Fossa navicularis in a pediatric patient: anatomical skull base variant with clinical implications

Radiologic Evaluation of the Fossa Navicularis on Dry Skull: A Comparative CBCT Study

Fossa navicularis (FN) is defined as bony depression that is not always present and is located anterior to the foramen magnum and pharyngeal tubercle on the inferior aspect of the basilar part of the occipital bone. It has been reported that FN can create an infection spread path from the pharynx to the intracranial structures. Therefore, the diagnosis of this variation is important. Although cone beam computed tomography (CBCT) diagnostic accuracy has mostly been verified in detection and quantification particularly on human skulls, there is no study comparing morphometric measurements between direct measurement on the skull and CBCT measurement. The main object of this study is to evaluate the presence of FN on dry bones and CBCT images of the same dry skull and to examine the morphometric and morphological features of this formation. Thirty-two random craniums that were made available for this study that did not have any fractures or deformities of the cranial base were examined. The sagittal diameter, transverse diameter, and depth of the FN was measured both directly on dry skulls and radiologically on CBCT images of dry skull. In addition, the shape of FN (SFN) was determined. FN was detected in 10 (31.25%) of 32 craniums examined with both modalities. It was determined that sagittal diameter of the FN, transverse diameter of the FN, depth of the FN, and the shape of FN did not show a statistically significant difference between the 2 measurements. Unlike the literature, FN was investigated on dry bones both directly and in CBCT images in this study. In contrast to previously thought the FN may be smaller according to this findings, and this small variation can be detected with CBCT images. According to this findings, it can be said that morphometric evaluations on CBCT are accurate and reliable, and CBCT is a safe method for clinical diagnosis and treatment.

Association of meningitis and clival canal defect: case illustration, management, and systematic review of the literature

OBJECTIVE

Improper embryological development of the clivus, a bony structure that comprises part of the skull base, can lead to a clival canal defect. Previously thought to be a benign condition, clival canals have been reported to be associated with meningitis and meningoceles. In this review, the authors sought to present an unpublished case of a patient with a clival canal defect associated with meningitis and to evaluate all other reported cases.

METHODS

In October 2020, a search of PubMed, Web of Science, and Scopus was conducted to identify all cases of clival canals reported from January 1, 1980, through October 31, 2020.

RESULTS

Including the case presented herein, 13 cases of clival canals, 11 in children (84.6%) and 2 in adults (15.4%), have been identified. Of the pediatric patients, 5 (45.5%) had an associated meningocele, and 8 (72.7%) had meningitis. Nine of the 13 patients (69.2%) had defects that were treated surgically, 5 (38.5%) by a transnasal approach and 4 (30.8%) by a transoral approach. Two patients (15.4%) were treated with drainage and antibiotics, 1 patient (7.7%) was treated solely with antibiotics, and 1 patient (7.7%) was not treated. In the literature review, 8 reports of clival canals were found to be associated with meningitis, further contributing to the notion that the clival canal may be an overlooked source of recurrent infection. In several of these cases, surgical repair of the lesion was curative, thus preventing continued episodes of meningitis.

CONCLUSIONS

When a patient has recurrent meningitis with no clear cause, taking a closer look at clival anatomy is recommended. In addition, if a clival canal defect has been identified, surgical repair should be considered a safe and effective primary treatment option.

Anomalies of the clivus of interest in dental practice: A systematic review

Purpose

The clivus is a region in the anterior section of the occipital bone that is commonly imaged on large-volume cone-beam computed tomography (CBCT). There have been several reports of incidental clivus variations and certain pathological entities that have been attributed to the variations. This study aimed to evaluate the effects of these variations within the scope of dentistry.

Materials and Methods

Medical databases (PubMed, Scopus, and Web of Science) were searched using a controlled vocabulary (clival anomalies, cone-beam CT, canalis basilaris medianus, fossa navicularis magna, clival variation). The search was limited to English language, humans, and studies published in the last 25 years. The articles were exported into RefWorks® and duplicates were removed. The remaining articles were screened and reviewed for supporting information on variations of the clivus on CBCT imaging.

Results

Canalis basilaris medianus and fossa navicularis magna were the most common anomalies noted. Many of these variations were asymptomatic, with most patients unaware of the anomaly. In certain cases, associated pathologies ranged from developmental (Tornwaldt cyst), to acquired (recurrent meningitis). While no distinct pathognomonic aspects were noted, there were unique patterns of radiographic diagnosis and treatment modalities. Most patients had a normal course of follow-up.

