Ossification of the pterygoalar and pterygospinous ligaments: a computed tomography analysis of infratemporal fossa anatomical variants relevant to percutaneous trigeminal rhizotomy

A comprehensive morphometric analysis of pterygospinous and pterygoalar bars on computed tomography images

This study is aimed to determine the prevalence and morphometric characteristics of the pterygospinous (Ps) and pterygoalar (Pa) bars using computed tomography (CT) images on an extensive study sample of the Anatolian population. The CT images of 700 patients (350 males, 350 females) were analyzed for morphological characteristics and Pa and Ps bars. Ps and Pa bars were classified as complete or incomplete (partial) depending on the degree of ossification. The complete Ps and Pa bars' anteroposterior diameter and craniocaudal diameter were measured. The closest distance between both bony prominences was measured in incomplete Ps and Pa bars. Sex-dependent statistical analysis of the data was performed by the SPSS package program (version 25.0). The prevalence of Ps was 6.57%, and unilateral incomplete Ps was the most frequent Ps type at 5%. The prevalence of Pa was 16.28%, and unilateral incomplete Pa was the most common Pa type at 6.71%. The prevalence of unilateral Ps, unilateral, and bilateral Pa was more common in males (P = .014, P = .006, and P = .032, respectively). Although Ps were less frequently encountered, both anatomic variations were relatively common within the population. The prevalence and morphometric characteristics of Ps and Pa bars obtained in this study could serve as guiding insights for the practices of surgeons, anesthesiologists, dentists, and radiologists.

A morphological study on the sphenoid bone ligaments' ossification pattern

PURPOSE

The sphenoid bone (SB) extracranial ligaments (ECRLs) are the pterygoalar and pterygospinous ligaments (PTAL and PTSL) that are located at the SB lateral pterygoid plate, and inferior to the foramen ovale (FO). Their ossification may affect the mandibular nerve's distribution. The intracranial ligaments' (ICRLs) ossification (the caroticoclinoid ligament-CCLL, the anterior and posterior interclinoid ligaments-AICLL and PICLL) may impede the approaches to the sella. This study highlights the incidence of the ossified ECRLs and ICRLs location, their type (partial, or complete), considering laterality, gender, age, and ligaments' simultaneous presence.

METHODS

The sample consisted of 156 Greek adult dried skulls of both genders and variable age.

RESULTS

Ossified ligaments were identified in 57.05%, predominantly extracranially (42.31%, P = 0.003). ECRLs were predominantly identified unilaterally (30.13%, P < 0.001). The majority of the ossified ICRLs were predominantly identified in male skulls (31.1%, P = 0.048) and the majority of the ECRLs (52.8%, P = 0.028) were predominantly identified at the age of 60 years and above. The PTAL was the most ossified (32.69%), followed by the CCLL (24.36%), the PTSL (16.03%), the PICLL (6.41%), and the AICLL (4.49%).

CONCLUSIONS

Detailed knowledge of the SB morphology and ligaments' ossification extent is essential to improve the technique of the FO percutaneous approach, and sellar approaches, to minimize complications.

Successful percutaneous cannulation of foramen ovale obstructed by completely ossified pterygoalar ligament using the Hartel approach: Two case reports

RATIONALE

Ossification of the pterygoalar ligament, which lies inferolateral to the exocranial opening of the foramen ovale, is traditionally considered to be a bony bar that could obstruct percutaneous needle access to the foramen ovale using the Hartel approach. We herein present two case reports of successfully penetrating the foramen ovale by a needle across the pterygoalar bar. Lack of knowledge of this type of presentation might lead to a change in the surgical approach.

PATIENT CONCERNS

A 27-year-old woman had an 11-year history of facial pain because of a space-occupying lesion in the left cerebellopontine angle. Neither open surgery nor drug therapy resolved her facial pain. Another 67-year-old woman developed episodic facial pain because of herpes zoster infection 20 days earlier, and she could not achieve pain relief from drug therapy.

DIAGNOSES

Both patients were diagnosed with secondary trigeminal neuralgia.

INTERVENTIONS

The patients underwent radiofrequency thermocoagulation of the semilunar ganglion via the foramen ovale.

