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Identify Erb's point (punctum nervosum), which is located on the posterior border of the sternocleidomastoid muscle midway between its attachments to the mastoid process, and the sternum and clavicle. At Erb's point, cutaneous branches of the cervical plexus (Figure 24.2) emerge from behind the posterior border of the sternocleidomastoid muscle. The four cutaneous nerves of the cervical plexus are the lesser occipital nerve, great auricular nerve, transverse cervical nerve, and supraclavicular nerve.
Along the superior aspect of the posterior edge of the sternocleidomastoid muscle, identify the lesser occipital nerve. It runs superiorly and innervates the skin superior and posterior to the ear.Links and References:
Grant's: 8.4
Netter:172