging point of the branches of the superficial cervical plexus on the sternocleidomastoid muscle, were determined according to the seven types of “emerging pattern” classification by Kim et al., (2002). In order to record the deep cervical plexus, the sternocleidomastoid muscle was reflected with the following observation: the ventral rami of the second and third cervical nerves emerged between the scalenus anterior and scalenus medius muscles, and the third and fourth cervical nerves was located at the lateral edge of scalenus medius muscle. The deep cervical plexus was described as communicating, muscular, ansa cervicalis, and phrenic nerves. The superior cervical ganglion constantly communicated with the ventral rami of the cervical nerves; and the hypoglossal communicated with the superior root of the ansa cervicalis. The muscular branches were observed to the scalenus anterior and scalenus medius muscles with an anomalous branch to the sternocleidomastoid muscle. The ansa cervicalis demonstrated a degree of variation with regard to its origin, course and formation of the loops. The phrenic nerve arose from the ventral rami of the third, fourth and fifth cervical nerves and descended on the lateral border of the scalenus anterior muscle. The precise understanding of the anatomy of the superficial and deep cervical plexuses together with variations may assist anesthetists and surgeons to accurately identify the vascular, neural and muscular structures and reduce the risks of complications when performing neural blocks in regional anesthesia, facial rejuvenation surgery and parotidectomies.