|Year : 2022 | Volume
| Issue : 1 | Page : 10-16
Sexual dimorphism and clinical importance of posterior condylar canal
Sushant Swaroop Das
Assistant Professor, Department of Anatomy, Shyam Shah Medical College, Rewa, Madhya Pradesh, India
|Date of Submission||17-May-2021|
|Date of Decision||31-Jul-2021|
|Date of Acceptance||08-Nov-2021|
|Date of Web Publication||01-Feb-2022|
Sushant Swaroop Das
Department of Anatomy, Shyam Shah Medical College, Rewa, Madhya Pradesh
Source of Support: None, Conflict of Interest: None
Background: The posterior condylar canal (PCC) and its associated emissary vein are important anatomical landmarks for juxta-condylar approach and extreme lateral approach for exposing lesions in the region lateral to the foramen magnum. The study aimed to provide a complete gender-based assessment of the morphological characteristics of PCC in an adult central Indian population. Methodology: The study was conducted on 130 dry adult central Indian human skulls of known sex (81 males, 49 females). The presence of PCC on both sides, their patency, variations, and site of internal opening in relation to important anatomical landmarks, i.e., sigmoid sulcus, jugular foramen, and foramen magnum were assessed. Results: The PCC and probe patency were statistically more common bilaterally than unilateral. Females showed statistically significant higher incidence of bilateral PCC and bilateral probe patency than males. Three morphological variations in PCC were found, i.e., double condylar canal, septation, and spur. They showed no significant gender differences. In both sexes, bilateral intrasinus was the most common type of internal opening of PCC. Internal opening into jugular foramen, foramen magnum, and retro sinus was significantly more unilaterally than bilateral. Significant gender differences in unilateral intrasinus and unilateral retro sinus type of internal opening were noted. Conclusion: This study gives knowledge about the comparison of various morphological variations of PCC in both sexes of an adult central Indian population, and its clinical impact on the surgeries of this region.
Keywords: Arterio-venous fistula, emissary vein, foramen magnum, posterior condylar canal, occipital bone
|How to cite this article:|
Das SS. Sexual dimorphism and clinical importance of posterior condylar canal. Natl J Clin Anat 2022;11:10-6
| Introduction|| |
Posterior condylar canal (PCC) is the most frequently present emissary foramen in human skulls as well as the largest emissary foramen in the posterior cranial fossa., At the base of cranium, behind the occipital condyles there is a fossa called condylar fossa. During full extension at atlanto-occipital joint, the posterior margin of superior articular facet of atlas fits into this condylar fossa. Sometimes, this condylar fossa is pierced by a canal, called PCC or condylar canal. Its internal orifice is posterolateral to the internal opening of hypoglossal canal. In most cases, it transmits emissary vein from sigmoid sinus to vertebral vein present between the atlas and axis cervical vertebral bone or in some cases, between superior bulb of inter jugular vein and suboccipital venous plexus. A posterior condylar emissary vein may also communicate with the horizontal portion of vertebral artery venous plexus. Thus, the posterior condylar foramen provides one of the important channels of communication between intracranial and extracranial space. It also gives way to meningeal branch of occipital artery.,, During the growth of the jugular sinuses and gradual change from fetal to adult circulation, this venous passage through the PCC gradually atrophies. This venous atrophy is accompanied by the PCC closure; however, it may persist and enlarge in majority of the adult skulls. The PCC may be partially or fully patent. The cause may be linked to failure of normal development of the sigmoid-jugular complexes.,,
The clinical importance of this channel is that they provide a substitute channel for venous drainage in the cases of internal jugular vein obstruction, cerebral congestion, lesions of neck or skull base, thus helping in maintaining intracranial pressure in these conditions.,,,, It can also act as a pathway for the spread of infections. These emissary veins may get enlarged secondary to high-flow vascular malformations and when massively enlarged it may become one of the causes of pulsatile tinnitus., Variations in PCC may be associated with variations in posterior condylar vein which may be wrongly considered as pathological and may lead to unpredictable complications during intracranial procedures. The anatomical variations in emissary foramen were also found to be correlated with some diseases such as osteoporosis, osteopetrosis, neurofibromatosis, Cruzons syndrome, brachy microcephaly, and mental retardation.,,,, As the posterior condylar vein may be localized very closely with the tumors in the skull base or neck; the location, dilatation and variations of this vein should be identified before performing surgeries in the posterior cranial fossa and posterior cervical region. The PCC and posterior condylar emissary vein are also important anatomical landmarks for lateral foramen magnum surgical approaches.,, This knowledge may lead to change in the surgical approaches and may avoid intraoperative complications.
