Clivus – Anatomy, Diseases and Treatment
The clivus is a sloping bone structure at the skull base connecting the occipital bone to the sphenoid bone, housing important cranial nerves and blood vessels.
Things worth knowing about "Clivus"
The clivus is a sloping bone structure at the skull base connecting the occipital bone to the sphenoid bone, housing important cranial nerves and blood vessels.
Definition and Anatomy
The clivus (Latin for "slope" or "incline") is a sloping bony structure located at the inner surface of the skull base. It extends from the dorsum sellae (posterior part of the sella turcica in the sphenoid bone) to the foramen magnum (the large opening at the base of the skull) and is formed by two bones: the sphenoid bone in its upper portion and the occipital bone in its lower portion. The junction between these two bones is the sphenooccipital synchondrosis, which fuses by the end of puberty.
The clivus forms the ventral (anterior) boundary of the posterior cranial fossa and lies directly anterior to the brainstem (pons and medulla oblongata). On its surface run the basilar venous plexus and important cranial nerves, most notably the abducens nerve (cranial nerve VI).
Clinical Significance
Although the clivus is less commonly discussed in everyday clinical practice, it holds significant importance in neurosurgery, neuroradiology, and oncology. Due to its proximity to the brainstem and critical cranial nerves, diseases affecting the clivus can result in serious neurological consequences.
Diseases of the Clivus
Chordomas
Chordoma is the most common primary tumor of the clivus. It is a slow-growing but locally aggressive tumor arising from remnants of the embryonic notochord. Chordomas account for approximately 35% of all clival tumors. Typical symptoms include headaches, double vision (due to involvement of the abducens nerve), swallowing difficulties, and other cranial nerve deficits.
Chondrosarcomas
Chondrosarcomas are cartilaginous tumors that can also arise in the skull base region, including the clivus. They grow more slowly than other sarcomas but can cause significant neurological damage due to their location.
Meningiomas
Clival meningiomas are benign tumors of the meninges arising from the dura mater overlying the clivus. They grow slowly but can cause significant symptoms through compression of the brainstem and cranial nerves.
Other Conditions
- Metastases: The clivus can be a site of bone metastases, particularly from prostate, breast, or lung cancer.
- Clival fractures: Severe skull base fractures can involve the clivus and are associated with high mortality and serious neurological deficits.
- Ecchordosis physaliphora: A benign, non-tumorous accumulation of notochordal remnants, usually discovered incidentally on imaging.
Symptoms of Clival Diseases
Symptoms depend on the specific condition and the degree of involvement of adjacent structures. Common complaints include:
- Persistent headaches, especially in the occipital region
- Double vision (diplopia) due to abducens nerve involvement
- Swallowing difficulties (dysphagia) and hoarseness
- Facial numbness
- Gait disturbances and coordination problems (cerebellar or brainstem involvement)
- Neck pain and stiffness
Diagnosis
Diagnosis of clival diseases is primarily achieved through imaging:
- MRI (Magnetic Resonance Imaging): The preferred method for evaluating soft tissue tumors, brainstem involvement, and cranial nerve infiltration.
- CT (Computed Tomography): Useful for assessing bone destruction and calcifications.
- Biopsy: Required for histological confirmation of the diagnosis in cases of unclear tumor type.
Treatment
Treatment depends on the type of disease:
- Surgical resection: For tumors such as chordomas or meningiomas, complete surgical removal is the primary treatment goal. Due to the challenging anatomical location, this is technically demanding and requires specialized neurosurgical expertise (e.g., endoscopic endonasal or transoral approaches).
- Radiation therapy: In particular, proton therapy or carbon ion therapy are used for chordomas and chondrosarcomas due to their high precision and ability to spare surrounding brain tissue.
- Chemotherapy: For certain tumors (e.g., metastatic disease), systemic therapy may be required.
References
- Standring S. (Ed.) - Gray's Anatomy: The Anatomical Basis of Clinical Practice, 41st Edition, Elsevier, 2015.
- Almefty K., Pravdenkova S., Colli B.O. et al. - Chordoma and chondrosarcoma: similar, but quite different, skull base tumors. Cancer, 2007; 110(11): 2457-2467. PubMed PMID: 17924479.
- Neff B., Sataloff R.T. - Tumors of the Skull Base. In: Cummings Otolaryngology, 7th Edition, Elsevier, 2021.
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