Canalis Basilaris Medianus Research Articles

Canalis basilaris medianus: An anatomical study

BackgroundThe clivus, a key skull base structure for neurosurgeons due to its proximity to brainstem areas, is formed by the fusion of two bones. A rare variation, the canalis basilaris medianus (CBM) or clival canal, can exist within the occipital bone. The clivus has a rich venous network, and the CBM's presence might be linked to veins or embryonic structures. Understanding the CBM is valuable for interpreting clival fractures and during neurosurgery. This study aimed to determine the frequency and morphometric parameters of the CBM. Material and methodsFifty-nine dry adult skulls were selected for the investigation. Morphometric measures included establishing the diameters of the internal and external foramina of the CBM, the length of the canal, and its distance from the foramen magnum (FM), jugular tubercles, and lateral margins of the basilar part of the occipital bone. ResultsOut of the 59 skulls investigated, only a single specimen contained the CBM. Thus, the frequency of canal presence in our sample was 0.59 %. The internal foramen of the CBM was located on the internal surface of the clivus, 4.03 mm anteriorly to the FM with a diameter of 2.84 mm. Further, the canal passed through the clivus and had its external foramen on the external surface of the clivus at 0.11 mm above the pharyngeal tubercle and its distance from the FM was 9.19 mm. The length of the CBM was established at 8.16 mm. ConclusionThe CBM is a rare variation of the basilar part of the occipital bone. Therefore, the possibility of the existence of this variation should be considered when analyzing CT and MRI images to avoid misinterpretation of their results and during surgical interventions in this area.

Canalis Basilaris Medianus as an Anatomical Variation in the Basilar Part of the Occipital Bone: A Descriptive Cone Beam Computed Tomographic Study

Abstract Objectives: Canalis basilaris medianus (CBM) is a unique anatomical variation located in the basal occipital region of the skull, rarely encountered in head and neck radiographic imaging. The aim of the present study was to evaluate the prevalence and types of CBM using Cone Beam Computed Tomography (CBCT) scans. Materials and Methods: CBCT (Full FOV) images of 200 patients aged between 10 to 70 years were selected for the current retrospective study following the inclusion and exclusion criteria. The image sections from the scan data were scrutinized for the presence of CBM, in addition to its classification based on the type of morphology. The presence and types of CBM were recorded based on the age and gender. The chi-square test was used to analyze the presence and types of CBM with regard to gender and age group. Results: The overall prevalence of CBM was estimated as 9.5%. CBM was present in 13% of males and 3% of females (p = 0.021). Considering the types of CBM, the superior recess type was predominantly observed followed by the inferior recess, superior and inferior type. However, there was no significant gender-based differences noted among the types of CBM (p > 0.05). Also, there was no statistically significant difference noted in the prevalence of CBM in different age groups (p > 0.05). Conclusion: It is necessary for maxillofacial radiologists to have a solid understanding of both normal and variant skull-base anatomy to facilitate recognition of variants such as CBM in order to recognize the associated anomalies. To our knowledge, this was the first study done which assesses the gender-based differences among the various types of CBM.

Investigation of the prevalence and main features of skull-base anomalies and characteristics of the sphenoid sinus using cone-beam computed tomography.

ObjectivesThis study aimed to define the prevalence and characteristics of skull base anomalies and the features of sphenoid sinus pneumatization (SSP).Materials and MethodsFive hundred cone-beam computed tomography scans were evaluated retrospectively for the presence of fossa navicularis magna (FNM), canalis basilaris medianus (CBM), sphenoid emissary foramen (SEF), and/or Onodi cells (OC). Patterns of the SSP and sphenoid sinus mucosa dimensions (SSMD) were also recorded.ResultsThe prevalence of FNM, CBM, SEF, and OC was 26.0%, 22.4%, 47.4%, and 18.4%, respectively. Two hundred sixty-two (52.4%) sellar-type SSP were defined, followed by post-sellar 191 (38.2%), pre-sellar 31 (6.2%), and conchal 16 (3.2%) types. The frequency of SSMD less than 1 mm, 1-3 mm, and greater than 3 mm was 40.6%, 38.4%, and 21.0%, respectively. An SEF was detected more frequently in females, while SSMD greater than 3 mm was more frequent in males. An FNM was more prevalent in the 18-29 and 30-39 age groups and SEF was significantly less frequent in patients over 60 years of age compared to other age groups. A sinus mucosa larger than 3 mm was more common in the younger than 18 year group. The frequency of post-sellar-type pneumatization was lower in patients younger than 18 years.ConclusionSkull-base anomalies are common and may be detected incidentally during imaging procedures. The sphenoid sinus, its variations, and pneumatization patterns should also be taken into consideration in imaging procedures performed for various purposes.

