Fossa navicularis: Anatomic variation at the skull base

Abstract

The fossa navicularis is a relatively rare anatomic variation of the skull base. Awareness of its existence will avoid misinterpretations of radiological images and unnecessary investigations. This study describes the appearance of the fossa navicularis, and investigates its incidence and whether it is related to pathology at the basiocciput. We studied 492 dry human skulls and 525 computer tomography (CT) images of patients. Dry skulls showing a fossa navicularis were investigated by CT scan, whereas patients identified as having a fossa navicularis were further examined with magnetic resonance imaging (MRI). To document the position of the fossa more precisely, measurements were made between the fossa navicularis and certain anatomic landmarks such as the foramen ovale, the pharyngeal tubercle, the posterior border of the vomer, the foramen lacerum, the carotid canal, and the occipital condyle. Upon examination, 26 of 492 skulls (5.3%) were found to have a fossa navicularis. Twelve were <2 mm in depth and the other 14 had a depth of >/=2 mm. Of the 525 patients, 16 (3.0%) were identified as having a fossa navicularis in CT images. Evaluation of MRIs showed no soft tissue lesions in any of these patients. Comprehensive anatomic details of the fossa navicularis have not been reported in the literature. The results of this study may be useful to radiologists, anatomists, and surgeons interested in the skull base.

The First Histological Analysis of the Tissues Lining the Fossa Navicularis: Insights to its Etiology

“…The existence of the vascular matrix might support the former theory of the embryology but does not support a notochordal etiology for the development of the FN. In addition, several MRI studies have described the FN as being filled with lymphoid tissue of the nasopharyngeal tonsils but have made these comments without histology [2-4]. Our study showed soft tissue in the fossa but no lymphoid tissue was found within it.…”

“…Of them all, our literature review found that the FN has been used most frequently with some making distinctions between the FN and the median basal canal [2, 4-5]. According to Currarino [5], the FN is a rare anatomic variant of the basiocciput and is a subtype of the canalis basilaris medianus (CBM) [6].…”

“…The etiology of these depressions has only been speculated until date. For example, some authors have posited that this fossa could be filled with nasopharyngeal tonsillar tissue [2-4]. However, to our knowledge, none of the previous studies has performed histological observation of the contents of the FN.…”

Prevalence of fossa navicularis among cleft palate patients detected by cone beam computed tomography

“…Prevalence of fossa navicularis was reported by several researchers, ranging between 0.9-5.3% on DISCUSSION This is the first study that demonstrated the prevalence of fossa navicularis among cleft palate patients using a CBCT device. Prevalence of fossa navicularis was reported by several researchers, ranging between 0.9-5.3% on dried skulls [4][5][6][7] , 3% on CT images 4 and 6.6% on CBCT images3. The percentage of fossa navicularis identified in this study (28.8%), was found to be higher than the percentage reported in previous studies performed on dry skulls, CT or CBCT images of the noncleft patients.…”

Morphological variations in the basioccipital region of the South Indian skull

“…28 But in present case the depth was much less compared to previous study. According to Cankal 7 and his associates differential diagnosis of fossa navicularis includes Rathke's pouch cyst, adenoid retention cyst, adenoid hypertrophy, Tornwaldt's cyst, mucocele of sphenoidal sinus, dermoidteratoma of posterior nasopharyngeal wall.…”