Persistent hypophyseal canal

Persistent hypophyseal canal, also known when larger than 1.5mm in diameter as the craniopharyngeal canal, is a rare congenital defect characterised by a communication through the central skull base between the nasopharynx and the pituitary fossa

There are a number of terms which refer to this abnormality and some authors distinguish between canals greater or less than 1.5mm in diameter. To avoid confusion:

  • less than 1.5mm in diameter
    • persistent hypophyseal canal
  • greater than 1.5mm in diameter
    • craniopharyngeal canal
    • large craniopharyngeal canal
    • transphenoidal canal

The remainder of this article will refer to the defect as a persistent hypophyseal canal, recognizing that when large, alternative terms are preferable. 

Additionally it may be that the larger defects are more closely related to transsphenoidal meningoencephalocoeles than to persistent hypophyseal canals 2,4

The incident of persistent hypophyseal canals has been reported to be as high as 0.42% 1.  

In most cases, individuals with a persistent canal are asymptomatic. Possible presentations include 1-3:  

In addition many craniofacial anomalies have been reported, especially with the larger defects, including 4:

  1. optic apparatus 
    1. hypertelorism
    2. abnormal optic tracts
    3. malformed globes
  2. midfacial cleft and cleft lip and palate
  3. agenesis of the corpus callosum

The exact cause of these defects is uncertain, as is whether or not all are due tot he same underlying aetiology. Two theories have been proposed: 

  1. persistence of the Rathke's pouch
  2. persistence of a vascular channel

Persistent hypophyseal canals, and the larger craniopharyngeal canals, are found in the midline, oriented vertically extending form the floor of the pituitary fossa to the posterior wall of the nasopharynx, passing behind the sphenoid sinus. 

CT

They are best appreciated on thin slice bone algorithm CT, and appear as sharply circumscribed corticated canal. 

Head and neck anatomy
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Article information

rID: 25342
System: Head & Neck
Section: Anatomy
Tag: variant
Synonyms or Alternate Spellings:
  • Large craniopharyngeal canal
  • Craniopharyngeal canal
  • Transphenoidal canal

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