The size of the foramen ovale regarding to the presence and absence of the emissary sphenoidal foramen: is there any relationship between them?

Foramen ovale morphology and relationship with the lateral pterygoid process plate: proposal for a new classification system

Surgeons frequently approach the foramen ovale (FO) via the infratemporal fossa (ITF) to treat trigeminal neuralgia. However, this percutaneous procedure could be unsuccessful due to anatomical factors. The present study aimed to assess the FO morphology and its relationship with the lateral pterygoid process plate (LPPP), emphasizing coexisting ITF variants. One-hundred-and-eight (216 sides) adult dried skulls were evaluated at the ITF (FO and LPPP). The FO maximum anteroposterior and lateromedial distances (APD and LMD) were calculated and correlated with the FO morphology. The FO-LPPP relationship was observed, and the presence of a sphenoidal emissary foramen (SEF) and possible ossified sphenoid bone's ligaments variants (pterygoalar and pterygospinous-PTA and PTS variable ossification) were recorded. Statistical analysis was performed using the SPSS statistical program. The FO morphology was classified into three types after taking into consideration the FO morphometry. Type 1 FO was considered when the APD was two times more than the LMD (45.83%), Type 2 FO was identified when the APD was more than the LMD but no more than two times (51.85%), and Type 3 FO was considered when the APD and LMD were equal (2.32%). The FO and LPPP relationships were classified into the following four types: the direct type when the LPPP base ended at the FO center (32.3%), the lateral type was observed when the LPPP base ended at the FO lateral margin (28.76%), the far type was considered when the LPPP base ended distally to the FO (22.57%), and the medial type was when the LPPP base ended at the FO medial margin (11.95% of cases). Concerning the impact of the sphenoid bone variants on the FO-LPPP, the SEF did not alter the FO-LPPP relationship, while the PTA or PTS bar presence significantly affected it (p < 0.001 and p = 0.007, respectively). When the sphenoid bone ossified bars were present, the most common type of FO was the medial one. A novel classification system was proposed for the FO morphology, assessing possible coexisting ITF variants that could alter the FO-LPPP relationship. Knowledge of these details would help clinicians perform percutaneous procedures to treat trigeminal neuralgia.

An accessory sphenoidal foramen of the middle cranial fossa detected on computed tomography

BACKGROUND

The skull base depicts significant morphological variability, which is frequently described due to its neurosurgical significance. The middle cranial fossa's accessory foramen has rarely been described.

MATERIALS

A 53-year-old female patient's computed tomography (CT) scan was further investigated for its unusual morphology.

RESULTS

On the left-sided middle cranial fossa, an accessory sphenoidal foramen (ASF) was observed, located 3.3 mm posterior to the foramen rotundum (FR) and 5.5 mm anterior to the foramen ovale (FO). Extracranially, the ASF opened into the infratemporal fossa and coexisted with another sphenoidal emissary foramen (SEF), anteromedially to the FO. On the right side, two SEF were located anteromedially to the FO.

CONCLUSIONS

Similar to the current case, ASF of the middle cranial fossa were reported in a previous study with a prevalence of 0.20%. The unconstraint well described accessory foramina are the emissary foramina that transmit emissary veins, and are of interest for anatomists, radiologists and neurosurgeons.

The sphenopterygoid canal and pterygoid foramen

BACKGROUND

In human anatomy, there are well-known the foramina of the greater sphenoidal wing, the foramen rotundum, the foramen ovale, the foramen spinosum, as well as the inconstant sphenoidal emissary foramen of Vesalius and the foramen of Arnold. Different canals are found in several species of rodents, such as the alisphenoid and sphenopterygoid (SPC) canals.

METHOD

It was re-explored an archived computed tomography angiogram of a 60 y.o. female case.

RESULTS

Bilateral superior recesses of the pterygoid fossae (SRPF) and a right SPC were found. The SRPF on each side penetrated the non-lamellar pterygoid root and superiorly reached the sphenoidal sinus wall. Upper fibres of medial pterygoid muscles were inserted into each SRPF. An unexpected SPC was found on the right side. It opened superiorly on the lateral side of the foramen rotundum and inferiorly at a pterygoid foramen in the superior end of the posterior margin of the lateral pterygoid plate. A sphenoidal emissary vein traversed that SPC to drain into the pterygoid plexus.