Most of the data present in previous studies on the PCC, assessed only the laterality factor.,,,,,,,, Therefore, there is paucity of literature on the sexual differences of PCC. The understanding of gender differences can be a big asset to the operating surgeon to make desirable changes in his clinical approaches. The present study was done with the objective to assess the prevalence, sexual dimorphism and anatomical variations of the PCC in an adult central Indian population.
| Materials and Methods|| |
This descriptive cross-sectional study was conducted on 130 dry adult central Indian human skulls of known sex (male: 81, female: 49) obtained from the osteology museum in the department of anatomy, Shyam Shah Medical College, Rewa, Madhya Pradesh. Study was conducted after seeking IEC approval (No. IEC 130, 9/6/2020). Skulls showing obscuring pathologies such as bone deterioration were omitted from the study. Sample size was calculated to be 129.61 using the formula: n = Z2 × P (1-P)/d2, where, n = sample size, Z = 1.96 for 95% confidence level, P = 0.907 (90.7%) expected prevalence taken from Goda et al. and d = 5% (precision).
The skulls were examined for the presence of PCC on both sides, their patency and site of internal opening. Patency was established by passing a metal probe (1 mm diameter) through the PCC into posterior cranial fossa. The internal opening of PCC was seen in relation to nearby important anatomical landmarks, i.e., sigmoid sulcus, jugular foramen, and foramen magnum. The presence of any variations of PCC was also observed. Photographs of skulls were taken with the help of Canon EOS 200D digital camera.
All the observations were recorded and statistical analysis was done using Chi-square test for nominal categorical data in SPSS (Statistical Package for the Social Science) Windows version 23.0 (IBM corp., Armonk, New York, USA) to evaluate the relationship between the examined variables. A level of significance of P < 0.05 was used. The observations and results were then tabulated and compared with earlier studies [Table 1], [Table 2], [Table 3].
|Table 2: Morphological variations and internal opening of posterior condylar canal|
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| Results|| |
The results of the present study are summarized in [Table 1] and [Table 2]. Of the 130 skulls, PCC was present in 119 (91.54%) (74 males [91.36%], 45 females [91.87%]) skulls [Figure 1]. The bilateral PCC was found statistically more common than the unilateral PCC. Males showed a higher incidence of unilateral and absent PCC as compared to females. In contrast, females showed a higher incidence of bilateral PCC than males [Table 1]. Unilateral PCC was seen in 31 male (38.27%) skulls and in 10 female (20.41%) skulls. This difference was statistically significant (P = 0.034). Rest all differences between the two sides and the two genders were statistically nonsignificant.
|Figure 1: Inferior view of skull base showing: (a) Bilateral posterior condylar canal; (b) Left side posterior condylar canal; (c) Bilateral absent posterior condylar canal|
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Bilateral probe patency of PCC was found statistically more common than unilateral. Unilaterally, males showed a higher percentage of probe patency than females. But bilaterally, females showed more percentage of probe patency than males [Table 2].
Three types of morphometric variations in PCC were noted in this study, i.e., double condylar canal, septation, and spur [Figure 2]. The double condylar canal divided the PCC into two complete canals which had separate internal and external openings. Septation was seen as a bony septum from roof to the floor of the canal. Spur was seen as a bony spicule projecting from the roof of the canal but not touching the floor. Both septation and spur divided the PCC partially so that they had a common internal or external opening.
|Figure 2: Inferior view of skull base showing: (a) Septation in left side posterior condylar canal (yellow arrow); (b) Double condylar canal (green arrow) and spur (red arrow) on right side posterior condylar canal|
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Both septation and spur were statistically more common unilaterally. Although males showed a higher incidence of these morphometric variations than females, statistically no significant difference was noted in these variations of PCC between the two genders.
