Abstract
Introduction
Idiopathic intracranial hypertension is a condition characterized by elevated intracranial pressure in the absence of an intracranial mass lesion and is commonly associated with neuro-ophthalmic symptoms. Although venous outflow abnormalities, particularly transverse sinus stenosis, have been extensively investigated in idiopathic intracranial hypertension, the potential role of jugular foramen volume has not been previously studied. Considering that major venous structures pass through the jugular foramen, this study aimed to evaluate whether jugular foramen volume plays a role in the development of idiopathic intracranial hypertension.
Methods
Forty patients who were diagnosed and followed up for idiopathic intracranial hypertension according to the modified Friedman criteria were included in the study. A control group of 40 individuals without idiopathic intracranial hypertension was randomly selected from the same archive. Jugular foramen volumes were measured using cranial computed tomography scans retrieved from the institutional archive. Age, sex, and bilateral jugular foramen volumes were recorded.
Results
No statistically significant differences were found between the idiopathic intracranial hypertension and control groups regarding right, left, or total jugular foramen volumes. The mean right jugular foramen volume was 1.574 ± 0.407 cm³ in the idiopathic intracranial hypertension group and 1.538 ± 0.308 cm³ in the control group; the mean left jugular foramen volumes were 1.474 ± 0.316 cm³ and 1.471 ± 0.246 cm³, respectively. No significant association was observed between jugular foramen volume and the development of idiopathic intracranial hypertension (p = 0.7438).
Conclusion
Jugular foramen volume does not appear to contribute to the development of idiopathic intracranial hypertension. This finding suggests that venous abnormalities associated with idiopathic intracranial hypertension are functional rather than related to static bony anatomy. Further studies with larger cohorts and detailed compartment-based anatomical assessments are warranted.
Keywords
Introduction
Idiopathic intracranial hypertension (IIH), characterized by high intracranial pressure in the absence of a space-occupying lesion, is a condition associated with neuro-ophthalmic symptoms. 1 The prevalence of IIH is 0.9/100,000. 2 The clinical presentation is heterogeneous. Headache, dizziness, neck and back pain, pulsatile tinnitus, visual loss, and diplopia may occur. IIH most commonly affects women aged 20–40 years, and a strong association with obesity has been reported. 3
The jugular foramen is located between the lateral border of the occipital bone at the base of the skull and the inferomedial part of the petrous pyramid. It extends anteriorly, laterally, and inferiorly, connecting the posterior fossa to the upper cervical region. 4 The passage of the cranial nerves and large venous structures through this foramen increases its importance.
The cerebral venous system is a network defined as two primary systems working together, the superficial venous system and deep venous system. 5 Both superficial and deep venous networks eventually drain into the internal jugular veins, brachiocephalic vein, and then into the right atrium via the superior vena cava. Several studies have investigated the role of cerebral venous drainage in the pathophysiology of IIH.
Recent studies have suggested that venous outflow abnormalities contribute to increased intracranial pressure by impairing cerebrospinal fluid (CSF) absorption and altering cranial venous compliance. Transverse sinus stenosis, jugular vein narrowing, and extrinsic compression of venous structures have been increasingly emphasized as potential contributors to IIH pathogenesis. Several imaging-based studies have demonstrated that even subtle anatomic variations in venous drainage pathways may significantly influence intracranial pressure dynamics, highlighting the importance of venous anatomy in the development of IIH.
Although transverse sinus and internal jugular vein pathologies have been extensively examined in IIH research, the role of the jugular foramen itself has rarely been evaluated despite being a key transition point for intracranial venous return. Variations in jugular foramen morphology, particularly size asymmetries and compartmental differences (pars venosa vs. pars nervosa), may theoretically affect intracranial venous drainage. However, the potential association between jugular foramen volume and IIH has not been clearly defined in the existing literature, and very few studies have attempted volumetric measurements of the jugular foramen in a clinical setting.
Therefore, in the present study, we investigated whether jugular foramen volume differs between patients with IIH and healthy controls, and whether this anatomical parameter is associated with disease development.