Conclusion

Interpretation of CBCT volumes is a skill every dentist must possess. When reviewing large-volume CBCT scans, the clinician should be able to distinguish pathology from normal anatomic variations within the skull base. The majority of clivus variations are asymptomatic and will remain undetected unless incidentally noted on radiographic examinations.

Radiologic evaluation of the fossa navicularis: incidence, morphometric features, and clinical implications

INTRODUCTION

The aim of this study was to determine the incidence and morphometric and morphological characteristics of fossa navicularis (FN) on cone beam computed tomography (CBCT) images of healthy adults MATERIALS AND METHODS: CBCT images of 900 individuals (450 males, 450 females, over the age of 18) admitted to Gaziantep University, Dentistry Faculty were retrospectively examined. The incidence and shape of FN were determined. Transverse diameter (TDFN), sagittal diameter (SDFN), depth in transverse section (DFNT), depth in sagittal section (DFNS), and the shortest distance between the deepest point of FN and intracranial cavity (FNI) were measured.

RESULTS

FN was detected in 122 (59 males and 63 females) of 900 (13.56%) CBCT images. No statistically significant difference was observed between gender and the incidence of FN. SDFN, TDFN, DFNS, DFNT and FNI were measured as 4.04 ± 1.71, 4.28 ± 1.34, 1.79 ± 0.68, 2.34 ± 0.85, and 6.76 ± 2.23 mm, respectively. Besides, FN was described as oval in 95 of 122 (77.87%) cases, while as round in 27 (22.23%) cases.

CONCLUSIONS

The incidence of FN is rare; however, it may be responsible for serious consequences by causing infections from the nasopharynx to the intracranial cavity. As far as we know, the distance between the deepest point of FN and the intracranial cavity was measured for the first time in the literature with this study.

Anatomical variations of clivus: a descriptive anatomical study

PURPOSE

The clivus is a part of the sphenoid bone. It may show some anatomical variations such as fossa navicularis magna (FNM), canalis basilaris medianus (CBM) and craniopharyngeal canal (CPC). These variations have been associated with conditions like meningitis and tumors of skull base. Inadequate information about these structures may pose a risk of inaccurate diagnosis resulting in unwarranted interventional procedures. Hence, the knowledge about the prevalence of these variations is important. Thus, the objective of this study was to determine the prevalence of fossa navicularis magna, craniopharyngeal canal and canalis basilaris medianus and its types utilizing cone-beam computed tomography (CBCT) images.

METHODS

Retrospectively, a total of 350 CBCT scans were evaluated for the presence of FNM, CBM, its types and CPC. The analysis was done by two observers independently. Cohen's kappa statistics was used to determine the interobserver agreement.

RESULTS

FNM was noted in 19.4% cases, CBM in 9.7% cases, whereas CPC was not identified in any case. Type 5 was the most common type of CBM. There was no significant difference (p > 0.05) between genders and age groups for the prevalence and a highly significant (p < 0.01) substantial agreement between observers for the prevalence of FNM and highly significant (p < 0.01) moderate agreement for the prevalence of CBM and its types was obtained.

CONCLUSION

FNM, CBM, CPC, albeit rare anatomical variations of clivus, knowledge of these structures is important for radiologists, anatomists and surgeons to avoid misdiagnosis and provide awareness to the individual of a higher possibility of meningitis or tumors of the skull base.

Evaluation of morphometric features of fossa navicularis using cone-beam computed tomography in a Turkish subpopulation

Purpose

Fossa navicularis is a bone defect in the clivus. Familiarity with this anatomical variant is important because it is close to vital anatomical structures in the base of the skull. The aim of this study was to determine the prevalence and morphometric properties of fossa navicularis within the clivus in a Turkish subpopulation using cone-beam computed tomography (CBCT).

Materials and Methods

A total of 168 CBCT scans (female: 96, male: 71) were evaluated. High-quality CBCT images of patients without a syndromic condition or a history of neurological disease or surgery were included in the study. The prevalence, depth, length, and width of the fossa navicularis were performed.

Results

The prevalence of fossa navicularis was 27.5% (n=46 patients). Sex was not associated with the depth, length, or width of the fossa navicularis (P>0.05). A significant positive correlation was found between age and length of the fossa navicularis (P>0.05).

Conclusion

Fossa navicularis was found to be rare (27.5%). Anatomical variants of the skull base can also be clearly identified on CBCT images. The results of this study may be useful to radiologists, anatomists, and surgeons interested in the skull base.