Cone-Beam Computed Tomography a Dynamic Tool for Assessment of Canalis Basilaris Medianus a Skull Anomaly – A Retrospective Study

Introduction: Canalis basilaris medianus (CBM) is an anomaly of basiocciput in the clivus at the skull's base, demonstrating six different morphological varieties. CBM can be associated with recurrent meningitis and various other cranial pathologies. It can be seen on maxillary cone-beam computed tomography (CBCT) scan with comparatively less radiation dose than computed tomography (CT). Aim: The aim of this study is to determine a prevalence of CBM on CBCT. Objectives: The objectives of this study are: 1. To identify CBM on CBCT 2. To classify CBM according to their morphological types using CBCT. Methods and Material: This study included 300 maxillary CBCT scans retrieved from archival records from the CBCT diagnostic center, Department of Oral Medicine and Radiology, and the existence of CBM were examined. Scans of both genders with all age groups were selected. The existence of CBM was examined and classified based on its morphological type. Results: Chi-square test was used to carry out the descriptive statistics. The presence of CBM was found in 16 scans with a prevalence rate of 5.33%. Out of 16 scans, 10 (62.5%) were females, and 6 (37.5%) were males. Among them, 13 (81.25%) scans were superior recess variety, and 3 (18.75%) were inferior recess variety; other morphological types were absent. Conclusion: Although the prevalence rate of this anomaly is low, it is clinically significant as it may cause the spread of nasopharyngeal infections to the skull base. The present study revealed that a CBCT scan of the maxillary arch could provide a clear delineation of CBM with comparatively less radiation dose than CT. To the best of our knowledge, the recorded values of the prevalence rate of CBM available in current literature are lower compared to this first-ever study carried out in India.

Morphological Measurement and Anatomical Variations of the Clivus Using Computed Tomography.

Objectives The aim of this study was to evaluate the clivus morphology, including fossa navicularis magna (FNM), canalis basilaris medianus (CBM), and craniopharyngeal canal (CC), on computed tomography (CT) images. Design This is a retrospective study. Setting Faculty of Dentistry, Department of Dentomaxillofacial Radiology. Participants The CT images of 500 patients (253 males; 247 females) were evaluated. Main Outcome Measures The prevalence of FNM, CBM, and CPC; the length, width, and depth of FNM; and CBM types were recorded. Also, a morphological analysis of the clivus (length of the clivus, angle between the clivus and the posterior margin of the foramen magnum, angle between the clivus and the dens axis, and anteroposterior diameter of the foramen magnum) was performed. Results FNM was identified in 5.4%, CBM in 4%, and CC in 0.8% of the study group. Type 5 CBM was not found. Type 6 was the most common CBM type. There was no significant correlation between the age and gender of patients with FNM. There were significant differences between the clivus length, the angle between the clivus and the dens axis, the anteroposterior diameter of the foramen magnum, and gender. Also, there was a significant difference between the angle between the clivus and the foramen magnum and age. Conclusions The anatomical variations of the clivus are rare and important for the oral and maxillofacial radiologist to make the differential diagnosis. These anatomical variations should not be confused with pathologic formations. The morphological measurements and anatomical variations of the clivus can be evaluated in detail on CT images.

Anatomical variations of clivus: a descriptive anatomical study.

The clivus is apart 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 andcanalis basilaris medianus and its types utilizing cone-beam computed tomography (CBCT) images. 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. 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. 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.

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

PurposeThe 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 MethodsMedical 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.ResultsCanalis 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.ConclusionInterpretation 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.