Materials and methods
In our study, 40 patients aged 20–45 years who were evaluated at our institution and diagnosed with IIH according to the modified Friedman criteria 6 were included. All patients fulfilled these criteria, including the presence of symptoms and signs of raised intracranial pressure, normal neuroimaging excluding secondary causes, and elevated CSF opening pressure with normal CSF composition. Patients were included consecutively based on diagnostic eligibility, without sex-based stratification, to avoid selection bias in this anatomically focused study. Jugular foramen volumes of these patients were measured using cranial computed tomography (CT) scans obtained from the hospital archives (Group A, Table 1). A control group (Group B, Table 2) consisting of 40 individuals without IIH was randomly selected from the same archive. Control participants underwent cranial CT for non–IIH-related indications such as mild head trauma, headache evaluation without intracranial pathology, and nonspecific neurological complaints and had no clinical or radiological evidence of intracranial hypertension. Age, sex, and bilateral jugular foramen volumes were recorded. Measurements were performed using GE Volume Viewer Voxtool 4.7 (Chicago, IL, USA) (Figure 1).
Patients with idiopathic intracranial hypertension (Group A).
M: male; F: female; JFV: jugular foramen volume.
Control group (Group B).
M: male; F: female; JFV: jugular foramen volume.
Axial cranial CT images demonstrating jugular foramen segmentation. The jugular foramen is highlighted in green to illustrate the region-of-interest used for volumetric analysis. Coronal and sagittal multiplanar reconstructions were used to confirm anatomical orientation and accurate delineation of the foramen boundaries. Volumetric measurements were performed using GE Volume Viewer Voxtool 4.7 (Chicago, IL, USA) with semi-automatic segmentation and manual correction to ensure anatomical accuracy. CT: computed tomography.
Imaging protocol
All CT scans were obtained using a standard bone algorithm with a slice thickness of 0.625 mm. Images were reconstructed using high-resolution bone filters suitable for three-dimensional (3D) segmentation. Anatomical boundaries of the jugular foramen were identified in axial, coronal, and sagittal planes prior to volumetric measurement. Coronal and sagittal images were obtained using multiplanar reconstruction (MPR) from the original axial CT dataset.
Volumetric segmentation technique
Jugular foramen volume was calculated using the semi-automatic 3D region-of-interest (ROI) function of GE Volume Viewer Voxtool 4.7. Volumetric measurements were performed on axial CT images with a slice thickness of 0.625 mm, using 10 consecutive axial slices encompassing the anatomical midpoint of the jugular foramen. MPR (axial, coronal, and sagittal planes) was used to confirm anatomical localization (Figure 2).
Multiplanar demonstration of the jugular foramen localization used for volumetric analysis.
The segmentation process included the following:
Manual outlining of the foramen’s cortical margins on consecutive axial slices Automatic 3D interpolation using the software Final manual correction to ensure anatomical accuracy
The volume was expressed in cubic centimeter (cm³). Only total jugular foramen volume was evaluated; the pars venosa and pars nervosa compartments were not measured separately. No smoothing or artifact-reducing filters were applied to prevent bias in bony boundary determination.
Observer reliability and blinding
Measurements were performed independently once per patient by a neurosurgeon and a neuroradiologist. Intraclass correlation coefficients (ICCs) ranged between 0.87 and 0.92, indicating excellent interobserver agreement. Discrepancies >5% were re-evaluated and resolved by consensus. Both observers were blinded to group allocation.
Statistical analyses
Normality of continuous data was assessed using the Shapiro–Wilk test. Depending on distribution, variables were expressed as mean ± standard deviation (SD) or median (minimum–maximum) values. Group comparisons were performed using unpaired Student’s t-tests or Mann–Whitney U test, where appropriate; chi-square tests were performed for categorical variables. Effect sizes (Cohen’s d) were calculated using standard thresholds to evaluate the magnitude of differences, independent of the sample size. Post-hoc power analysis was conducted to determine whether the sample provided sufficient power to detect clinically meaningful differences. Statistical significance was set at p < 0.05. Analyses were performed using Statistical Package for Social Sciences (SPSS) software (version 22.0, IBM Corp., Armonk, NY, USA).
