Third occipital nerve

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The third occipital nerve (TON) is a branch of the posterior root of C3, which provides cutaneous sensation to a small portion of the occipital scalp and innervates the C2/3 facet joints.

Gross anatomy

Location

Occipital region of the scalp close to the midline.

Origin

The posterior root of C3 (the third cervical nerve) gives off a medial branch which traces a path between the semispinalis capitis and cervicis muscles, before passing through the splenius capitis and trapezius muscles. Subjacent to the trapezius the medial branch gives off the third occipital nerve.

Course

The third occipital nerve runs as thin fibers vertically, medial to the greater occipital nerve , for a short distance, before passing laterally, crossing the greater occipital nerve and running as far as the retroauricular line, where there may be overlap with small twigs from the lesser occipital nerve. Vertically the fibers do not extend beyond the superior nuchal line.

Branches

There are no named branches of the third occipital nerve, however, multiple small twigs intercommunicate with branches of the greater occipital nerve. Far laterally, the branches may overlap with small twigs from the lesser occipital nerve.

Some of the branches transverse medially, across the midline, and intercommunicate with the contralateral third occipital nerve .

Supply

The third occipital nerve supplies an area of the medial occipital scalp, overlapping with areas supplied by the greater and lesser occipital nerves. It also supplies the C2/3 facet joints .

Clinical importance

Third occipital nerve blocks and/or neurolysis can be used for the treatment of third occipital headache .

Related pathology