Lesser occipital nerve

The lesser occipital nerve (Latin: nervus occipitalis minor), also called the occipitalis minor, is a sensory cutaneous branch of the cervical plexus that supplies the skin in the lateral part of the scalp and the skin of the posterior aspect of the auricle. It usually arises from the anterior (ventral) ramus of the second cervical spinal nerve (C2). However, it might also receive fibers from the third cervical spinal nerve (C3).

At first, the lesser occipital nerve passes anterior to the spinal accessory nerve (CN XI). It then curves around the spinal accessory nerve and reaches the sternocleidomastoid muscle (SCM). The lesser occipital nerve also curves around the posterior border of the SCM, emerging at the punctum nervosum (Erb's point), which is found in the middle of the posterior border of the SCM. From the punctum nervosum, the lesser occipital nerve ascends parallel to the posterior border of the SCM towards the skull base. Sometimes it also pierces through the sternocleidomastoid.

Near the occipital bone, the lesser occipital nerve, together with other sensory branches of the cervical plexus (great auricular, transverse cervical and supraclavicular nerves), penetrates the deep cervical fascia. At this moment, it gives off several branches. Finally, the lesser occipital nerve and its branches ascend further over the occipital region and reach the scalp to supply the skin covering it. The terminal branches of the lesser occipital nerve form anastomoses with branches of the great auricular nerve, greater occipital nerve and sometimes also with the posterior auricular nerve - a branch of the facial nerve (CN VII).

Overall, the lesser occipital nerve has several communicating branches and three cutaneous branches - auricular, mastoid and occipital. They supply the regions after which they are named. In the scalp, the lesser occipital nerve gives off an auricular branch that supplies the posterior part of the auricle. It innervates the upper and medial third of the auricle and communicates with the posterior (mastoid) branch of the great auricular nerve.

References:

1. Gray, H., & Carter, H. (2021). Gray’s Anatomy (Leatherbound Classics) (Leatherbound Classic Collection) by F.R.S. Henry Gray (2011) Leather Bound (2010th Edition). Barnes & Noble.
2. Tubbs, S. R., Rizk, E., Shoja, M., Loukas, M., Barbaro, N., & Spinner, R. J. (2015). Nerves and Nerve Injuries: Vol 1: History, Embryology, Anatomy, Imaging, and Diagnostics (1st ed.). Academic Press.
3. Rea, P. (2016). Essential Clinically Applied Anatomy of the Peripheral Nervous System in the Head and Neck (1st ed.). Academic Press.