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

Abstract

We report a patient with a cystic structure in the nasopharynx mimicking a Tornwaldt's cyst, which was felt to represent a different entity owing to the lack of the distinct features of a typical Tornwaldt's cyst. It was associated with a bony cleft in the basiocciput that was considered to be a canalis basilaris medianus (CBM), thought to represent an embryological vestige of the cephalic end of the notochord along its course within the basiocciput.

Figure 1

(a–d) Axial fat saturated T₂ weighted images. (a) Image through the cystic lesion (arrows) in the posterior midline nasopharnyx. (b) Slice more superiorly demonstrating the defect in the clivus. Arrows denote the partially hyperintense defect in the midline. (c) Inverted T₂ weighted image through the same level as (b) with better depiction of the canal within the bone. (d) More superior slice demonstrating the junction of the canal with the dural surface. (e and f) Thin slice CT images. (e) Axial and (f) sagittal images thin images from a dedicated skull base CT depicting the bony canal within the clivus. Arrow in (e) depict the broader anterior part of the canal which could be a so-called “foveola pharyngica”. Arrowheads in (e) point to the sclerotic posterior aspect of the defect. Arrows in (f) denote the broader anterior aspect; cranial communication could not be definitively demonstrated.

Figure 2

A different, normal patient with a sagittal view of the skull base showing a superimposed diagram of the craniocervical component of the expected embryonic notochordal trajectory in the adult (coloured line). The cephalic end of the notochord may be embedded in the bony sphenoid, while the segment in the basocciput level (arrows) may lie free in the nasopharyngeal wall.