Multi-position head-and-neck rotational CT venography evaluation of dynamic changes in internal jugular vein compression in patients with an elongated styloid process

Introduction

We present an instructive case of a 73-year-old woman with a history of right parasagittal meningioma. The patient was placed in the left lateral decubitus position with the neck rotated approximately 30° to the left. The surgery was performed successfully; however, postoperatively, the patient developed recurrent intracranial hemorrhage, intracranial hypertension, severe brain injury, deep coma, and absence of spontaneous respiration. Despite multidisciplinary consultation and corresponding therapeutic interventions, her condition could not be reversed, and she ultimately died of respiratory and circulatory failure.

A multidisciplinary case review involving senior neurosurgeons concluded that the cause of the postoperative recurrent hemorrhage extended beyond the patient’s advanced age and coagulopathy, and was primarily driven by intracranial venous outflow obstruction. The obstruction was attributed to bilateral elongated styloid processes (ESPs) [left: 48.5 mm; right: 33.5 mm; normal range: 20–30 mm (1)]. This anatomical variation likely caused chronic compression of the internal jugular veins (IJVs), establishing a pre-existing state of impaired venous outflow.

Intraoperatively, the sustained left neck rotation compressed the left IJV, while procedure-related edema at the right sigmoid sinus concurrently impaired drainage on the contralateral side. Together, these factors led to severe bilateral jugular outflow obstruction throughout the operation, critically impeding cerebral venous return, culminating in irreversible intracranial hypertension.

Similar findings have been reported previously. Gooding et al. (2) conducted studies on infant monkeys and cadaver specimens, and concluded that when one IJV is obstructed due to resection, ligation, or cannulation, contralateral neck rotation may compress the opposite IJV, leading to severe complications. Brinjikji et al. (3) described a case in which a patient with unilateral IJV hypoplasia developed significant symptoms due to contralateral IJV compression during neck rotation, with marked symptom relief following surgery. These studies emphasize the critical importance of assessing contralateral IJV patency after neck rotation in patients undergoing intracranial procedures that require such positioning, particularly when surgical maneuvers may compromise venous return on one side.

IJV compression by the styloid process (SP) and C1 transverse process (TP) in the neutral neck position has been documented (4-6); however, it remains unclear whether such compression persists or changes dynamically during neck rotation. The complexity of this issue arises from two factors. First, the anatomical course of the IJV is intricate (5,7-11); aside from bony structures, adjacent arteries, muscles, and even certain organs (e.g., an enlarged thyroid or submandibular gland) may contribute to compression. Second, clinical symptoms often do not correlate fully with imaging findings. An ESP does not invariably lead to symptoms (12,13), partly because IJV compression usually arises from the combined interaction of the ESP and surrounding structures (14), as well as compensatory contralateral drainage. Consequently, some patients with evident physical compression may remain asymptomatic, whereas others with anatomically “normal” structures may develop symptoms during neck rotation due to dynamic compression from adjacent tissues (3). Therefore, further investigation of the dynamic behavior of the IJV during neck rotation is warranted.

This study sought to elucidate dynamic changes in IJV compression in patients with an ESP using multi-position head-and-neck rotational computed tomographic venography (CTV), and to preliminarily investigate the key anatomical structures responsible for venous compression, thereby providing imaging and anatomical evidence to support individualized treatment planning. We present this article in accordance with the STROBE reporting checklist (available at https://qims.amegroups.com/article/view/10.21037/qims-2026-1-0376/rc).

Methods

Clinical data

Images from 42 consecutive head-and-neck rotational CTV examinations performed between August 2024 and December 2025 in patients with an ESP were retrospectively reviewed. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. This retrospective study was approved by the Ethics Committee of The First Affiliated Hospital of Chongqing Medical University (No. 2026-0126-01), which waived the requirement for informed consent due to the retrospective nature of the study and the use of de-identified patient data.

The inclusion criteria were as follows: (I) clinical symptoms suggestive of IJV compression due to an ESP; and (II) successful completion of head-and-neck rotational CTV with excellent image quality. The exclusion criteria were as follows: (I) a history of cervical surgery altering the peri‑internal jugular venous anatomy; and/or (II) the presence of metallic implants in the neck region, such as spinal internal fixation devices following vertebral surgery or cervical vascular stents.