OUTCOMES

The three-dimensional computed tomography scan showed that the ipsilateral foramen ovale was obstructed by the pterygoalar bar. However, percutaneous needle cannulation of the foramen ovale was successful using the anterior approach. The facial pain was immediately and completely resolved without complications except for facial numbness.

LESSONS

During percutaneous radiofrequency thermocoagulation for the treatment of trigeminal neuralgia, the Hartel approach can still be used when the foramen ovale is blocked by a pterygoalar bar. To our knowledge, this is the first report of such a treatment. Moreover, we herein provide specific technical recommendations to assist surgeons who may encounter such cases in the future.

Development of pre-procedure virtual simulation for challenging interventional procedures: an experimental study with clinical application

Background

Most pain management techniques for challenging procedures are still performed under the guidance of the C-arm fluoroscope although it is sometimes difficult for even experienced clinicians to understand the modified three-dimensional anatomy as a two-dimensional X-ray image. To overcome these difficulties, the development of a virtual simulator may be helpful. Therefore, in this study, the authors developed a virtual simulator and presented its clinical application cases.

Methods

We developed a computer program to simulate the actual environment of the procedure. Computed tomography (CT) Digital Imaging and Communications in Medicine (DICOM) data were used for the simulations. Virtual needle placement was simulated at the most appropriate position for a successful block. Using a virtual C-arm, the authors searched for the position of the C-arm at which the needle was visualized as a point. The positional relationships between the anatomy of the patient and the needle were identified.

Results

For the simulations, the CT DICOM data of patients who visited the outpatient clinic was used. When the patients revisited the clinic, images similar to the simulated images were obtained by manipulating the C-arm. Transforaminal epidural injection, which was difficult to perform due to severe spinal deformity, and the challenging procedures of the superior hypogastric plexus block and Gasserian ganglion block, were successfully performed with the help of the simulation.

Conclusions

We created a pre-procedural virtual simulation and demonstrated its successful application in patients who are expected to undergo challenging procedures.

Anatomical relationship between the foramen ovale and the lateral plate of the pterygoid process: application to percutaneous treatments of trigeminal neuralgia

Our aim was to clarify the variations in the positional relationship between the base of the lateral plate of the pterygoid process and the foramen ovale (FO), which block inserted needles during percutaneous procedures to the FO usually used for the treatment of trigeminal neuralgia. Ninety skulls were examined. The horizontal relationship between the FO and the posterior border of the base of the lateral plate of the pterygoid process was observed in an inferior view of the skull base. Skulls that showed injury to either the FO or the lateral plate of the pterygoid process on either side were excluded. One hundred and sixty sides of eighty skulls were eligible. The relationship between the FO and the posterior border of the base of the lateral plate was classified into four types. Among the 160 sides, type III (direct type) was the most common (35%), followed by type I (lateral type, 29%) and type IV (removed type, 21%); type II (medial type) was the least common (15%). Of the 80 specimens, 53 showed the same type bilaterally. In type IV, the posterior border of the base of the lateral plate is disconnected from the FO, so percutaneous procedures for treating trigeminal neuralgia could fail in patients with this type.

Pterygospinous and pterygoalar bars in children

PURPOSE

The formation of pterygoalar (Pa) and pterygospinous (Ps) bars are controversial whether they are secondary ossifications with aging or phylogenetic remnant. Therefore we aimed to evaluate the presence of Pa and Ps bars in children on routine cranial computed tomography images.

METHODS

We retrospectively analyzed the cranial computed tomography images of 500 children under the age of 18. Besides the 0.5 mm axial images, maximum intensity projection and 3D reconstructions were also used. The existence of incomplete or complete Pa and Ps bars were investigated.

RESULTS

Incomplete and complete Pa bar was detected in 4.6% and 2.2% of the cases, respectively. Incomplete Ps bar was seen in 13.6% of the cases and complete was in 6%. In total, per 1000 sides, 12 (2.4%) complete and 27 (5.4%) incomplete Pa bars were detected. In the same way, 35 (7%) complete and 88 (17.6%) incomplete Ps bars were seen. The smallest age ossification detected was 5 months old. Additionally, the prevalence of Pa and Ps bars between the under and over 10 years old age groups were statistically significant. Aging increased the prevalence.

CONCLUSION

Considering our results, it seems that the ossification of Pa and Ps ligaments may not be solely related with aging.