An in vitro experimental study on the synergistic pathogenicity analysis of pulsatile tinnitus involving venous flow velocity, sigmoid sinus wall dehiscence and sinus malformation.

Pulsatile tinnitus (PT) is synchronous with patients' heartbeat, with various reported intracranial etiologies. Sigmoid sinus wall dehiscence (SSWD), sinus malformation and high venous flow velocity were common marks of PT and were generally treated as independent etiology in clinic, but their coupling effect remains unclear. This study aimed to investigate the synergistic pathogenicity of these etiologies. The generation and propagation of venous sound was simulated by in vitro experiment. The entity models of sinus vessel, sinus wall and temporal bone cavity were 3D-printed using resin based on CT imaging. Pulsatile venous flow was generated through sinus lumen, with five velocity levels. Venous sound was collected and analyzed. It was found that pressure and pulsation of venous sound were determined by the coupling of three etiology conditions. Low velocity would not induce pulsatile sound anyway. Sub-high or higher velocity induced mild pulsatile sound coupling with normal sinus and wall. Medium or higher velocity induced moderate pulsatile sound coupling with SSWD and normal sinus. Sub-low or higher velocity induced moderate or severe pulsatile sound coupling with SSWD and sinus malformation. In conclusion, PT diagnosis should include the three investigated etiologies due to their contribution to amplifying venous sound. Among the three etiologies, SSWD exhibits the highest pathogenicity, while high venous flow velocity may reduce the effectiveness of SS wall reconstruction, and sinus malformation may exacerbate the intensity of tinnitus induced by SSWD.