Canalis basilaris medianus: MRI

Abstract

We report the MRI appearances of an developmental anatomical variant of the basiocciput, with neuroimaging findings (CT and MRI). Such variants are commonly asymptomatic, but may be associated with episodes of meningitis.

Fossa navicularis: Anatomic variation at the skull base

“…Collins (1928) referred to it as the fossa pharyngea, whereas Currarino (1988) used the term "canalis basilaris medianus." In recent publications by Beltramello et al (1998) and Jacquemin et al (2000), the terms "fossa navicularis magna" and "large pharyngeal fossa" are used, respectively. Both of these publications reported the defects to be filled with lymphoid tissue.…”

Imaging of nasopharyngeal cysts and bursae

“…3) [11]. Some authors consider this fossa to be an incomplete and lower form of a canalis basilaris medianus [12]. The few observations of fossa navicularis analyzed in MRI show that the latter can be filled by pharyngeal tissue [11,12].…”

Not the typical Tornwaldt's cyst this time? A nasopharyngeal cyst associated with canalis basilaris medianus

“…It is thought to represent an embryological remnant demarcating the cephalic end of the notochord (a midline collection of cells that aids embryonic long-axis and neural plate development) and corresponds to the course of the notochordal canal in the caudal basiocciput [1,3]. Several variants of CBM have been described, namely six subtypes: a complete CBM that includes superior, inferior and bifurcatus forms; and an incomplete CBM that includes a long channel running through the basiocciput and posterior sphenoid, a superior recess within the basiocciput and an inferior ''foveola pharyngica'' recess [2,4]. A complete CBM traverses entirely through the basioccipital bone, while an incomplete CBM can extend partially through either the cranial or the pharyngeal portions of the basiocciput, but does not extend all the way through to the other surface.…”

“…A complete CBM traverses entirely through the basioccipital bone, while an incomplete CBM can extend partially through either the cranial or the pharyngeal portions of the basiocciput, but does not extend all the way through to the other surface. Detailed illustrations of the six subtypes have been previously described in the literature and are beyond the scope of this report [2,4].…”

“…One, less likely, theory has been that the channels and foramina along the surface of the basiocciput are of vascular origin (emissary canals), while the other, more probable, theory attributes the presence of channels and pits to their being postnatal vestiges of the cephalic end of the notochordal canal (canalis chordae) [2,4]. The event causing this aberrant development occurs early in the fifth gestational week of embryonic life, when the notochord follows a ''sigmoid-like'' caudal-cranial curve that crosses the clivus approximately three times, initially perforating the occipital plate ventrally near the CBM, and then, when directly in contact with the endoderm of the pharynx, follows a rostral trajectory that penetrates the sphenoid plate near the dorsum sellae (Figure 2) [5,6].…”