JOURNEY OF THE NOTOCHORD: LINKING EMBRYOLOGY TO RADIOLOGIC INTERPRETATION OF THE CRANIOCERVICAL JUNCTION

<h3>Background</h3> The notochord is a mesoderm-derived cylindrical midline structure and a defining feature found in all chordates. In vertebrates, the notochordal process represents the initial embryologic axial skeleton and plays important structural and signaling roles in the development of the vertebral column, nervous system, and skull base. Besides persisting postnatally as the nucleus pulposus of the intervertebral disks, the remaining notochord typically regresses during fetal development after completion of its principal tasks. However, remnants of the notochord can persist along its developmental path within the craniocervical region. These remnants present as a spectrum of entities, ranging from anatomic variants, benign tumors, and malignant neoplasms of notochordal origin. Radiologists who interpret imaging in the area along the embryologic path of the notochord should be knowledgeable about its development and be able to recognize its wide array of potential pathologies. <h3>Discussion</h3> This presentation will review notochord embryology and the anatomic and pathologic relevance of notochordal remnants and demonstrate the vast range of imaging features and behavioral properties of these postnatal remnants in the area of the posterior cranial base and cervical spine. We present 3 cases of inferior median clival canal, a notochordal anatomic variant typically discovered as an incidental finding. Also known as <i>canalis basilaris medianus</i>, this notochord remnant manifests as a narrow, well-defined corticated canal passing through the sagittal plane of the clivus. Depending on its course and extent, 2 groups with 6 subtypes have been described. We also present imaging features of pathologic abnormalities, including Tornwaldt cyst, benign remnant ecchordosis physaliphora, and chordoma, a notochord malignancy. Awareness of the full spectrum of pathologic consequences of persistent notochord tissue, recognition of their imaging features, and directing appropriate referral add to the value provided by an oral and maxillofacial radiologist.

Know Your Notochord: A Pictorial Review of Notochord Remnants

Notochord formation begins between the third and fourth weeks of embryonic development. As the axial skeleton develops, the notochord regresses and eventually contributes to the formation of the nucleus pulposus of the intervertebral disks. Notochord regression can be variable, especially at the 2 poles of the skeleton, which results in the persistence of ectopic notochordal remnants. These remnants include benign entities (eg, ecchordosis physaliphora, benign notochordal cell tumor, Tornwaldt cyst, canalis basilaris medianus, fossa navicularis) or malignant lesions (eg, chordoma). We present a review of these lesions, their clinical presentations, and their typical radiographic appearances. Notochord remnants may have overlapping features in terms of their location and appearance; however, differentiation is crucial because the proper treatment and management may differ drastically. Familiarity with notochord development aids in understanding the characteristic locations of notochordal remnants. Noting the unique imaging findings of notochordal remnants can often help narrow the differential diagnoses.Learning Objective: To describe notochord development, normal regression during fetal life, and notochord remnants that give rise to anatomic variants, including benign and malignant lesions.

Prevalence of anatomical variants in the clivus: fossa navicularis magna, canalis basilaris medianus, and craniopharyngeal canal.

This study determined the prevalence of fossa navicularis magna (FNM), canalis basilaris medianus (CBM), and craniopharyngeal canal (CPC), the size of FNMs, and types of CBM using 3D computed tomography (CT) images. A total of 1059 3D images [649 cone beam computed tomography (CBCT) and 410 CT] were evaluated in this study. The prevalence of FNM, CBM, and CPC, length, width, and depth of FNM, and type of CBM were assessed. Overall, FNM was identified in 7.6%, CPC in 0.3%, and CBM in 2.5% of the study group. Type 2 (0.1%) and Type 6 (0.1%) are the least common CBM types. There was no significant difference between genders for depth and width measurements (p > 0.05), however, the length of FNM was significantly higher in males than females in CBCT images (p = 0.02). FNM, CBM, and CPC are rare anatomical variants of clivus. However, they can facilitate spread of infection to the skull base or vice-versa. These types of anatomical variations should be known by radiologists to avoid unnecessary diagnosis and treatment procedures and to distinguish anatomic variations from pathological conditions.