CONCLUSION

The SRPF and SPC could also be found in humans. As the sphenoidal emissary veins are surgically relevant, they should not be further regarded as exclusively crossing the foramen of Vesalius but also the SPC.

Foramen venosum: a clinicoanatomic insight into its occurrence and morphometry

PURPOSE

The present study aimed to evaluate the foramen venosum (FV) frequency, incidence, morphometry and relation with foramen ovale in an Indian population. The emissary vein passing through it may spread extracranial facial infections to the intracranial cavernous sinus. Due to its close proximity with the foramen ovale and its variable occurrence, awareness about its presence and anatomy is essential to neurosurgeons operating in this region.

METHODS

62 dry adult human skulls were studied for the occurrence and morphometry of foramen venosum, both at the middle cranial fossa and extracranial base of the skull. Dimensions were taken using Java-based image processing program, IMAGE J. After collection of data, appropriate statistical analysis was done.

RESULTS

The foramen venosum was observed in 49.1% skulls. Its presence was noted more frequently at the extracranial skull base than in the middle cranial fossa. No significant difference was observed between the two sides. FV at the extracranial view of the skull base had a larger maximum diameter than in the middle cranial fossa; however, the distance between FV and the foramen ovale was found to be more at the middle cranial fossa than at the extracranial view of the skull base on both the right and left side. Variations in the shape of the foramen venosum were also observed.

CONCLUSION

The present study is not only of great importance to anatomists, but also to radiologists and neurosurgeons for better planning and execution of the surgical approach to the middle cranial fossa through the foramen ovale to prevent iatrogenic injuries.

Sphenoidal Foramen Ovale in the Slovenian Population: An Anatomical Evaluation with Clinical Correlations

The foramen ovale (FO) is a crucial feature of the skull base, serving as a passage for clinically important neurovascular structures. The present study aimed to provide a comprehensive morphometric and morphologic analysis of the FO and highlight the clinical significance of the anatomical characterization. A total of 267 FO were analyzed in skulls obtained from deceased inhabitants of the Slovenian territory. The anteroposterior (length) and the transverse (width) diameters were measured using a digital sliding vernier caliper. Dimensions, shape, and anatomical variations of FO were analyzed. The mean length and width of the FO were 7.13 and 3.71 mm on the right side and 7.20 and 3.88 mm on the left side. The most frequently observed shape was oval (37.1%), followed by almond (28.1%), irregular (21.0%), D-shaped (4.5%), round (3.0%), pear-shaped (1.9%), kidney-shaped (1.5%), elongated (1.5%), triangular (0.7%), and slit-like (0.7%). In addition, marginal outgrowths (16.6%) and several anatomical variations were noted, including duplications, confluences, and obstruction due to a complete (5.6%) or incomplete (8.2%) pterygospinous bar. Our observations revealed substantial interindividual variation in the anatomical characteristics of the FO in the studied population, which could potentially impact the feasibility and safety of neurosurgical diagnostic and therapeutic procedures.

The sphenoidal emissary foramina prevalence: a meta-analysis of 6,369 subjects

PURPOSE

To estimate the prevalence of the sphenoidal emissary foramina (SEF), and the effect of possible moderators on it.

METHODS

A systematic online literature search was conducted. The pooled prevalence with 95% confidence intervals was estimated. Outlier and influential analyses were performed. The presence of small-study effect and publication bias were evaluated. Moderator analyses were executed to investigate the effect of the specimens' continent of origin, type of study (dried skull or imaging), probing for the evaluation of SEF patency (conduction and instruments used), side dominance (bilateral or unilateral), morphometric data [SEF diameter, distances SEF-Foramen ovale (FO) and SEF-Foramen spinosum (FS)], and the methodology used for the morphometric measurements (caliper, DICOM Viewer, and image analysis software) on the estimated prevalence.