The internal opening of PCC was classified into four types based on its location i.e., sigmoid sinus (intrasinus), jugular foramen, foramen magnum, and behind sigmoid sinus (retro sinus) [Figure 3]. No bilateral opening into jugular foramen or foramen magnum in both genders was noticed. Furthermore, right side unilateral opening into jugular foramen and unilateral opening (on either side) into foramen magnum was not seen in female skulls. The different types unilateral internal opening was found statistically more common than bilateral except in intrasinus type which was nonsignificant.
|Figure 3: Skull base showing sites of internal opening of posterior condylar canal: (a) Intrasinus on left side and jugular foramen on right side, (b) Foramen magnum on left side; (c) Foramen magnum on right side; (d) Retrosinus on left side; (e) Bilateral intrasinus|
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The most common internal opening in males was unilateral and bilateral intrasinus equally. And in females was bilateral intrasinus type. Significant gender differences in unilateral intrasinus and retro sinus type were noticed. Males showed a higher incidence of unilateral intrasinus opening. In contrast, females showed preponderance of unilateral retro sinus especially right side as compared to males.
| Discussion|| |
The varied anatomy of the PCC, the different origins and drainage of the emissary veins which pass through it, the variations in its morphology, as well as surgical approaches to this strategic part of the skull base, interests the minds of several neurosurgeons and radiologists.
The PCC is the largest and most frequent emissary foramina.,,, In the present study also, higher prevalence of PCC was found. This signifies that this structure is both anatomically and clinically important as it connects the intracranial dural venous sinuses with the extracranial venous channels. This higher prevalence of PCC was almost equally distributed between males (91.36%) and females (91.84%). Due to this significant prevalence of PCC in both males and females, surgeons during planning and execution of any surgical intervention in this region should consider any vascular abnormality related to PCC. Inadvertent procedure in the region may lead to serious intra cranial consequences like fistula or bleeding.
A wide range of minor variants of skull foramen including PCC is genetically determined and can be a useful anthropological tool. It could be used to calculate a distance statistic relationship between different population or races., Hauser and De Stefano also suggested that these cranial variants may be epigenetic as they are the products of genetically determined growth processes of tissues such as vessels, nerves, and muscles which affect the bone formation. Wide ethnic variations in the incidence of PCC have been reported in the literature from osteological specimens. Its prevalence ranged from 70.8%–90.6% in Americans,, 59%–76.9% in Europeans, 73.33%–90.7% in west Indian population,, and 86%–94.23% in south Indian population,, [Table 3]. Our data (91.54%) falls in the midst of the range reported in the osteological studies of west and south Indian populations but was more closer to the south Indian population. This data could help various researchers who are doing anthropological and genetical studies of India.
Ginsberg on gross examination of skulls observed that the PCC was bilaterally more common than unilaterally. The unilateral PCC were equally distributed between right and left side. Other studies also found a higher incidence of PCC bilaterally than unilaterally.,,,,, Many American, and European studies reported unilateral PCC is present more often on the right side than on the left. This reported right-sided dominance of the PCC was not holding up by our findings. In the present study, there was a dominance of bilaterally present PCC than unilateral. Probe patency was also found more common bilaterally than unilaterally which also reinforces this finding related to the predominance of bilateral PCC. When the foramen was unilateral, a slightly higher orientation was seen on the left side than the right. Most of the studies on south Indian population also showed a similar higher preponderance of left side PCC than right.,, In contrast, studies on west Indian population showed the opposite., Thus, this finding also supports our previous finding that the central Indian population may be genetically more closer to the south Indian population than the west Indian population.
In our study, males showed a significant higher incidence of unilateral PCC and unilateral probe patency as compared to females. In contrast, females showed a significant higher incidence of bilateral PCC and bilateral probe patency than males. Therefore, PCC is a more bilaterally consistent finding in females than males. During embryological development, there is a gradual shift from fetal to adult circulation, and the venous passage through the PCC gradually atrophies. This venous atrophy is accompanied by the PCC closure; however, it may persist and enlarge in a majority of the adult skulls.,, Thus, our findings suggest that this type of bilateral venous atrophy may happen more often in males as compared to females which led to a higher incidence of bilateral PCC in females.
Our study reported the highest incidence of three types of morphological variations of PCC in the central Indian population, i.e., double condylar canal, septation, and spur as compared to other global population studies [Table 3]. These three variations represent the stages linked to failure of normal development of the sigmoid-jugular venous complexes. Among these, the spur was the most common variation. Overall, these variations together were more common unilaterally than bilaterally especially the septation and spur. The most common morphological variation noted in males was the left-side unilateral spur and in females was the right-side unilateral spur. No significant sexual differences were noted but there was a general male dominance in these variations which could suggest that failure of normal development of the sigmoid-jugular venous complexes may be more common in males than females.