This retrospective study was conducted in accordance with the Declaration of Helsinki (1975, revised in 2024), and the reporting of the study conforms to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. 7
This study was approved by the Non-Interventional Research Ethics Committee of Fırat University (Document Date and Number: 01.11.2024–28577). All patient data were fully deidentified prior to analysis, and due to the retrospective design of the study, individual informed consent was not required.
Results
Group A included 21 women and 19 men, and Group B included 20 women and 20 men. No significant difference was found in the sex distribution between the two groups (p > 0.05).
The median age of Group A was 33 years, while that of Group B was 33 years. No significant correlation was observed between age and jugular foramen volume in both groups (p > 0.05).
The right jugular foramen volume was larger than the left in 22 patients of Group A and 26 patients of Group B. Although the right-side volume was greater in both groups, no significant difference was found in the right jugular foramen volumes of the two groups (1.574 ± 0.407 cm³ in Group A vs. 1.538 ± 0.308 cm³ in Group B; p = 0.659). Additionally, there was no significant difference in the left jugular foramen volume between the two groups (1.474 ± 0.316 cm³ in Group A vs. 1.471 ± 0.246 cm³ in Group B; p = 0.969).
The total jugular foramen volume was not significantly different between the two groups (3.048 ± 0.534 cm³ in Group A vs. 3.009 ± 0.507 cm³ in Group B; p = 0.7438). Effect size analysis demonstrated small and clinically negligible differences between the two groups (Cohen’s d <0.20 for all volumetric comparisons). These findings indicated no significant relationship between the jugular foramen volume and IIH development (Tables 1, 2, and 3).
Volumetric comparison tables (Group A and Group B).
JFV: jugular foramen volume; NS: not significant.
Discussion
Although IIH is not fully understood, its association with obesity and female sex is notable. In addition, irregular CSF dynamics and increased venous drainage disorders are among the other factors discussed.
The jugular foramen is an important anatomical structure that allows the majority of the venous blood in the head to be drained to the extracranial area.8,9 It has been reported that in patients with IIH, problems with intracranial venous drainage may play a role in disease progression. 9 Some studies have suggested that narrowing or occlusion of the jugular veins, in particular, contributes to increased intracranial pressure. 10 However, there is a paucity of studies that have investigated the direct effect of jugular foramen volume and assessed whether it plays a role in IIH development.
The jugular foramen is anatomically divided into two compartments. The larger posterolateral compartment is called the pars venosa, and the smaller anteromedial compartment is called the pars nervosa. 4 A fibrous or bony septum separates both compartments. The internal jugular vein, which is the main venous drainage of the brain, begins at the posterior part of the jugular foramen as a continuation of the sigmoid sinus and passes into the neck. As the jugular foramen is a critical transition point in the venous return system of the brain, narrowing of this bony canal may elevate intracranial pressure by altering venous outflow and sinus hemodynamics. Based on this anatomical rationale, we hypothesized that the jugular foramen volume influences the development of IIH. Considering this basic hypothesis, we compared the jugular foramen volume of the IIH and control groups and found no statistically significant difference.
The volume of the jugular foramen varies between the right and left sides in the same individual. It has been reported that 70%–80% of individuals demonstrate either symmetric jugular foramina or right-sided dominance. 4 This difference, which mainly concerns the dimensions of the pars venosa, has been attributed to transverse sinus dominance. We found no statistically significant difference in the jugular foramen volume (right, left, or total) between the IIH and control groups. A trend toward a larger right jugular foramen compared with the left was observed in both groups, consistent with normal anatomical variations reported in the literature. However, this right–left asymmetry between the two groups did not represent a statistically significant difference. We assessed the total volume of the jugular foramen, whereas the relative contributions of the pars nervosa and pars venosa may differ. Such compartment-specific differences could theoretically influence venous outflow by altering local flow dynamics rather than by absolute bony size alone. The inability to calculate both compartments separately may therefore be considered as a study limitation.
