the cbct data of a 11-year - old female was referred to evaluate radiolucency in the apical area of the maxillary left lateral incisor . the patient presented with no clinical symptoms and had a non - contributory medical history . the cbct scan was obtained with i - cat unit ( imaging science , hatfield , pa , usa ) . the digital imaging and communications in medicine ( dicom ) deidentified data was sent through a health insurance portability and accountability act - compliant secure email ( brightsquid , ross technology centre , calgary , alberta , canada ) and the data was evaluated using invivo5.4.3 ( anatomage , san jose , ca , usa ) . all data was evaluated by two board - certified oral and maxillofacial radiologists ( saz , sar ) . it was observed that the sagittal view was optimal for the visualization of this entity because of its extension in the anterioposterior direction across the clivus . radiographically cbm can be described as a well - defined , corticated and channel - like hypodense radiolucency extending from the pharyngeal aspect of the basiocciput to the intracranial aspect of the clivus . 1 ) . a 63-year - old female patient with a significant medical history of arthritis , thyroid disease , sinusitis , and gastrointestinal disease was referred for a cbct scan . , atlanta , ga , usa ) , and the patient was referred for the evaluation of a proposed implant site in the maxillary region . the data was analyzed using multiplanar reformatted slices by a board - certified oral and maxillofacial radiologist ( mm ) . the volumetric data set revealed an unusual finding on the basiocciput of the clivus . in the sagittal view the intracranial part of the clivus showed discontinuity , the radiographic presentation of this osseous defect presentation can be described as a well - corticated , hypodense channel extending in the superior - inferior direction along the intracranial aspect of the clivus ( fig . 2 ) . on initial inspection it appeared to be a fracture of the clivus . however , further close inspection revealed no other signs of osteolytic destruction on the posterior aspect of the clivus ( intracranial surface ) . based on the volumetric appearance of the defect , a radiographic impression of cbm was made . the cbct data of a 11-year - old female was referred to evaluate radiolucency in the apical area of the maxillary left lateral incisor . the patient presented with no clinical symptoms and had a non - contributory medical history . the cbct scan was obtained with i - cat unit ( imaging science , hatfield , pa , usa ) . the digital imaging and communications in medicine ( dicom ) deidentified data was sent through a health insurance portability and accountability act - compliant secure email ( brightsquid , ross technology centre , calgary , alberta , canada ) and the data was evaluated using invivo5.4.3 ( anatomage , san jose , ca , usa ) . all data was evaluated by two board - certified oral and maxillofacial radiologists ( saz , sar ) . it was observed that the sagittal view was optimal for the visualization of this entity because of its extension in the anterioposterior direction across the clivus . radiographically cbm can be described as a well - defined , corticated and channel - like hypodense radiolucency extending from the pharyngeal aspect of the basiocciput to the intracranial aspect of the clivus . a 63-year - old female patient with a significant medical history of arthritis , thyroid disease , sinusitis , and gastrointestinal disease was referred for a cbct scan . atlanta , ga , usa ) , and the patient was referred for the evaluation of a proposed implant site in the maxillary region . the data was analyzed using multiplanar reformatted slices by a board - certified oral and maxillofacial radiologist ( mm ) . the volumetric data set revealed an unusual finding on the basiocciput of the clivus . in the sagittal view the intracranial part of the clivus showed discontinuity , the radiographic presentation of this osseous defect presentation can be described as a well - corticated , hypodense channel extending in the superior - inferior direction along the intracranial aspect of the clivus ( fig . 2 ) . on initial inspection it appeared to be a fracture of the clivus . however , further close inspection revealed no other signs of osteolytic destruction on the posterior aspect of the clivus ( intracranial surface ) . based on the volumetric appearance of the defect , the term cbm is used to describe transclival defect of the basicocciput of the clivus . cbm presents itself in various configurations such as keyhole defect , transverse or longitudinally fissures in the clivus.12 radiological features of cbm can be described as a well - defined , corticated , osseous transclival defect located in the basiocciput of the clivus . in the axial view it is located in close approximation to the anterior rim of the foramen magnum.10 cbm 's reported prevalence in the literature is is 2%-3% for adults and 3 ) were described in the literature : three complete varieties ( superior , inferior , and bifurcated ) and three incomplete varieties ( a thin , long channel ; and either a superior recess ; or an inferior recess).910 the complete type of cbm is characterized by the presence of a channel or tract like hypodense region extending either anterio - posteriorly or superior - inferior direction occasionally , connecting the intracranial and pharyngeal portions of the clivus . incomplete type will traverse partially within the clivus and they fail to communicate with pharyngeal portion or intracranial of the portion of the clivus . cbm in general is considered an anatomical variant without any clinical significance.89 however , few studies indicate that they could serve as potential pathways for the progression of the disease such as meningitis.13 hemphill et al.11 and martinez et al.12 reported a transclival bony defect that was associated with a meningocele and caused recurrent meningitis . however , authors argued that a mere coexistence of cbm and meningitis may not have caused detrimental effects such as optic neuropathy and the episode of sterile meningitis as noted in their case.9 lohman et al.13 reported a cbm in association with a tornwaldt cyst for the first time in the literature . literature is providing conflicting reports about cbm 's association with other pathological entities such as meningitis , tornwaldt 's cyst and its detrimental effects as noted in the above description . first case described was incomplete type and second case was complete type of cbm , both cases were assessed using cbct . in both the cases , the occurrence of cbm was not associated with meningitis or other problems . our experience , as well as the literature as a whole , emphasizes the need for thorough analysis of skulls regardless of whether defects are detected or not when diagnostic tools such as cbct , ct , and mri are readily available.25 we recommend that all data should be interpreted by a board - certified oral and maxillofacial radiologist to prevent misdiagnoses and to avoid potential complications.7
the aim of this report is to present two cases of canalis basilaris medianus as identified on cone - beam computed tomography ( cbct ) in the base of the skull . 
 the cbct data sets were sent for radiographic consultation . in both cases , multi - planar views revealed an osseous defect in the base of the skull in the clivus region , the sagittal view showed a unilateral , well - defined , non - corticated , track - like low - attenuation osseous defect in the clivus . 
 the appearance of the defect was highly reminiscent of a fracture of the clivus . 
 the borders of osseous defect were smooth , and no other radiographic signs suggestive of osteolytic destructive processes were noted . 
 based on the overall radiographic examination , a radiographic impression of canalis basilaris medianus was made . 
 canalis basilaris medianus is a rare anatomical variant and is generally observed on the clivus . due to its potential association with meningitis , it should be recognized and reported to avoid potential complications .