Foramen in the temporal bone of the skull
The stylomastoid foramen is a foramen between the styloid and mastoid processes of the temporal bone of the skull. It is the termination of the facial canal, and transmits the facial nerve, and stylomastoid artery. Facial nerve inflammation in the stylomastoid foramen may cause Bell's palsy.
Structure.
The stylomastoid foramen is between the styloid and mastoid processes of the temporal bone. The average distance between the opening of the stylomastoid foramen and the styloid process is around 0.7 mm or 0.8 mm in adults, but may decrease to around 0.2 mm during aging.
The stylomastoid foramen transmits the facial nerve, and the stylomastoid artery. These 2 structures lie directly next to each other.
Clinical significance.
Bell's palsy can result from inflammation of the facial nerve where it leaves the skull at the stylomastoid foramen. Patients with Bell's palsy appear with facial drooping on the affected side.
References.
 "This article incorporates text in the public domain from the 20th edition of" Gray's Anatomy "(1918)"