Inferior median clival canal

The inferior median clival canal also known as the canalis basilaris medianus is a rare anatomical variant of the clivus, which passes in the sagittal plane from the intracranial surface of the clivus to its retropharyngeal surface. It is generally thought to represent a remnant of the notocord

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 4

Radiographic features

The canal is a well-defined corticated structure, usually less than 2 mm in diameter which passes in the sagittal plane from the intracranial surface of the clivus (above the anterior rim of the foramen magnum) forwards and usually downwards to the nasopharyngeal surface (not surprisingly to the location of Tornwaldt cysts, also of notochord origin) 3. A co-existing cystic structure at its nasopharyngeal end has been reported, which may or may not represent a Tornwaldt cyst, depending on the definition 3.

Amazingly enough for a usually asymptomatic and rare anatomical variant, six subtypes have been described, divided into two groups 6,7

  • complete
    • superior
    • inferior
    • bifurcated (bifurcatus)
  • incomplete
    • a long channel running through the basiocciput and posterior sphenoid
    • a superior recess within the basiocciput  (blind ending recess on the intracranial surface)
    • an inferior foveola pharyngica recess (blind ending recess on the nasopharyngeal surface)

History and etymology

It was first described by Gruber in 1880 3,5

Anatomy: Head and neck

Anatomy: Head and neck

Article information

rID: 25161
System: Head & Neck
Section: Anatomy
Tag: variant
Synonyms or Alternate Spellings:
  • Canalis basilaris medianus

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