Canalis basilaris medianus
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Citation:
Gaillard F, Deng F, Sharma R, et al. Canalis basilaris medianus. Reference article, Radiopaedia.org (Accessed on 22 Mar 2025) https://doi.org/10.53347/rID-25161
rID:
25161
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Disclosures:
At the time the article was created Frank Gaillard had no recorded disclosures.
View Frank Gaillard's current disclosures
Last revised:
Disclosures:
At the time the article was last revised Francis Deng had no recorded disclosures.
View Francis Deng's current disclosures
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Synonyms:
- Canalis basilaris medianus (CBM)
- Inferior median clival canal
- Clival canal
- Median basal canal
- Median clival canal
The canalis basilaris medianus (median basal canal), also known as clival canal, median clival canal, or inferior median clival canal, refers to a number of anatomic variant midline canals in the clivus, typically involving the basioccipital portion.
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Gross anatomy
These canals are generally well-defined, corticated structures, usually less than 2 mm in diameter, that course through the clivus in the sagittal plane (occasionally diagonally).
Six types or variants of the canalis basilaris medianus have been described, divided into two groups 1,6:
-
complete (multiple openings in the clivus)
- canalis basilaris medianus superior: two openings on the dorsal (intracranial) surface
- canalis basilaris medianus inferior: one opening on the dorsal surface and another on the ventral (nasopharyngeal) surface
- canalis basilaris medianus bifurcatus: two openings on the dorsal surface and one opening on the ventral surface
-
incomplete (blind-ending canals or deep recesses in the clivus)
- long channel running through the basiocciput and posterior basisphenoid: one opening on the dorsal surface of the clivus with the blind end terminating posterior/inferior to the sella turcica
- superior recess in basiocciput: short, blind-ending opening on the dorsal surface
- inferior recess in basiocciput or large/deep foveola pharyngica (pharyngeal fossa): short, blind-ending opening on the ventral surface
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Variant anatomy
The prevalence of this variant is 1–5% 2-7.
It should not be confused with a horizontal groove or canal, which is sometimes seen thought to represent a venous channel between the inferior petrosal sinuses or a remnant of the first true somite 14.
Development
The canalis basilaris medianus is generally thought to represent a remnant of the notocord. However, some studies of the contents have found no notochordal structures but only venous channels emanating from the basilar plexus 7.
History and etymology
Canalis basilaris medianus was first described by Gruber in 1880 8, but it remains not well known. It is not included in Terminologia Anatomica. In 1987, Zhang and Yen asserted they were the first to describe such canals and termed them inferior median clival canals 5.
Related pathology
This anatomic variant is generally considered of no clinical significance 6, but some pathologies have rarely been reported in association:
- chordoma 9
- nasopharyngeal cystic structure, which may represent an enterogenous cyst 10, meningocele 13,15, or other cystic mimic of Tornwaldt cyst 11
- cerebrospinal fluid leak/rhinorrhoea 12
- meningitis 13,15
References
- 1. Currarino G. Canalis basilaris medianus and related defects of the basiocciput. AJNR Am J Neuroradiol. 1988;9 (1): 208-11. Pubmed citation
- 2. Paraskevas GK, Tsitsopoulos PP, Ioannidis OM. Incidence and purpose of the clival canal, a "neglected" skull base canal. (2013) Acta neurochirurgica. 155 (1): 139-40. doi:10.1007/s00701-012-1570-3 - Pubmed
- 3. Madeline LA, Elster AD. Postnatal development of the central skull base: normal variants. (1995) Radiology. 196 (3): 757-63. doi:10.1148/radiology.196.3.7644640 - Pubmed
- 4. Bayrak S, Göller Bulut D, Orhan K. Prevalence of anatomical variants in the clivus: fossa navicularis magna, canalis basilaris medianus, and craniopharyngeal canal. (2019) Surgical and radiologic anatomy : SRA. 41 (4): 477-483. doi:10.1007/s00276-019-02200-3 - Pubmed
- 5. Zhang WH, Yen WC. A new bony canal on the clival surface of the occipital bone. (1987) Acta anatomica. 128 (1): 63-6. Pubmed
- 6. Jacquemin C, Bosley TM, al Saleh M et-al. Canalis basilaris medianus: MRI. Neuroradiology. 2000;42 (2): 121-3. Pubmed citation
- 7. Tubbs RS, Griessenauer CJ, Loukas M, Zurada A, Shoja MM, Cohen-Gadol AA. The enigmatic clival canal: anatomy and clinical significance. (2010) Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery. 26 (9): 1207-10. doi:10.1007/s00381-010-1100-7 - Pubmed
- 8. Gruber W. Over the canalis basilaris medianus anomalies of the occipital bone in humans. Mem Acad Imp Sci St-Petersburg 1880:ser VII, tome 27, No.9.
- 9. Nguyen RP, Salzman KL, Stambuk HE et-al. Extraosseous chordoma of the nasopharynx. AJNR Am J Neuroradiol. 2009;30 (4): 803-7. AJNR Am J Neuroradiol (full text) - doi:10.3174/ajnr.A1446 - Pubmed citation
- 10. Morabito R, Longo M, Rossi A, Nozza P, Granata F. Pharyngeal enterogenous cyst associated with canalis basilaris medianus in a newborn. (2013) Pediatric radiology. 43 (4): 512-5. doi:10.1007/s00247-012-2513-0 - Pubmed
- 11. Lohman BD, Sarikaya B, McKinney AM et-al. Not the typical Tornwaldt's cyst this time? A nasopharyngeal cyst associated with canalis basilaris medianus. Br J Radiol. 2011;84 (1005): e169-71. Br J Radiol (full text) - doi:10.1259/bjr/95083086 - Free text at pubmed - Pubmed citation
- 12. Khairy S, Almubarak AO, Aloraidi A, Alahmadi KOA. Canalis basalis medianus with cerebrospinal fluid leak: rare presentation and literature review. (2019) British journal of neurosurgery. 33 (4): 432-433. doi:10.1080/02688697.2017.1346173 - Pubmed
- 13. Ko AL, Gabikian P, Perkins JA, Gruber DP, Avellino AM. Endoscopic repair of a rare basioccipital meningocele associated with recurrent meningitis. (2010) Journal of neurosurgery. Pediatrics. 6 (2): 188-92. doi:10.3171/2010.5.PEDS09346 - Pubmed
- 14. Nayak SR, Saralaya VV, Prabhu LV, Pai MM, Krishnamurthy A. Clinical significance of a mysterious clival canal. (2007) Romanian journal of morphology and embryology = Revue roumaine de morphologie et embryologie. 48 (4): 427-9. Pubmed
- 15. Martinez CR, Hemphill JM, Hodges FJ, Gayler BW, Nager GT, Long DM, Freeman JM. Basioccipital meningocele. (1981) AJNR. American journal of neuroradiology. 2 (1): 100-2. Pubmed
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