What is Clivus?: An Expert Overview of This Skull Base Structure

September 21, 2025 •

4 min read

Derived from the Latin word for “slope,” the clivus is a crucial bone at the center of your skull's base. It provides a vital protective boundary for the brainstem and is a central point for complex neurovascular pathways. Understanding what is Clivus and its role is key to comprehending several rare but significant medical conditions.

Quick Summary

The clivus is a central, sloping bone formed by the fusion of the sphenoid and occipital bones, located at the skull base and protecting the brainstem. Its central location makes it a hub for vital nerves and vessels, and it can be affected by various pathologies, including tumors like chordomas, demanding specialized, often multidisciplinary, medical attention.

Key Points

Location: The clivus is a central, sloping bone at the base of the skull, connecting the sphenoid and occipital bones.
Protection: Its primary role is to protect the brainstem and vital neurovascular structures, such as the basilar artery and abducens nerve.
Common Tumors: Chordomas and chondrosarcomas are among the most frequently occurring tumors in this region, though they are rare overall.
Symptoms: Pathologies can cause headaches, double vision (abducens nerve palsy), and other neurological deficits due to compression.
Diagnosis: Imaging via CT and MRI is essential for diagnosis, revealing the extent and nature of clival lesions.
Multidisciplinary Approach: Treatment often requires collaboration between neurosurgeons, ENT specialists, and oncologists due to the region's complexity.

What is the Clivus? An Anatomical Deep Dive

The clivus is a smooth, gentle bony surface located in the midline of the posterior cranial fossa. Its position is central and strategic, starting from behind the dorsum sellae of the sphenoid bone and sloping backward to the anterior edge of the foramen magnum, the large opening through which the spinal cord passes. Anatomically, it is formed by the complete fusion of two distinct bones: the basisphenoid (part of the sphenoid bone) and the basiocciput (part of the occipital bone). This fusion process typically completes by the time an individual reaches their late teens, creating a solid, protective structure.

The Critical Location and Relations of the Clivus

Because of its prime position at the intersection of several cranial fossae, the clivus has several critical anatomical relationships.

Brainstem: The clivus serves as a resting surface for the brainstem, which includes the pons and medulla oblongata, two crucial areas for regulating involuntary functions like breathing, heart rate, and consciousness.
Cranial Nerves: Several cranial nerves, most notably the abducens nerve (CN VI), run along or in close proximity to the clivus. Any pathology affecting the clivus can easily impact these nerves, leading to specific neurological symptoms.
Major Arteries: The basilar artery, a major vessel supplying blood to the brainstem and cerebellum, runs along the posterior surface of the clivus. The internal carotid arteries are also found laterally to the clivus.
Sphenoid Sinus: The clivus sits just posterior to the sphenoid sinuses, air-filled cavities within the skull.

Function and Protective Role

The primary function of the clivus is protective, acting as a sturdy bone shield for the brainstem and major blood vessels against trauma from the front of the skull. Its central and robust nature is vital for maintaining the integrity of these life-sustaining structures. As a boundary between the endocranial structures and the nasopharynx below, it serves as a foundational component of the posterior skull base. The integrity of the clivus is also an important landmark in anatomical alignment assessments, particularly for conditions affecting the craniovertebral junction.

Associated Pathologies and Medical Conditions

A wide range of pathologies, both benign and malignant, can affect the clivus, often presenting with symptoms due to the compression of nearby neurovascular structures.

Neoplastic Conditions (Tumors)

Chordoma: A rare, slow-growing tumor arising from remnants of the embryonic notochord. It is the most frequent primary clival tumor and is locally aggressive, with a high recurrence rate.
Chondrosarcoma: Another slow-growing malignancy that arises from cartilage. It often originates from the petroclival synchondrosis, a joint adjacent to the clivus, and is paramedian rather than midline.
Metastatic Disease: Cancers originating elsewhere in the body, such as from the prostate, kidney, breast, and lung, can metastasize to the clivus.
Other Tumors: Less common tumors include plasmacytoma, meningioma, and invasive pituitary adenomas that extend into the region.

Non-Neoplastic Conditions

Inflammatory and Infectious Conditions: This includes conditions like skull base osteomyelitis, often stemming from ear infections, and mucoceles originating in the sphenoid sinus that can erode the clivus.
Fibrous Dysplasia: A benign developmental disorder where normal bone is replaced by fibrous tissue.
Congenital Anomalies: Rare conditions like ecchordosis physaliphora, remnants of the notochord, can occur in the clivus.

Diagnosis and Treatment of Clival Lesions

Diagnosis of clival pathology relies on advanced imaging techniques, primarily computed tomography (CT) scans and magnetic resonance imaging (MRI). CT is excellent for visualizing bony detail and calcifications, while MRI provides superior soft tissue resolution, crucial for assessing the extent of the lesion and its impact on surrounding neural structures. Due to the rarity and complexity of these conditions, treatment is highly specialized and requires a multidisciplinary team, often including neurosurgeons, otorhinolaryngologists, oncologists, and neuroradiologists. Surgical approaches are complex and must be tailored to the specific lesion, with options including endoscopic transnasal and microsurgical transcranial techniques.

Comparison: Clivus vs. Sella Turcica

The clivus and sella turcica are both important bony structures at the base of the skull but have distinct locations and functions.


Feature	Clivus	Sella Turcica
Location	Midline, sloping bone behind the dorsum sellae, extending to the foramen magnum.	Bony depression within the sphenoid bone, behind the chiasmatic groove.
Primary Function	Protects the brainstem and major blood vessels.	Houses and protects the pituitary gland.
Associated Structures	Brainstem (pons, medulla), basilar artery, CN VI, cavernous sinus.	Pituitary gland, optic chiasm, cavernous sinus.
Associated Pathologies	Chordomas, chondrosarcomas, metastases, osteomyelitis.	Pituitary adenomas (tumors of the pituitary gland), Empty Sella Syndrome.

Conclusion

The clivus is a fundamentally important, though often overlooked, bone of the skull base, serving as a protective and central nexus for critical neurovascular structures. While typically a stable anatomical feature, its central location makes any associated pathology a serious concern, requiring expert diagnosis and a carefully planned, often intricate, treatment strategy. The field of skull base surgery continues to evolve, offering increasingly refined approaches for managing conditions affecting this complex region. For more information, you can consult sources like the Chordoma Foundation.

Frequently Asked Questions

The main function of the clivus is to provide a protective bony shield for the brainstem and other critical neural and vascular structures located in the posterior cranial fossa.

The clivus is located at the center of the skull base, stretching from the back of the sella turcica down to the foramen magnum. It is a fusion of the basiocciput and basisphenoid bones.

Yes, problems with the clivus can cause double vision, or diplopia. This is often due to a lesion compressing the abducens nerve (CN VI), which tracks along the clivus and controls lateral eye movement.

No, not all clival tumors are cancerous. While malignant tumors like chordomas and chondrosarcomas occur, benign conditions such as fibrous dysplasia and congenital cysts can also affect the area.

Diagnosis of clival lesions primarily involves advanced imaging techniques like MRI and CT scans. An MRI provides detailed soft tissue views, while a CT scan offers clear images of the bone itself.

The clivus is the central, sloping bone that protects the brainstem, while the sella turcica is a separate, saddle-shaped depression within the sphenoid bone that cradles the pituitary gland. They are located near each other but have distinct roles and locations.

A chordoma is a rare cancer that arises from embryonic notochord cells, which are often found as remnants along the midline of the skull and spine. Because the clivus develops from the notochord, it is a common site for chordomas to form.