A total of 42 patients were included in this study. Positive findings were defined as severe IJV compression (a short‑axis diameter ratio and a stenosis area ratio, both of which exceeded 80% compared with adjacent normal segments) or complete IJV interruption. Among the examined patients, 30 were positive for severe IJV compression or complete IJV interruption, yielding a positivity rate of 71.43%. The major clinical symptoms documented included headache (7 cases), dizziness (13 cases), tinnitus (5 cases), head noise (4 cases), and neck pain (1 case).

The mean age of the patients with positive results was 52.7±11.3 years, and 17 were male (mean age 51.2±11 years) and 13 were female (mean age 54.5±11.9 years). The data collected for each patient included age, sex, SP type (continuous or segmented), and the degree of cervical collateral circulation compensation, which was classified into four grades: none, mild, moderate, and severe.

Instruments and methods

Imaging was performed using a 512‑slice computed tomography (CT) scanner (NeuViz Epoch, Neusoft Medical Systems Co., Ltd., Shenyang, China) with a 16‑cm wide detector. Contrast agent and saline were administered via the median cubital vein using a power injector (Medrad Stellant, Bayer Medical Care Inc., Indianola, Pennsylvania, USA). The imaging protocol comprised two scans.

First scan protocol

Computed tomographic angiography (CTA) and CTV were performed with the patient in the supine position and the head/neck extended. A cushion was placed under the neck to maintain an extended position. The scan range extended from the inferior margin of the aortic arch to the vertex. A non‑contrast scan was acquired first, followed by a CTA scan. Bolus tracking was performed at the level of the aortic arch, with a region of interest placed over the aortic arch and a trigger threshold set at 150 Hounsfield units (HU). Once the threshold was reached, a CTA scan was initiated. After a 6‑second delay, the CTV scan was performed. For patients with tumors, an additional delayed phase was acquired over the lesion region. The scanning parameters were as follows: tube voltage: 100 kV; tube current: 450 mA; rotation speed: 0.374 s; pitch: 0.6; collimation: 128 ×0.625 mm; slice thickness: 5 mm; slice interval: 5 mm; filter: H20LD; image enhancement factor: 1.0. Contrast agent administration: Both contrast agent and saline were injected intravenously via the median cubital vein using a high-pressure injector (Medrad Stellant). For the first-phase scan, the flow rate and total volume of the contrast agent and saline were calculated using the P3T system based on the patient’s body weight.

Second scan protocol (perfusion sequence)

The second scan was performed using a perfusion sequence with the neck in flexion, left rotation, and right rotation. An inclined pillow was used to maintain neck flexion, and patients were instructed to practice left and right neck rotations before the examination. During scanning, patients were first asked to maintain neck flexion, and then to rotate their neck according to the technician’s instructions. The scanning range extended from the supraclavicular region to the sellar area, with monitoring at the C4 level of the carotid artery (CA). After contrast injection, continuous scanning was performed during the peak enhancement phase of the internal CA and jugular vein using a wide-area detector without table movement or cradle-like advancement until the patient completed three positions: maximum neck flexion, maximum left neck rotation, and maximum right neck rotation. To minimize motion artifacts, three sets of images were acquired for each position, resulting in a total of nine image sets. The scanning parameters were as follows: tube voltage: 70 kV; tube current: 464 mA; rotation speed: 0.259 s; pitch: 0.4; collimation: 496 ×0.625 mm; slice thickness: 5 mm; slice interval: 5 mm; filter: H20LD; image enhancement factor: 1.0. Contrast agent administration: Both contrast agent and saline were administered at a flow rate of 2 mL/s, with a volume of 60 mL each.

Imaging parameter measurement and analysis

Measurement parameters

Based on the images acquired from the four positional scans, the slice showing the key peri‑IJV structures (bony, muscular, and vascular) with the closest proximity was selected for measurement (hereinafter referred to as the “XX-level”). For each structure, the following parameters were obtained: the shortest distance (in mm) between the structure and the IJV; the minimum diameter of the IJV (in mm) on the same slice; and the cross‑sectional area of the IJV (in mm²) on the same slice.