RESULTS

In total, 6,460 subjects from 26 studies were included in the meta-analysis. The overall SEF prevalence was estimated as 38.1%. The heterogeneity was high and statistically significant. No indications of publication bias and small-study effect were identified. The conducted subgroup analyses did not yield statistically significant differences in the SEF prevalence between groups, except of the type of side dominance. Both results of the univariable and multivariable regression analyses showed the association of the unilateral dominance with a decrease in the reported SEF prevalence.

CONCLUSION

The identification of more unilateral than bilateral foramina in a given cohort is associated with a decrease in the reported crude SEF prevalence. Laterality-specific estimates should be established for a precisive estimation of the emissary foramina prevalence.

Anatomical dimensions and variances of the foramen ovale in adult human skulls

Background/Aim: The foramen ovale (FO) is very important in neurosurgical approaches; however, studies and developments in the literature report that no definite consensus about the cannulation of the FO is available. Therefore, more morphometric information concerning the FO is needed in addition to the previously defined morphological and morphometric features. The aim of this study was to compare the features of the foramen ovale stated in the literature and to analyze the topographic relationship between the FO and the anatomical structures around it to determine its precise location. Methods: The study included 70 sides from 35 dry skulls of unknown age and gender. Skulls with any deformity or pathology that would affect the measurements were not included in the study. All skulls were placed in the horizontal plane with the external occipital protuberance facing posteriorly, the piriform aperture facing anteriorly, and the skull base pointing upwards at a 90° angle after which it was photographed vertically with the length scale. A Nikon D5300 Digital Camera was used for the photography, and digital image processing software (Image J) was used for foramen ovale measurements. In addition, the shape of the foramen ovale was classified as oval, almond, D-shaped, slit-shaped, round, and irregular. SPSS 21.0 was used for the statistical analysis. Results: The mean anteroposterior diameter length of the FO was 6.144 mm, and the transverse diameter length was 2.885 mm. When the distribution of the shape of the FO was examined, oval and almond shapes were most common shapes (34.29%). In addition, round (12.85%), D-shaped (10%), and slit-shaped (8.57%) were obtained. According to Pearson’s correlation analysis, the highest correlation was between the distance from the carotid canal to the foramen ovale and the shortest distance from the foramen ovale to the midline (FO-CC and the FO-ML, respectively; r = 0.427). Conclusion: The morphology of the FO is important in terms of surgical and interventional approaches. In the literature, no significant differences between the right and left sides for the foramen ovale were found in contrast to our study. When the FO shape percentages were examined in most previous studies, it was seen that most of them were oval. In this study, the ratios of oval and almond shapes were the same. Morphometric measurements can give different results in every race due to the structure of the bones, which may vary according to the population. We think that presenting data on the Turkish population in this study will set an example for conducting future studies.

The emissary veins of the foramen ovale: an anatomical study using magnetic resonance imaging

PURPOSE

The emissary veins (EVs) passing through the foramen ovale (FO) are not well understood. The aim of this study was to characterize these veins using contrast magnetic resonance imaging (MRI).

METHODS

In total, 85 patients underwent thin-sliced, contrast MRI. Coronal and sagittal images were used for the analysis.

RESULTS

The EVs of the FO were well delineated in 100% on sagittal and 97% on coronal images. On the sagittal images, these veins could be classified into the lateral, medial, and perineural types in association with the mandibular division of the trigeminal nerve (V3) segment in the FO. In 22% of the slides, the medial EV was more predominant than lateral one, while in 64% of the slides, the latter was more predominant. On the coronal images, the identified EVs of the FO coursed medially to the V3 in 68% and laterally in 72% of 165 sides. The perineural EVs most frequently coursed along both the lateral and medial surfaces of the V3. On the sagittal images, the angles formed by the midline of the V3 segment in the FO and lower margin of the FO were 81.5 ± 11.9° on the left side and 80.0 ± 12.2° on the right, while on the coronal images, they were 61.5 ± 12.1° on the left side and 64.8 ± 11.3° on the right.

CONCLUSIONS

The EVs of the FO are structures that may be characterized by a well-developed venous channel in the lateral aspect of the V3 and nearly symmetrical orientation of both V3s lying in the FO.