Although studies focusing specifically on jugular foramen volume in IIH are scarce, several investigations have highlighted the importance of venous outflow pathways in the disease’s pathophysiology. Previous work has demonstrated that transverse sinus stenosis, internal jugular vein narrowing, or extrinsic jugular vein compression may significantly contribute to impaired venous drainage and elevated intracranial pressure. 11 For example, in 2022, Wang et al. emphasized that venous structural abnormalities are among the most reproducible imaging findings in patients with IIH. However, these studies primarily examined intracranial venous sinuses or cervical venous segments rather than osseous foraminal anatomy. 10
Importantly, these observations suggest that venous outflow impairment in IIH is predominantly functional or dynamic rather than solely related to static bony anatomy. Dynamic factors such as postural changes, venous compliance, and pressure gradients across venous segments may not be adequately captured by static CT-based volumetric measurements.
In contrast, studies focusing on jugular foramen anatomy such as the work by Rhoton (2000) and Li et al. (2021) have documented substantial interindividual variability in foramen shape and size without demonstrating a direct association with intracranial pressure disorders.8,9 Our findings align with these anatomical studies. Despite right–left asymmetry being common, such differences appear to reflect normal anatomical variation rather than pathological narrowing. The absence of significant volumetric differences between IIH and control groups in the present study further suggests that bony jugular foramen size alone is unlikely to play a primary role in the venous outflow disturbances associated with IIH.
Limitations
This study has certain important limitations that should be considered when interpreting the results. First, its retrospective design introduces the potential for selection bias, as cases were drawn from an imaging archive rather than a prospective cohort. Second, although volumetric measurements were performed using high-resolution CT and semi-automated software, small segmentation inaccuracies are possible, particularly in individuals with irregular bony contours or partial volume effects. Third, only total jugular foramen volume was evaluated; the pars venosa and pars nervosa compartments were not measured separately. Since the internal jugular vein traverses the pars venosa, compartment-specific evaluation might have provided more nuanced insights into venous outflow dynamics. Additionally, the sample size, while adequate for detecting moderate differences, may be underpowered to identify subtle anatomical variations. Finally, IIH is a multifactorial disorder, and bony foraminal anatomy represents only one component of a complex venous and CSF regulatory system.
Taken together, the findings of this study indicate that jugular foramen volume does not differ significantly between individuals with IIH and healthy controls. These results suggest that bony foraminal morphology is unlikely to be a major contributing factor to impaired venous outflow in IIH. Future studies incorporating compartment-specific analyses and dynamic venous imaging techniques may help clarify whether functional venous abnormalities play a secondary role in the disease’s pathogenesis.
Footnotes
Acknowledgments
We are grateful to our patients and their families for inspiring us.
Author contributions
Conception: BE and HŞ; design: HŞ and HK; supervision: BE and MK; materials: MB and BE; data collection and/or processing: BE, HŞ, MB, and HK: analysis and/or interpretation: MB and MK; literature: HŞ and HK; review: BE, HŞ, HK, and MB; writing: BE; critical review: MK and HŞ
Consent for publication
Due to the retrospective nature of the study and the use of fully anonymized imaging and clinical data, individual written informed consent was not required. All patient data were deidentified prior to analysis, and no identifiable personal information (e.g. name, date of birth, and appointment details) is presented in the manuscript.
All authors have read and approved the final version of the manuscript and consented to its publication in the Journal of International Medical Research.
Data availability statement
All data generated or analyzed during this study are available from the corresponding author upon reasonable request.
Declaration of conflicting interests
No financial or nonfinancial benefits have been received or will be received from any party related directly or indirectly to the subject of this article. The authors declare that they have no relevant conflict of interest.
Ethical approval
All procedures involving human participants were conducted in accordance with the ethical standards of the institutional and/or national research committee and Declaration of Helsinki (1975, revised in 2024) or comparable ethical standards. This study was approved by the Non-Interventional Research Ethics Committee of Fırat University (Document Date and Number: 01.11.2024–28577).
Funding
The authors declared that this study has received no financial support.
Informed consent
Not required.