The evaluated structures included bony structures (C1 TP and SP), muscular structures [sternocleidomastoid muscle (SCM)], and vascular structures [CA and occipital artery (OA)]. Other cervical muscles (e.g., digastric muscle, longus colli, and longus capitis) were not consistently adjacent to the IJV, and were thus not included in the distance measurement; however, they were considered in the compression classification (see section “Classification of compressing structures” below). Additionally, the shortest distance between the SP and ipsilateral C1 TP was measured to assess their spatial relationship.

Classification of compressing structures

The level showing the narrowest or interrupted segment of the IJV was selected for analysis. Based on the number of adjacent structures directly compressing the IJV at this level, cases were categorized as follows: no compression, single-structure compression, dual-structure compression, or multi-structure compression (≥3 structures).

For the dual-structure compression group, the specific structural pairs were further classified as follows: bone-bone, bone-muscle, bone-vessel, muscle-vessel, muscle-muscle, and vessel-vessel.

The anatomical structures included in this classification were defined as follows: bony structures, including all cervical TPs and the SP; vascular structures, including the common CA, internal CA, external CA, and OA; and muscular structures, including the SCM, digastric muscle, longus colli, and longus capitis.

Statistical analysis

A structured database was created using specialized software (Microsoft Excel and SPSS version 26) to record all collected information and measurement parameters. All measurements were independently performed by two experienced radiologists, and the mean values were used for subsequent analyses.

Descriptive statistics were used to summarize patient characteristics, SP parameters (length and type), collateral circulation status, and all measured variables. Continuous variables with a normal distribution were expressed as mean ± standard deviation, while those with a non-normal distribution were presented as median (interquartile range).

Group comparisons were conducted as follows: age was analyzed using the independent samples t-test; SP type was compared using the chi-square test; SP length was assessed using the nonparametric rank-sum test; and collateral circulation patterns were evaluated using the Friedman test, followed by pairwise comparisons using the Wilcoxon signed-rank test with Bonferroni correction.

For comparisons across different neck positions (extension, flexion, left rotation, and right rotation), a one-way repeated-measures analysis of variance was applied for normally distributed data; otherwise, the Friedman test was used. Pairwise comparisons were subsequently performed using the Wilcoxon signed-rank test with Bonferroni correction.

A P value <0.05 was considered statistically significant.

Results

No statistically significant differences were observed among the 30 patients with positive findings in terms of sex, age, SP type, or SP length between the left and right sides (Table 1).

At the CA level, the distance between the ipsilateral IJV and the CA during neck rotation to the same side was significantly smaller than that in the other three positions. Moreover, during left and right neck rotations, the diameter and cross-sectional area of the ipsilateral IJV at this level were the smallest among all the positions. At the TP and SP levels, the diameter and cross-sectional area of the ipsilateral IJV were the largest during contralateral neck rotation. At the OA level, the diameter of the left IJV was smallest during flexion. In terms of the cross-sectional area, the left IJV was smaller during flexion than during left rotation, and the right IJV was smaller during flexion than during right rotation. At the SCM level, the diameter and cross-sectional area of the ipsilateral IJV were smallest during neck rotation to the same side. Additionally, among the four positions, the distance between the TP and SP was shortest on both sides during neck flexion. All the above comparisons were statistically significant. The detailed measurement data are presented in Tables 2,3.

During ipsilateral neck rotation, a significant increase in the degree of collateral circulation around the IJV was observed (P<0.05). Specifically, moderate collateral circulation (53.3%) was predominantly observed around the left IJV during left rotation, whereas moderate-to-severe collateral circulation (33.3% and 23.3%) was more frequently observed around the right IJV during right rotation. The detailed distributions are presented in Tables 4,5.

Among the 30 positive patients, in the extension position, the positive rate of the left IJV was 3/30 and that of the right IJV was 1/30; in the flexion position, the positive rate of the left IJV was 6/30 and that of the right IJV was 4/30; in the left rotation position, the positive rate of the left IJV was 30/30 and that of the right IJV was 4/30; and in the right rotation position, the positive rate of the left IJV was 4/30 and that of the right IJV was 28/30.

