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Stylomastoid Foramen

foramen stylomastoideum

The stylomastoid foramen is the external opening of the facial canal (fallopian canal) on the inferior surface of the temporal bone, between the styloid process anteriorly and the mastoid process posteriorly. The facial nerve (CN VII) exits the temporal bone through this foramen to enter the parotid gland, where it divides into its five main branches. The stylomastoid artery (a branch of the posterior auricular) enters the canal here.

Region: Head & Skull

Clinical Relevance

Clinical Notes

The stylomastoid foramen is the landmark for surgical identification of the main trunk of the facial nerve in parotidectomy. The nerve is found by dissection between the tragal pointer (conchal cartilage) and the posterior belly of digastric, approximately 1 cm deep and slightly inferior to the stylomastoid foramen. Trauma, tumour, or infection at this level produces complete ipsilateral lower motor neurone facial palsy. In temporal bone surgery for otitis media, the facial nerve is protected throughout the facial canal as it descends vertically to this foramen.

Pathology

Common Injuries & Conditions

Facial Nerve Identification at Stylomastoid Foramen in Parotidectomy

The main trunk of the facial nerve is identified in parotidectomy at its exit from the stylomastoid foramen by tracing the tragal pointer to the stylomastoid region and dissecting between the posterior digastric and the cartilaginous landmark; nerve stimulation confirms identification before any tissue division in the parotid.