Prevalence and morphometric features of fossa navicularis on cone beam computed tomography in Turkish population

The objective of this study is to determine the prevalence and morphometric features of fossa navicularis, a close radiographic anatomic variation of canalis basilaris medianus of the basiocciput, in a Turkish population, using cone beam computed tomography (CBCT). The study group consisted of 723 patients (female: 420, male: 303) having CBCT scans. The patients had no syndromes, history of neurological diseases or surgery in the area of interest. On the images that revealed a fossa navicularis, the depth, length, and width measurements were performed, and were compared to the age and gender of the patients. The shape and number of fossa navicularis were also recorded. Fossa navicularis was identified in 48 (6.6%) patients. Among these patients, 19 were female (4.5% of all female patients), whereas 29 were male (9.6% of all male patients), and their age ranged between 10 and 68 years (mean age: 34.0 ± 18.7). No significant difference was found between genders and age groups in terms of depth, length, and width measurements (p > 0.05). In 39 (5.4%) patients, fossa navicularis presented oval in shape. Even though the prevalence of fossa navicularis was found to be higher than previously reported, it still seems to be rare. Anatomical structure of the fossa navicularis can be studied effectively on CBCT images.

Incidental findings on cone beam computed tomographic images: a Pandora's box?

Incidental findings on cone beam computed tomographic images: a Pandora's box?

Multi–Detector-Row Computed Tomography Imaging of Variant Skull Base Foramina

Several inconstant skull base foramina can be observed on multi-detector-row computed tomographic studies. These include the meningo-orbital foramen, foramen of Vesalius, canaliculus innominatus, palatovaginal canal, persistent craniopharyngeal canal, transsphenoidal canal, canalis basilaris medianus, and fossa navicularis. Although many of these foramina are simply incidental findings, there may be associated anomalies and important clinical implications. The multi-detector-row computed tomographic features of variant skull base foramina are depicted and discussed in this article.

Pharyngeal enterogenous cyst associated with canalis basilaris medianus in a newborn

We report the CT and MR characteristics of a newborn with a rare, complex malformation characterised by a large rhinopharyngeal and oropharyngeal enterogenous cyst, associated with an osseous defect of the basiocciput, called canalis basilaris medianus (CBM). A partial herniation of the bulb was demonstrated through the bony defect on the midline. The enterogenous cyst occupied the rhinopharynx and oropharynx, narrowing the pharyngeal lumen and making it difficult for the introduction of an orotracheal tube.

The clinical importance of basioccipital developmental defects

Dear Editor: We read with great interest the article by Tubbs et al. entitled “The human calvaria: a review of embryology, anatomy, pathology, and molecular development,” published in Child’s Nervous System (2012;28(1):23–31). In their paper, the authors provide an extensive review about the development, pathology, and molecular formation of the human calvaria. Although in their approach to the neurocranium the authors focus their attention on the human calvaria (also known as membranous cranium), this article also provides interesting information about the development of the cranial base (or chondrocranium). As highlighted by the authors, the embryological processes responsible for the formation of the final architecture of the skull starts with the chondrification of the mesenchyme of the spheno-occipital region during the seventh fetal week, further extending to the facial bones and lately spreading and expanding the neurocranial cavity to accommodate the enlarging forebrain. Although the presented knowledge about the embryological development of the calvaria seems to have clear clinical applications due to the importance of the several types of craniosynostosis in the neurosurgical pediatric practice, it is important to emphasize that the knowledge about the development of the skull base should not be regarded as secondary. In fact, although most of the skull base developmental defects usually represent incidental findings on imaging exams, they may constitute an unrecognized cause of recurrent meningitis, especially after paranasal sinus infections. With special clinical importance is the so-called “Canalis Basilaris Medianus” (CBM), a special type of basiocipital developmental defect. Although the reported incidence of such anomaly in old CT scans series was around 3.8% [3], a most recent report found a much higher incidence (around 20%) [6]. In early embryological development, the four sclerotomes of the first four somites (called hypoglossal somites) are incorporated into the skull base. At this location, these elements fuse and establish the basioccipital plate, which surrounds the notochord. The spinal and the pre-chordal part are responsible for the formation of the chondrocranium, also called the primordial cranium. The embryology and development of the sphenoid bone are complex and involve up to 15 separate enchondral and intramembranous ossification centers [5]. According to this mosaic-like formation, several interosseous sutures are established and may, in some cases, persist towards adulthood [11]. In fact, the absence of complete fusion of these embryological ossification centers may lead to the persistence of seven other types of anterior skull base foramina or pseudoforamina besides the “Canalis Basilaris Medianus’ [6]. Two theories have been proposed in the literature to explain the development of the CBM. The most accepted one suggests that the defect would be an osseous remnant of a basivertebral vein present only in the embryological phase of development [4, 8]. Another theory relates the origin of CBMs to notochordal development [2]. It is known that around the fifth week, the notochord becomes enclosed by the bodies of the upper cervical vertebrae. During regular embryological development T. A. Mattei (*) Neurosurgery Department, University of Illinois at Peoria, 828 NE Glen Oak Avenue, Apt. 302, Peoria, IL 61603-3285, USA e-mail: tobiasmattei@yahoo.com

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

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.

