Effect of diverticulum entrance diameter on sigmoid sinus hemodynamics: a CFD and PIV experimental validation study.

Geometric changes in the sigmoid sinus diverticulum (SSD) can alter its hemodynamic - a primary factor contributing to pulsatile tinnitus (PT). However, not all SSD cases lead to clinical PT symptoms. This study aims to investigate the influence of the diameter of the diverticulum (EDD) on the hemodynamics of the sigmoid sinus in PT. We reconstructed CTA images from 26 PT patients. A statistical analysis of EDD, depth, and diverticulum angle, was conducted across these cases. Based on the geometric characteristics obtained, we established seven idealized models with varying EDDs and performed computational fluid dynamics simulations. Mass flow was set at the inlet, and the outlet was assigned zero pressure. We conducted Particle Image Velocimetry experiments verification. The SSD geometric models were 3D-printed using UV-curable resin material. As the EDD decreased from 11 mm to 9.65 mm, wall pressure within the SSD increased. However, further decreases in EDD from 9.65 mm to 8.3 mm resulted in a reduction in wall pressure (case1: 123.597 Pa vs. case2: 121.325 Pa vs. case3: 128.823 Pa vs. case4: 140.814 Pa vs. case5: 124.172 Pa vs. case6: 120.559 Pa vs. case7: 124.138 Pa). The pressure within the diverticulum first increased and then decreased, with the most intense vortex blood flow observed at an EDD of 9.65 mm. The EDD is a key factor influencing hemodynamic changes within the sigmoid sinus. The intermediate EDD induce more significant blood flow disturbances. This study provides theoretical insights for PT diagnosis and diverticulum morphology assessment.