The posterior groove as a landmark for location of the palatovaginal canal in axial computed tomography

The importance of the palatine bone for endoscopic endonasal skull base surgery

Endoscopic endonasal skull base surgery is increasingly prevalent, with its scope expanding from pathogens in the midline region to those in the paramedian region. Maximizing anterior sphenoidectomy is important for the median approach, and lateralizing the pterygopalatine fossa is crucial for the paramedian approach. Maximizing the surgical corridor in the nasal cavity and minimizing damage to neurovascular structures are vital for establishing a surgical field with minimal bleeding, ensuring safe, precise, and gentle procedures. However, the relationship between the maxillofacial and skull base bones in endoscopic endonasal skull base surgery is difficult to understand because these bones are intricately articulated, making it challenging to visualize each bone's outline. Understanding important bones and their related neurovascular structures is essential for all skull base surgeons to maximize the surgical corridor and minimize iatrogenic injury to neurovascular structures. This study aimed to elucidate the role of the palatine bone from a microsurgical anatomical perspective. Three dry skulls were used to demonstrate the structure of the palatine bone and its relationship with surrounding bones. A formalin-perfused cadaveric head was dissected to show the related neurovascular structures. The arteries and veins of the cadaveric heads were injected with red- and blue-colored silicon. Dissection was performed using a surgical microscope and endoscope. In addition, the utilization of the palatine bone as a landmark to identify neurovascular structures, which aids in creating a wider surgical field with less bleeding, was shown in two representative cases. The palatine bone consists of unique complex structures, including the sphenoidal process, ethmoidal crest, pterygopalatine canal, and sphenopalatine notch, which are closely related to the sphenopalatine artery, maxillary nerve, and its branches. The ethmoidal crest of the palatine bone is a well-known structure that is useful for identifying the sphenopalatine foramen, controlling the sphenopalatine artery and nerve, and safely opening the pterygopalatine fossa. The sphenoidal process of the palatine bone is a valuable landmark for identifying the palatovaginal artery, which is a landmark used to safely and efficiently expose the vidian canal. The sphenoidal process is easily cracked with an osteotome and removed to expose the palatovaginal artery, which runs along the pharyngeal groove, just medial to the vidian canal. By opening the pterygopalatine canal (also known as the greater palatine canal), further lateralization of the periosteum-covered pterygopalatine fossa contents can be achieved. Overall, the sphenoidal process and ethmoidal crest can be used as important landmarks to maximize the surgical corridor and minimize unnecessary injury to neurovascular structures.

Incidence of anomalous canals in the base of the skull: a retrospective radio-anatomical study using cone-beam computed tomography

PURPOSE

Several skull-base foramina including foramen meningo-orbitale, craniopharyngeal canals, canaliculus innominatus, foramen vesalius, palatovaginal canals, and canalis basalis medianus are visible on cone-beam computed tomographs. A good understanding of the anatomical variants of these foramina is important to accurately diagnose fractures, understand the paths that infections may take, and identify associated anomalies. We used cone-beam computed tomography to measure the incidences of skull-base foramen variants in a normal population.

METHODS

A total of 350 subjects (200 females, 150 males, 6-30 years of age) were included. The prevalences of foramen meningo-orbitale, craniopharyngeal canals, canaliculus innominatus, foramina vesalius, palatovaginal canals, and canalis basalis medianus were evaluated by age and gender.

RESULTS

Subject age ranged from 6 to 30 years (mean age ± SD = 15.1 ± 4.08). Foramen meningo-orbitale, craniopharyngeal canals, canaliculus innominatus, foramen vesalius, palatovaginal canal, and canalis basalis medianus were observed in 51 (14.6%), 19 (5.4%), 60 (17.1%), 145 (41.1%), 34 (9.7%), and 15 (4.3%) patients, respectively.

CONCLUSIONS

Skull-base foramina are important clinically and radiologically. Imaging of such variants via cone-beam computed tomography is valuable for both physicians and patients. Few studies of skull-base foramina have used cone-beam computed tomography. Additional research is required for a fuller understanding of this phenomenon.

Visualisation of the vomerovaginal canal during endonasal transpterygoid approaches and CT imaging diagnosis

The vomerovaginal canal (VVC) and palatovaginal canal (PVC) are two canals that open forward to the posterior wall of the pterygopalatine fossa (PPF). Although the anatomy and computed tomography (CT) appearances of the PVC have been well studied, the VVC has been rarely reported, especially in endoscopic examinations. Some studies have even failed to distinguish the PVC from the VVC on CT images. The purpose of this study was to demonstrate the anatomy of the VVC on endoscopy and reveal its differences from the PVC, and to analyse the relative positions of the VVC, PVC, and pterygoid canal on CT images. Ten dry skull bases were studied to observe the structures involved in the formation of the VVC. Dissection of four cadaveric heads was performed to demonstrate the anatomy of the VVC on endoscopy. Coronal CT image analysis in 70 patients was conducted to evaluate the distances and relative positions between the VVC, PVC, and pterygoid canal. The PVC and VVC were also compared on axial CT images. The osteological study showed the top wall of the VVC was the antero-inferior wall of the sphenoid sinus. The VVC may be a helpful landmark in endoscopic endonasal transpterygoid approaches. Steps and discrimination in the dissections of the VVC and PVC were described. The interval between the PVC and VVC could be observed on both coronal and axial CT images. The coronal CT images of patients showed differences in the positions and distances among the three canals at both the anterior and posterior apertures of the PVC. The VVC can be easily mistaken for the PVC if its existence is not suspected. The anatomical morphologies and trajectories of the VVC and PVC differed on both nasal endoscopy and CT. The existence of the VVC should be considered during surgery and CT diagnosis within this area.

Visualization of the vidian canal and nerve using magnetic resonance imaging

BACKGROUND AND PURPOSE

Few studies have investigated the vidian nerve (VN) and vidian canal (VC) with the use of magnetic resonance imaging (MRI). The present study aimed to characterize the VC and VN using MRI.

MATERIALS AND METHODS

A total of 91 patients underwent thin-sliced, contrast MRI. The course of the VC and VN and the relationships with relevant structures were analyzed.

RESULTS

The VC was identified in 95% of axial images on the right side and in 93% on the left. The course of the VC was delineated in 99% of serial coronal images on both sides. The VN location in the VC was highly variable. The course of the VC and transmitting VN was delineated in 95% of sagittal images on the right side and in 91% on the left. The mean length of the VC was 19.8 mm on the right side and 19.3 mm on the left. Topographical relationships between the anterior genu of the petrous internal carotid artery and the posterior end of the vidian canal could be classified into three types. Of these, the type terminating at the level of the petrous carotid was the most predominant, comprising 76% of 182 sides. The course of the VC and transmitting VN could be classified into four types. The straight type was the most predominant and was found in 41%.

CONCLUSIONS

The VC and transmitting VN are structures with variable morphologies. Contrast MRI is useful for delineating the VC and VN.