Most of the osteological studies reported only two sites of internal opening of PCC, i.e., intrasinus (into sigmoid sulcus) and retro sinus (behind sigmoid sulcus).,,, However our study found four sites of internal opening of PCC i.e., intrasinus, retro sinus, jugular foramen, and foramen magnum. The most common location was the intrasinus type which was in accordance with most of the previous studies. The intrasinus type was bilaterally more common than unilateral but the rest of all types were statistically more common unilaterally [Table 2]. This shows that whenever there is a failure of normal development of the sigmoid-jugular venous complexes leading to variant opening of PCC, it occurs more often unilaterally.
In males and females separately, bilateral opening into sigmoid sulcus (intrasinus type) was the most common location. However, in total cases of unilateral intrasinus type, males showed significant higher incidence than females. Unilateral retro sinus type especially the right-side retro sinus unilateral opening were significantly more common in females than males. This suggests that in males, failure of normal development of sigmoid-jugular venous complexes most commonly leads to unilateral intrasinus type of internal opening and it leads to unilateral retro sinus type of internal opening, especially on the right side.
Overall intrasinus and foramen magnum type were more common in males; retro sinus especially and jugular foramen type were more common in females as compared to their respective opposite gender. The males overall showed more types of variations in internal opening of PCC than females as the internal opening into foramen magnum was not seen in female skulls. In addition, bilateral opening into jugular foramen was not seen in both genders suggesting that this type of bilateral variation may be very rare or absent in the adult central Indian population. These sexual variations in internal opening of PCC add to our previous finding that failure of normal development of the sigmoid-jugular venous complexes happens more often in males as compared to females. These gender differences of PCC found in this study could not be related to the previous studies, as there was a paucity of literature regarding this type of gender assessment of PCC. Therefore, this study could provide a baseline data of gender assessment for PCC in the adult central Indian population which can, later on, form a building block for studies on other global populations.
The PCC and its associated emissary vein are of great importance in the surgical treatment of tumors and dural arteriovenous fistulas in this region. They act as important anatomical landmarks to differentiate the transcondylar fossa approach from the transcondylar approach which prevents the avoidable injury to the atlanto-occipital joint. They have also been used as potential landmarks for posterolateral approaches for exposing lesions in the region of jugular foramen and hypoglossal canal, such as the juxta-condylar approach and extreme lateral approach.,, The posterior condylar veins can be used as entry routes to hypoglossal dural arteriovenous fistulas and transverse-sigmoid dural arteriovenous fistulas with obstruction of the jugular vein. In addition, the dural arteriovenous fistulas can involve these condylar veins also., Clinically also, it represents an alternative source of venous drainage from the intracranial to the extracranial venous system, therefore, acting as a route of transmission of infections. The variable patterns and the gender differences of PCC may therefore affect these surgical interventions around the occipital region. The higher consistency of PCC in females as compared to males makes it a more reliable, potential landmark in females than males. Therefore, we have to look for other landmarks also other than PCC in males during the planning of these above-mentioned surgical approaches. Also due to higher incidences of morphological variations of PCC in males as compared to females, surgeons have to be more cautious in males as these variations could be a hindrance to the endovascular procedures. The knowledge of different predominance of the internal opening of PCC in both the sexes will also help to decide the entry routes for this endovascular intervention.
Thus, knowledge of normal anatomy and gender variations of PCC may be useful for neurosurgeons during differential planning and execution of surgical procedures around the occipital region in both sexes. Recognizing this anatomical structure and its variations in imaging studies will prevent misinterpretation of radiological scans as it can be confused with glomus jugulare tumor or calcified lymph node.,, Since the morphological variations of the cranial foramina could be a consequence of many diseases or other extrinsic factors such as osteoporosis, osteopetrosis, neurofibromatosis, Cruzons syndrome, brachy microcephaly, and mental retardation;,,,, the gender variations noted in our study can also help in better understanding of the gender influences on these diseases.
| Conclusion|| |
The present study concludes a complete gender-based assessment of PCC in the adult central Indian population which could help in understanding the different embryological developmental processes related to sigmoid-jugular complexes in both sexes. The morphologic data and variations observed in the present study are of immense value to the neurosurgeons while performing skull base surgeries or endovascular treatment in both sexes for arteriovenous fistula in the region around the occipital condyle.
The authors sincerely thank those who donated their bodies to science so that anatomical research could be performed. Results from such research can potentially increase mankind's overall knowledge that can then improve patient care. Therefore, these donors and their families deserve our highest gratitude.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]