The mastoid process is the conical bony projection of the mastoid part of the temporal bone, lying posterior and inferior to the external auditory meatus. Its external surface gives attachment to the sternocleidomastoid, splenius capitis, and longissimus capitis muscles. Internally it is honeycombed by air cells (mastoid air cells) that communicate with the middle ear via the mastoid antrum. The facial nerve exits the stylomastoid foramen at its medial base.
| Articulations | |
|---|---|
| Landmarks |
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| Ossification | Develops from the petrous part of the temporal bone after birth; the process is absent in the newborn and grows during the first two years as the sternocleidomastoid pulls on it and mastoid air cells form. |
Mastoiditis is a potentially life-threatening complication of acute otitis media where infection spreads from the middle ear into the mastoid air cells, producing retroauricular swelling, erythema, and forward displacement of the pinna. Untreated mastoiditis can spread to cause meningitis, epidural abscess, or sigmoid sinus thrombosis. The mastoid process is a surgical landmark in posterior fossa approaches and parotidectomy, where the facial nerve exits at the stylomastoid foramen just medial to its base. Mastoidectomy is the cornerstone procedure for cholesteatoma and chronic suppurative otitis media.
Place a fingertip directly behind the ear lobe. The rounded bony bulge pointing downward is the mastoid process; follow it down to its tip, where the sternocleidomastoid tendon attaches. Turning the head to the opposite side makes the muscle stand out and leads you to it.
Bacterial spread from acute otitis media into the mastoid air cells produces retroauricular pain, erythema, and pinna displacement with a sagging posterior ear canal on otoscopy, treated urgently with intravenous antibiotics and cortical mastoidectomy to drain the infected cells and prevent intracranial complications.
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