Spontaneous Transclival Cerebrospinal Fluid Fistulae

Introduction: A transclival spontaneous fistula is a rare event. It usually becomes symptomatic and is detected by means of either CSF rhinorrhea or intracranial complications such as meningitis. Different skull base variants of normality have been described in anatomic and radiological literature. Of special interest to surgeons is the possibility that some of such bone variants occur in the embryological formation of the anterior skull base, resulting in a local bone defect or persistence of a vascular canal in the clivus that might become symptomatic after a precipitating factor such as skull base approaches. Case Report: We present a case of a CSF fistula due to a clival bone defect manifesting after transsphenoidal surgery for a pituitary microadenoma. We did not consider it a postsurgical complication because no extended approach was employed and the clival bone was not drilled by surgical maneuvers. The case is illustrated with pre-, intra-, and postoperative images, and the pathophysiology of spontaneous transclival fistula, as well as its possible complications and management, is discussed with basis in current literature. Conclusion: The authors suggest that the patient harbored an embryological remnant, previously described as “canalis basilaris medianus,” which, after resection of clival mucosal layer, communicated the CSF space around the clival area with the retropharynx. The possibility of detecting such embryological remnants preoperatively and its consequences of alerting to the possibility of early postoperative fistulas make this report of value for skull base surgeons.

CT of Normal Variations of the Minute Central Skull Base Foramina

Purpose : To evaluate the CT appearance of normal variations in the minute central skull base foramina in in-fants and children. Materials and Methods : One hundred and fourteen children under the age of 17 years without skull base ab-normality underwent CT scanning. A high spatial frequency algorithm was used, and contiguous axial scanning parallel to the orbitomeatal line was performed from the foramen magnum to the orbital roof, with a 1-mm slice thickness. The presence or absence of eight foramina, pseudoforamina, or ossification centers including anterior presphenoidal foramen, posterior presphenoidal foramen, rostro-orbital pseudoforamen, intralateromedial postsphenoidal pseudoforamen, intrapostsphenoidal pseudoforamen, spheno-occipital pseudo-foramen, canalis basilaris medianus and intrasynchondral ossified bodies was analysed according to age. The presence of foramina or pseudoforamina was indicated if a ring-shaped structure was seen on two or more CT scans at the location anatomically predicted, and intrasynchondral ossified bodies were indicated if linear or dot-like structures with high attenuation accompanied spheno-occipital synchondrosis. Results : CT indicated that within a certain age range, various kinds of foramina, pseudoforamina, and ossifi-cation centers were frequent. The anterior presphenoidal foramen was most commonly seen in infants aged 1-12 months (16/17, 94 %); the posterior presphenoidal foramen in children less than 2 years old(27/37, 73 % ) ; the rostro-orbital pseudoforamen in children aged 2 -5 years (9/17, 53%); intrapostsphenoidal pseudoforamen in children 6 -12 years old(20/37, 54%) and spheno-occipital pseudoforamen and intrasynchondral ossified bodies in children aged 13 -16 years. The canalis basilaris medianus was identified in about 20 % of all subjects regardless of age. Conclusion : Development of the minute central skull base foramina varied greatly according to age. Knowledge of the CT appearances of such embryologic variants of the central skull base should not only help Provide an understanding of complex skull base anatomy but also identify abnormal skull base development.

The foveola pharyngea--demonstration in conventional tomography and computed tomography (author's transl)

The foveola pharyngea is a cavity on the underside of the clivus, located before the tuberculum pharyngeum and, as a lager pit it was detectable in approximately 1%, overall in approximately 4% of the personally examined x-rays (11/284) and computed tomograms (6/154) of the skull base. The canalis basilaris medianus inferior and canalis basilaris medianus bifurcatus almost always empties into one of the three forms of the foveola pharyngea (foveola pharyngea infundibuliformis posterior). The differential diagnosis to canalis basilaris medianus, canalis craniopharyngeus, suture sphenooccipitalis and bone destruction is discussed.