Location and Anatomical Borders
- The clivus is situated on the intracranial (superior) surface of the basilar part (pars basilaris).
- The basilar part lies anterior to the foramen magnum.
- The clivus is angled toward the ventral surface of the brainstem.
- Laterally, it is bordered by the sulcus for the inferior petrosal sinus (sulcus sinus petrosi inferioris), which continues onto the petrous part of the temporal bone.
- On the opposite, external (inferior) surface of the basilar part along the midline lies the pharyngeal tubercle (tuberculum pharyngeum), which serves as the attachment site for the pharyngeal raphe.
Vascular Relations
- After exiting the carotid canal, the internal carotid artery courses rostrally along the clivus to reach the cavernous sinus deep to the dura mater.
- Within the cavernous sinus, the artery curves posteriorly and superiorly, forming the carotid siphon (a posteriorly directed loop).
- The dura mater over the clivus is supplied by tiny extradural branches of the internal carotid artery. These same branches also supply the floor of the tympanic cavity, the trigeminal ganglion (gasserian ganglion), and the pituitary gland.
Neural Relations
- The clivus serves as a topographical landmark along the pathway of several cranial nerves, specifically cranial nerves III, IV, and VI.
- These nerves travel through or within the lateral wall of the cavernous sinus in close proximity to the internal carotid artery before entering the orbital cavity via the superior orbital fissure (fissura orbitalis superior).
Clinical Note: Other Anatomical Structures Named 'Slopes' (*Clivus* equivalents)
In medical literature, slope-like or inclined surfaces of other facial and jaw structures are occasionally referred to by similar descriptive terms in local terminology:
- Slopes of the articular tubercle — structures of the temporomandibular joint (TMJ). During the second phase of mouth opening, the articular disc and mandibular condyle glide anteriorly and inferiorly down the posterior slope of the articular tubercle, moving the condylar process forward by about 12 mm. In TMJ dislocation, the condylar head translates far forward past the articular tubercle.
- Slopes of the pterygomandibular fold (plica pterygomandibularis) — the lateral slope of this fold forms a groove with the cheek that serves as a landmark for needle insertion during inferior alveolar nerve blocks (such as the torusal technique).
- Lateral slopes of the nose — relevant in traumatology and reconstructive surgery: lateral impact causes depression of the ipsilateral nasal slope and displacement of the contralateral slope; firm gauze bolsters are often applied to the nasal slopes at the conclusion of rhinoplasty.
- Oral slope of the alveolar process — a prosthodontic term referring to the lingual/palatal incline of the alveolar process used as a guide for shaping wire frameworks in removable denture bases.