Location of the Inferior Petrosal Sulcus
The inferior petrosal sulcus is found on the intracranial (superior) surface of the basilar part of the occipital bone and extends onto the posterior surface of the petrous part of the temporal bone.
- On the basilar part (Pars basilaris): The basilar part lies anterior to the foramen magnum (Foramen magnum). The midline features the clivus (Clivus), with the inferior petrosal sulcus positioned laterally to it.
- On the petrous temporal bone (Pars petrosa): The sulcus continues onto the posterior surface of the petrous pyramid. The apex of the petrous part (Apex partis petrosae) points forward and medially, while its base is directed posteriorly and laterally.
Topography and Adjacent Structures
On the posterior surface of the petrous temporal bone, alongside the inferior petrosal sulcus, are:
- The internal acoustic opening (Porus acusticus internus), leading into the internal acoustic meatus (Meatus acusticus internus).
- The subarcuate fossa (Fossa subarcuata).
- The apertura of the vestibular canaliculus (Apertura canaliculi vestibuli), leading into the vestibular canaliculus (Canaliculus vestibuli).
On the external (inferior) surface of the basilar part, along the midline near the pharyngeal attachment, lies the pharyngeal tubercle (Tuberculum pharyngeum).
Relationship with the Petro-Occipital Fissure
The petro-occipital fissure (Fissura petrooccipitalis) lies between the occipital and temporal bones. On a macerated skull, this fissure is visible at the level of the Sulcus sinus petrosi inferioris. The jugular foramen (Foramen jugulare) is also located between the occipital and temporal bones.
Relation to the Posterior Cranial Fossa
Boundaries of the posterior cranial fossa:
- Anterior boundary: Laterally by the superior border of the petrous part (Margo superior partis petrosae) or the superior petrosal sulcus (Sulcus sinus petrosi superioris); in the midline by the dorsum sellae (Dorsum sellae) of the sphenoid body.
- Posterior boundary: In the midline by the cruciform eminence (Eminentia cruciformis) or internal occipital protuberance (Protuberantia occipitalis interna); laterally by the transverse sulcus (Sulcus sinus transversi).
Openings connecting the posterior cranial fossa to the external skull base and inner ear include:
- In the occipital bone: foramen magnum (Foramen magnum), condylar canal (Canalis condylaris), hypoglossal canal (Canalis nervi hypoglossi).
- In the temporal bone: mastoid foramen (Foramen mastoideum).
- To the inner ear cavities: apertura of the vestibular canaliculus (Apertura canaliculi vestibuli) and apertura of the cochlear canaliculus (Apertura canaliculi cochleae).
Adjacent Surfaces of the Petrous Part
The petrous pyramid encloses the tympanic cavity (Cavitas tympani) of the middle ear.
- Anterior surface: Features the trigeminal impression (Impressio trigeminalis), arcuate eminence (Eminentia arcuata), tegmen tympani (Tegmen tympani), and superior petrosal sulcus.
- Inferior surface: Features the jugular notch (Incisura jugularis) with the intrajugular process (Processus intrajugularis), jugular fossa (Fossa jugularis), styloid process (Processus styloideus), and external opening of the carotid canal (Apertura externa canalis carotici). The stylomastoid foramen (Foramen stylomastoideum) lies between the styloid and mastoid processes.
The base of the pyramid transitions into the mastoid process (Processus mastoideus), which is directed posteriorly and laterally and is bounded by the occipital margin (Margo occipitalis).
Grammatical Features of the Term
In Latin anatomical nomenclature, Sulcus sinus petrosi inferioris is classified as a complex term with a non-concordant modifier. The head noun sulcus is modified by a noun in the genitive case (Genitivus) — sinus petrosi inferioris (of the inferior petrosal sinus).