In these 30 patients, 60 IJVs were assessed in four positions (240 observations). Of these 240 observations, 80 (33.3%) exhibited severe stenosis or interruption. Dual-structure compression was the most common pattern, with the most frequently observed subtypes being muscle-muscle compression (27/80, 33.75%), muscle-vessel compression (23/80, 28.75%), and bone-bone compression (11/80, 13.75%), in descending order of frequency. Detailed results are summarized in Table 6.

The changes in the IJVs in the four positions are shown in Figures 1 and 2.

Figure 1 Head-and-neck rotational CTV of a 41-year-old male in extension (A), flexion (B), left rotation (C), and right rotation (D). (A) Extension view shows the labeled structures. White arrow, IJV (patent); green arrow, styloid process; red arrows, interrupted IJV. CTV, computed tomographic venography; IJV, internal jugular vein.

Figure 2 Head-and-neck rotational CTV of a 67-year-old male. (A-C) Extension; (D-F) flexion; (G,H) left rotation; (I,J) right rotation. (A,D) Anterior views; (B,E) posterior views; (C,F) axial views. White arrow, patent internal jugular vein; red arrows, stenosed/interrupted IJV; green arrow, styloid process; yellow arrows, collateral circulation; purple arrows, internal carotid artery; blue arrow, digastric muscle; black arrow, sternocleidomastoid muscle. CTV, computed tomographic venography; IJV, internal jugular vein.

Discussion

This study analyzed the CTV images of patients with an ESP in four head-and-neck positions (extension, flexion, left rotation, and right rotation). Our findings demonstrated that neck rotation significantly increased the incidence of ipsilateral IJV compression or interruption in these patients. This observation provides objective imaging evidence that may help explain the association between specific head movements (e.g., positional dizziness and tinnitus) and potential venous compression, although a direct causal relationship has yet to be established, particularly regarding the temporal correlation. More importantly, it provides critical evidence for standardizing patients’ daily activities and optimizing perioperative assessment protocols.

Currently, arterial stenosis evaluation is typically based on the ratio of the minimum luminal diameter to the original long diameter (15). In contrast to arterial assessment, venous stenosis evaluation currently lacks a unified standard. Different diagnostic methods frequently yield inconsistent conclusions (16). Further, due to the lower intraluminal pressure and relative paucity of smooth muscle and elastic fibers (17), veins are more prone to deformation (e.g., changing from a circular to an elliptical or irregular shape) rather than simple luminal narrowing when subjected to external compression. Therefore, venous assessment requires its own evaluation standard. While some studies have applied arterial stenosis criteria to venous evaluation (18), the primary aim of this study was not to quantify a specific stenosis rate but to dynamically assess variations in IJV compression as a function of posture across four defined positions. Reliance on short-axis diameter measurements alone is insufficient for this purpose. To address this limitation, we introduced a multi-parameter assessment protocol. By comparing CTV images across the four postures, we measured the following parameters (19): the shortest distances between the IJV and five key adjacent anatomical structures (the TP, SP, CA, OA, and SCM), as well as the venous short-axis diameter and cross-sectional area at the same level. This comprehensive approach allows for a more accurate dynamic assessment of the compression.

The results revealed that the IJV had a lower probability of severe compression in head extension and flexion, compared with left and right head rotation. Notably, statistically significant differences between extension and flexion were observed only at two locations: the IJV diameter on the plane of the left OA and the bilateral TP-SP distances. This suggests that the spatial relationship between the IJV and most surrounding structures remains relatively stable during head extension and flexion. Although the narrowing of the TP and SP distance reduces the anatomical space, the resulting compression may be mitigated by the anteroposterior displacement of the IJV.

In contrast, during left and right neck rotation, statistically significant differences were observed in both the diameter and cross-sectional area of the IJV at the levels of the CA, SCM, TP, and SP. However, the changes exhibited a dichotomous pattern: the short-axis diameter and cross-sectional area of the IJV were smallest at the levels of the CA and SCM but largest at the levels of the TP and SP. This pattern can be explained by the location of the primary stenosis. When the most severe narrowing occurs distally, the resulting impairment of venous outflow leads to compensatory dilatation in the more proximal segment of the IJV. Among the four postures, the variation in IJV parameters was minimal at the level of the OA and most pronounced at the level of the SCM. This indicates that the OA exerts the least positional influence on the IJV, while the SCM exerts the greatest positional influence. Lateral neck rotation induces scissor-like compression of the IJV through two concurrent movements: posterior displacement by contracting muscles (sternocleidomastoid and digastric) and anterolateral displacement of the adjacent deep structures (TP, CA, longus capitis, and colli), which converge from opposite directions.

