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

Background: Neurosurgical procedures often require patients to maintain a rotated neck position for extended periods. This sustained posture may lead to internal jugular vein (IJV) compression, particularly in individuals with an elongated styloid process (ESP). This study aimed to elucidate the dynamic changes in IJV compression among patients with an ESP using multi-position head-and-neck rotational computed tomographic venography (CTV) imaging, and to preliminarily investigate the key anatomical structures responsible for venous compression, thereby providing imaging and anatomical evidence for individualized treatment planning. Methods: Images from 42 consecutive head-and-neck rotational CTV scans of patients with an ESP performed between August 2024 and December 2025 were reviewed. The slices for measurement were selected from images obtained in four positions (extension, flexion, left rotation, and right rotation) based on the criterion of the minimum distance between the IJV and its key adjacent structures (bony, muscular, and vascular). The shortest distance between these key structures and the IJV, as well as the minimum IJV diameter and cross-sectional area at the same slice level, was measured. The presence of collateral circulation in bilateral IJVs in each position was assessed, and a preliminary analysis of the compressive structures at the site of maximal narrowing of the IJV was performed. Results: A total of 42 patients were included in the study, of whom 30 were identified as positive for severe IJV compression or complete IJV interruption, yielding a positivity rate of 71.43%. At the carotid artery (CA) and sternocleidomastoid muscle (SCM) levels, the diameter and cross-sectional area of the ipsilateral IJV were significantly smaller during left and right neck rotation. In contrast, at the transverse process (TP) and styloid process (SP) levels, the ipsilateral IJV diameter and area were largest during left and right neck rotations. Further, among the four positions, flexion showed the shortest distance between the bilateral C1 TP and SP. During left and right neck rotation, the degree of collateral circulation around the ipsilateral IJV was significantly increased. All reported differences were statistically significant (P<0.05). A total of 240 vascular states were observed across the four positions, of which 80 (33.3%) exhibited severe stenosis or occlusion. Dual-structure compression was the predominant type, with the most common combinations being muscle-muscle compression (27/80, 33.75%), muscle-vessel compression (23/80, 28.75%), and bone-bone compression (11/80, 13.75%). 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.