Hemodynamic study on the different therapeutic effects of SSWD resurfacing surgery on patients with pulsatile tinnitus.

Sigmoid sinus wall anomalies (SSWA) are a common pathophysiology of pulsatile tinnitus (PT) and usually treated by sigmoid sinus wall dehiscence (SSWD) resurfacing surgery. However, symptoms of tinnitus remain unrelieved after surgery in some patients with PT, and even new tinnitus appears. The cause of the difference in therapeutic effects is unclear. In this study, eight patient-specific SSWA geometric models were reconstructed on the basis of computed tomography angiography, including four cases of postoperative rehabilitation (group 1, 1-4 cases) and four cases of non-rehabilitation (group 2, 5-8 cases). Transient-state computational fluid dynamics (CFD) was performed to clarify the SS blood flow pattern and hemodynamic states. The wall pressure distribution on SSWA area, pressure difference, and flow pattern in SS were calculated to evaluate the hemodynamic changes of rehabilitation and non-rehabilitation patients before and after surgery. The difference of hemodynamics between these patients was statistically analyzed. The accuracy of CFD simulation was evaluated by cross validating the numerical and particle image velocimetry experimental results. Results showed that the SSWA area in patients with PT was loaded with high pressure. No difference was found in the hemodynamic characteristics between the two groups pre- and postoperation. When the average pressure (P) and time-average P (TAP) on the SSWA area were studied, the TAP difference pre- and postoperation between the two groups was found significant (p = 0.0021). The TAP difference had a negative change in postoperative rehabilitation patients (case 1, -44.49 Pa vs. case 2, -15.85 Pa vs. case 3, -25.88 Pa vs. case 4, -16.58 Pa). The postoperative TAP of non-rehabilitation patients was higher than the preoperative one (case 5, 24.70 Pa vs. case 6, 28.56 Pa vs. case 7, 5.81 Pa vs. case 8, 13.04 Pa). The velocity streamlines in the SS with rehabilitation became smoother and more regular than that without rehabilitation. By contrast, the velocity streamlines in SS without rehabilitation showed increased twisting and curling. No difference was found in time-average volume-averaged vorticity (TAVV) between the two groups. Therefore, the high pressure of the vessel wall on SSWA area was one of the causes of PT. The variation of SSWA wall pressure difference before and after PT was the cause of the difference in therapeutic effects after SSWD resurfacing surgery. In patients with SSWA, disordered blood flow in SS was another cause of PT. SSWD repair may relieve tinnitus to some extent, but blood flow disorders may still arise.