Studies by Jayaraman and Geisbush et al. (4,5) indicate that, in a neutral head position, the upper segment of the IJV is primarily subjected to extrinsic compression by bony structures such as the SP, digastric muscle, or adjacent cervical TP. Although this was our initial hypothesis, it was not supported by the findings. While the subgroup sample size involving IJV compression in our study was limited, precluding precise statistical analysis, a preliminary assessment suggests that during lateral neck rotation, the greatest contribution to IJV compression arises from muscle-vessel and muscle-muscle interactions, with the SCM and CA exerting the most significant effects. This discrepancy can be primarily attributed to the difference in posture; the studies of Jayaraman and Geisbush et al. were conducted with patients in a relaxed, neutral position, in which bony compression predominates. Conversely, during active neck rotation, muscle contraction markedly increases compressive effects on the IJV, more readily producing the “scissor-like” compression mechanism observed in our study.

Research indicates that in the supine position, approximately 70–90% of cerebral venous blood drains through the IJVs (20-23). Acute, severe compression or occlusion can alter hemodynamics, elevate ipsilateral intracranial venous pressure, and promote the development of adjacent collateral circulation. According to Wang et al. (24), the presence of abnormal collateral vessels around the IJV is a key criterion for differentiating between acquired stenosis and congenital hypoplasia. We found that collateral circulation around the ipsilateral IJV was significantly augmented during neck rotation, indicating a consequent worsening of venous stenosis.

Based on this, patients with pre-existing severe IJV compression may theoretically be more susceptible to hemodynamic changes during neck rotation. From a surgical perspective, our imaging data raise the hypothesis that in patients with pre‑existing severe contralateral IJV compression, prolonged or high‑amplitude contralateral neck rotation during surgery may increase the risk of intracranial venous congestion. Accordingly, for cases requiring prolonged intraoperative neck rotation (e.g., unilateral skull base or cervical tumor resection), preoperative assessment using head-and-neck rotational CTV may be considered. This may help surgeons anticipate the potential risk of impaired venous outflow; however, the clinical value of such assessment requires further validation. Similarly, for procedures directly involving the IJVs (e.g., SP or TP resection), significant ipsilateral IJV compression observed on imaging may suggest chronic venous wall remodeling. Based on these imaging findings, surgeons may recognize an increased potential risk of venous fragility or adhesion, and accordingly ensure adequate hemostatic preparations. However, this association remains speculative at present, and is primarily based on anatomical observations.

Limitations

As a pilot study employing a recently introduced technique at a single center, the investigation was constrained by a limited sample size. Consequently, a precise statistical analysis of the relative contribution (i.e., subgroup weighting) of different anatomical structures to IJV compression could not be performed. Further studies with larger sample sizes are required to address this issue.

Future directions

To build on these findings, in our future research, we intend to: (I) expand the cohort to enable a multifactorial analysis of the causes of IJV compression; and (II) optimize the imaging protocol and explore three-dimensional reconstruction techniques for CTV. Our goal is to provide surgeons with high-quality visual references that offer a more intuitive understanding of anatomical relationships.

Conclusions

In patients with an ESP, left and right neck rotation significantly increases the incidence of ipsilateral IJV compression and even occlusion, as assessed by multi-position head-and-neck rotational CTV. This finding has important clinical implications, as it may guide modifications to patients’ daily habits and improve perioperative evaluation protocols.

Acknowledgments

We extend our gratitude to all the patients who participated in this study.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://qims.amegroups.com/article/view/10.21037/qims-2026-1-0376/rc

Data Sharing Statement: Available at https://qims.amegroups.com/article/view/10.21037/qims-2026-1-0376/dss

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2026-1-0376/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. This retrospective study was approved by the Ethics Committee of The First Affiliated Hospital of Chongqing Medical University (No. 2026-0126-01). Due to the retrospective nature of the study and the use of de-identified patient data, the requirement for informed consent was waived by the Ethics Committee.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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