The clivus (,

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

for "slope"), or Blumenbach clivus, is a bony part of the

cranium The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

at the base of the

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

. It is a shallow depression behind the

dorsum sellae The dorsum sellae is part of the sphenoid bone in the skull. Together with the basilar part of the occipital bone it forms the clivus. In the sphenoid bone, the anterior boundary of the sella turcica is completed by two small eminences, one on e ...

of the

sphenoid bone The sphenoid bone is an unpaired bone of the neurocranium. It is situated in the middle of the skull towards the front, in front of the basilar part of occipital bone, basilar part of the occipital bone. The sphenoid bone is one of the seven bones ...

. It slopes gradually to the anterior part of the basilar

occipital bone The occipital bone () is a neurocranium, cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobe ...

at its junction with the

. It extends to the

foramen magnum The foramen magnum ( la, great hole) is a large, oval-shaped opening in the occipital bone of the skull. It is one of the several oval or circular openings (foramina) in the base of the skull. The spinal cord, an extension of the medulla oblon ...

. It is related to the

pons The pons (from Latin , "bridge") is part of the brainstem that in humans and other bipeds lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum. The pons is also called the pons Varolii ("bridge of Va ...

and the

abducens nerve The abducens nerve or abducent nerve, also known as the sixth cranial nerve, cranial nerve VI, or simply CN VI, is a cranial nerve in humans and various other animals that controls the movement of the lateral rectus muscle, one of the extraocula ...

(CN VI).

Structure

The clivus is a shallow depression behind the

of the

. It slopes gradually to the anterior part of the basilar

at its junction with the

. Synchondrosis of these two bones forms the clivus. The clivus extends inferiorly to the

. On axial planes, it sits just posterior to the

sphenoid sinus The sphenoid sinus is a paired paranasal sinus occurring within the within the body of the sphenoid bone. It represents one pair of the four paired paranasal sinuses.Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, ...

es. It is medial to the

foramen lacerum The foramen lacerum ( la, lacerated piercing) is a triangular hole in the base of skull. It is located between the sphenoid bone, the apex of the petrous part of the temporal bone, and the basilar part of the occipital bone. Structure The for ...

(the

internal carotid artery The internal carotid artery (Latin: arteria carotis interna) is an artery in the neck which supplies the anterior circulation of the brain. In human anatomy, the internal and external carotids arise from the common carotid arteries, where these b ...

reaches the middle cranial fossa above the foramen lacerum), proximal to its anastomosis with the

Circle of Willis The circle of Willis (also called Willis' circle, loop of Willis, cerebral arterial circle, and Willis polygon) is a circulatory anastomosis that supplies blood to the brain and surrounding structures in reptiles, birds and mammals, including huma ...

. It is anterior to the

basilar artery The basilar artery () is one of the arteries that supplies the brain with oxygen-rich blood. The two vertebral arteries and the basilar artery are known as the vertebral basilar system, which supplies blood to the posterior part of the circle of W ...

. On sagittal plane, it can be divided into two surfaces including the pharyngeal (inferior) surface and basilar (superior) surface. A small elevation known as the

pharyngeal tubercle The pharyngeal tubercle is a part of the occipital bone of the head and neck. It is located on the lower surface of the basilar part of occipital bone. It is the site of attachment of the pharyngeal raphe. Structure The pharyngeal tubercle is l ...

is present on the inferior surface for the fibrous raphe of pharynx to attach. The

sits on the basilar surface of the clivus. The

(CN VI) also tracks along the clivus during its course.

Variations

During embryonic development, the clivus is formed by the fusion of the basiocciput and basisphenoid or also known as the sphenooccipital

synchondrosis A synchondrosis (or primary cartilaginous joint) is a type of cartilaginous joint where hyaline cartilage completely joins together two bones. Synchondroses are different than symphyses (secondary cartilaginous joints) which are formed of fibroc ...

. When the fusion occurs improperly, it would give rise to gaps that are considered anatomical variations. Variations of the clivus include

fossa navicularis magna Fossa navicularis magna (also known as ''pharyngeal fossa'' or ''phyaryngeal fovela'') is a variant bony depression found at the midline of the occipital part of clivus. This fossa was first described by Tourtual. Its prevalence ranges from 0.9 to ...

craniopharyngeal canal The craniopharyngeal canal is a human anatomical feature sometimes found in the sphenoid bone opening to the sella turcica. It is a canal (a passage or channel) sometimes found extending from the anterior part of the fossa hypophyseos of the spheno ...

