Side of temporal bone is determined by:
- Mastoid tip points downwards
- Zygomatic process will point anterior and is placed on the lateral aspect.
- Squamous part is directed superiorly.
- Petrous apex points medially and anteriorly.
Parts of temporal bone:
- Tympanic bone
- Mastoid process
- Squamous part
- Petrous part
Note: styloid process is not considered a part of temporal bone.
LATERAL SURFACE (FIG. 1.1)
Landmarks found after reflecting of the soft tissue.
- Zygomatic process (Z).
- Temporal line (linea temporalis) (red line)—Defines the inferior border of the temporalis muscle and also approximates the position of the floor of the middle cranial fossa.
- Squamous portion (S) of the temporal bone.
- Mastoid (M)—Posteriorly.
- Spine of Henle (H)—is at posterior-superior rim of external auditory canal.
- Macewen's triangle (Mt) the fossa mastoidea – overlies the mastoid antrum:
- Temporal line superiorly
- Tangent to the posterior external auditory canal posteriorly
- Posterosuperior rim of the canal.
- Tip of the mastoid process (MT).
- Tympanomastoid fissure (TMF)—Anterior to the tip of the mastoid and can be traced medially to the stylomastoid foramen, which is the exit point of the facial nerve.
- Tympanic ring (TR).
- Tympanosquamous suture (TSS)—Anterosuperior part of the ring, in external auditory canal.
- Glenoid fossa (G)—Anteriorly, lies beneath the root of the zygoma.
SUPERIOR SURFACE (FIG. 1.2)
The superior surface (tegmen) of the temporal bone forms the floor of middle cranial fossa. The tegmen can be divided into:
- Tegmen tympani (forming the roof of tympanic cavity).
- Tegmen mastoidale (forming the roof of mastoid air cells).
- Petrotympanic suture line—Medial boundary of the tegmen.
Other structures seen on superior surface are:
- Arcuate eminence (85%)—Approximates the position of the superior semicircular canal (SSCC)
- Gasserian (semilunar) ganglion
- Greater petrosal nerve (GPN) runs parallel to the petrous ridge.
- From medial to lateral, are:
- Foramen ovale (mandibular division of the trigeminal nerve)
- Foramen spinosum (middle meningeal vessels and a recurrent branch of the mandibular nerve)
- Superior petrosal sinus.
- Foramen lacerum—False foramen filled with fibrous connective tissue, forms the roof of the carotid canal, found at the junction of
- Base of the greater wing of the sphenoid,
- Petrous apex, and
- Basiocciput,
POSTERIOR SURFACE (FIG. 1.3)
It forms the anterior border of the posterior cranial fossa
- Sigmoid sulcus (S)—For sigmoid sinus
- Foveate fossa (E) for intradural portion of the endolymphatic sac.
- Operculum covers the intraosseous portion of the endolymphatic sac.
- Vestibular aqueduct.
- Internal auditory canal (C)—Runs anteromedially to posterolaterally, and contains the cochlear, vestibular, and facial nerves, along with their blood supply.
- Superior petrosal sulcus (P)—Carries the superior petrosal sinus from the sigmoid sinus to the cavernous sinus.
INFERIOR SURFACE (FIG. 1.4)
It separates the upper neck from the skull base.
- Carotid foramen (C)—Internal carotid artery enters the temporal bone.
- Jugulocarotid crest—Separates the carotid canal from the jugular foramen.
- Jugular foramen (J).
- Styloid process (S)—Lateral to the jugular foramen.
- Stylomastoid foramen (F)—Posterior to the styloid process.
- Digastric groove (D)—Medial to the mastoid tip, for the posterior belly of the digastric muscle.
- Inferior tympanic canaliculus for Inferior tympanic artery (a branch of the ascending pharyngeal artery) and tympanic branch of glossopharyngeal nerve (Jacobson's nerve) is present in the Jugulocarotid crest.
- Aperture of cochlear aqueduct is anteromedial to the jugular fossa.
ANTERIOR SURFACE (FIG. 1.5)
- Internal carotid foramen.
- The impression for the trigeminal ganglion is located on the lateral surface of the petrous apex.
- Canal for the tensor tympani is lateral to the carotid canal.
- Bony portion of the Eustachian tube—Inferior and parallel to tensor tympani muscle.
