Abscess related to sternocleidomastoid is

Bezold abscess It can occur following acute coalescent mastoiditis when pus breaks through the thin medial side of the tip of the mastoid and presents as a swelling in the upper pa of neck. The abscess may (i) lie deep to sternocleidomastoid, pushing the muscle outwards, (ii) follow the posterior belly of digastric and present as a swelling between the tip of mastoid and angle of jaw, (iii) be present in upper pa of posterior triangle, (iv) reach the parapharyngeal space or (v) track down along the carotid vessels Ref: https://en.m.wikipedia.org/wiki/Bezold%27s_abscess