Persistent hypophyseal canal
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Persistent hypophyseal canal, also known as the craniopharyngeal canal when larger than 1.5 mm in diameter, is a rare congenital defect characterized by communication through the central skull base between the nasopharynx and the pituitary fossa.
There are a number of terms that refer to this abnormality and some authors distinguish between canals based on whether they are larger or smaller than 1.5 mm in diameter. To avoid confusion:
a canal less than 1.5 mm in diameter
persistent hypophyseal canal
a canal greater than 1.5 mm in diameter
large craniopharyngeal canal
The persistent craniopharyngeal canal can also be divided into the following subtypes 5:
type 1: incidentally detected thin persistent craniopharyngeal canal
type 2: persistent craniopharyngeal canal with ectopic adenohypophysis
type 3A: with cephalocele
type 3B: with tumor
type 3C: with both
The remainder of this article will refer to the defect as a persistent hypophyseal canal, keeping in mind that when large, alternative terms are preferable.
Additionally, the larger defects are possibly more closely related to transsphenoidal meningoencephaloceles than to persistent hypophyseal canals 2,4.
The prevalence 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:
pituitary gland prolapsing into nasopharynx 2
In addition, many craniofacial anomalies have been reported, especially with the larger defects, including 4:
midfacial cleft and cleft lip and palate
The exact cause of these defects is uncertain, as is whether or not they all share the same underlying etiology. Two theories have been proposed:
persistence of Rathke's pouch
persistence of a vascular channel
Persistent hypophyseal canals, as well as the larger craniopharyngeal canals, are found in the midline, oriented vertically and extending from the floor of the pituitary fossa to the posterior wall of the nasopharynx, passing behind the sphenoid sinus.
They are best appreciated on thin slice bone filter CT and appear as a sharply circumscribed corticated canal.
- 1. Hughes ML, Carty AT, White FE. Persistent hypophyseal (craniopharyngeal) canal. Br J Radiol. 1999;72 (854): 204-6. Br J Radiol (abstract) - Pubmed citation
- 2. Ekinci G, Kiliç T, Baltacioğlu F et-al. Transsphenoidal (large craniopharyngeal) canal associated with a normally functioning pituitary gland and nasopharyngeal extension, hyperprolactinemia, and hypothalamic hamartoma. AJR Am J Roentgenol. 2003;180 (1): 76-7. doi:10.2214/ajr.180.1.1800076 - Pubmed citation
- 3. Hooper AC. Sphenoidal defects-a possible cause of cerebrospinal fluid rhinorrhoea. J. Neurol. Neurosurg. Psychiatr. 1972;34 (6): 739-42. Free text at pubmed - Pubmed citation
- 4. Currarino G, Maravilla KR, Salyer KE. Transsphenoidal canal (large craniopharyngeal canal) and its pathologic implications. AJNR Am J Neuroradiol. 1985;6 (1): 39-43. Pubmed citation
- 5.Craniopharyngeal Canal and Its Spectrum of Pathology T.A. Abele, K.L. Salzman, H.R. Harnsberger, C.M. Glastonbury American Journal of Neuroradiology Apr 2014, 35 (4) 772-777; DOI: 10.3174/ajnr.A3745