, canalis basilaris medianus, and transverse basilar fissure (Saucer's fissure).

Ossification Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in t ...

of the

apical ligament of dens The ligament of apex dentis (or apical odontoid ligament) is a ligament that spans between the second cervical vertebra in the neck and the skull. It lies as a fibrous cord in the triangular interval between the alar ligaments, which extends fro ...

may also occur, resulting in a variant bony tubercle at the inferior end of the clivus. Condylus tertius and arcus praebasiocipitalis are the other two variations that can be found at the lower end of the clivus, although their etiology may be different from the other variations. Ecchordosis physaliphora, a congenital benign lesion derived from the notochord, might be present in the dorsal part of the clivus. This lesion is harmless is considered an anatomical variant.

Clinical importance

The

(CN VI) tracks along the clivus during its course. Increased

intracranial pressure Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury (mmHg) and at rest, is normally 7–15 Millimeter of mercury, mmHg ...

can trap the nerve at this point and cause signs of

palsy Palsy is a medical term which refers to various types of paralysisDan Agin, ''More Than Genes: What Science Can Tell Us About Toxic Chemicals, Development, and the Risk to Our Children;; (2009), p. 172. or paresis, often accompanied by weakness and ...

. The clivus is also the site for

chordoma Chordoma is a rare slow-growing neoplasm thought to arise from cellular remnants of the notochord. The evidence for this is the location of the tumors (along the neuraxis), the similar immunohistochemical staining patterns, and the demonstration ...

, a rare type of

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

Surgery

Surgery for lesions involving the clivus and surrounding structures have traditionally been approached via extended subfrontal transbasal, anterior transfacial, lateral transtemporal, far-lateral approaches, and staged approaches. These approaches are limited in that they often require extensive bone removal and brain retraction while placing critical neurovascular structures between the surgeon and the site of pathology. It has been proposed that these limitations are mitigated by significant advancements in the use of

endoscopic endonasal surgery Endoscopic endonasal surgery is a minimally invasive technique used mainly in neurosurgery and otolaryngology. A neurosurgeon or an otolaryngologist, using an endoscope that is entered through the nose, fixes or removes brain defects or tumors in ...

. Contemporary surgical approaches involving extended endoscopic endonasal approaches to the clivus have been increasingly described by several groups, and have been shown to be a safe and effective strategy for the surgical management of a variety of benign and malignant lesions.

Relation of the clivus and dens

The clivus is an important landmark for checking for anatomical atlanto-occipital alignment. When viewed on a lateral

C-spine In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In ...

radiograph Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeut ...

, the clivus forms a line which, if extended, is known as ''Wackenheim's clivus line''. ''Wackenheim's clivus line'' should pass through the dens of the

axis An axis (plural ''axes'') is an imaginary line around which an object rotates or is symmetrical. Axis may also refer to: Mathematics * Axis of rotation: see rotation around a fixed axis *Axis (mathematics), a designator for a Cartesian-coordinate ...

or be tangential to it.McKenna DA, Roche CJ, Lee KW, Torreggiani WC, Duddalwar VA. Atlanto-occipital dislocation: case report and discussion. ''Can J Emerg Med'' 2006; 8(1):50-3. Available at
link
an
link
. Accessed on: December 7, 2006.

History

"Clivus" is also used as an abbreviated term for the clivus ocularis, which is the sloping inner wall of the

retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...

as it dips into the

foveola The foveola is located within a region called the macula, a yellowish, cone photoreceptor filled portion of the human retina. Approximately 0.35 mm in diameter, the foveola lies in the center of the fovea and contains only cone cells and a co ...

in the

macula The macula (/ˈmakjʊlə/) or macula lutea is an oval-shaped pigmented area in the center of the retina of the human eye and in other animals. The macula in humans has a diameter of around and is subdivided into the umbo, foveola, foveal avas ...

of the eye. To disambiguate, the clivus is sometimes referred to as the Blumenbach clivus. This is named after

Johann Friedrich Blumenbach Johann Friedrich Blumenbach (11 May 1752 – 22 January 1840) was a German physician, naturalist, physiologist, and anthropologist. He is considered to be a main founder of zoology and anthropology as comparative, scientific disciplines. He wa ...

Additional images

File:Slide12jjjj.JPG, Clivus File:Slide6pppp.JPG, Clivus

References

External links

* - "Osteology of the Skull: Internal Surface of Skull"
Diagram at uwo.ca
{{Authority control Bones of the head and neck

Structure

Variations

Clinical importance

Surgery

Relation of the clivus and dens

History

Additional images

See also

References

External links