Intraoperative Investigation of Vibration and Acoustic Characteristics of Venous Pulsatile Tinnitus Using Confocal Laser Displacement Sensor, Doppler Ultrasonography, and Piezoelectric Film Sensor: A Pilot Study

Abstract

The vibrations of a thinned sigmoid plate and exposed sinus vessel wall in patients with sigmoid sinus wall anomalies (SSWAs) have long been speculated to be a pivotal cause of venous pulsatile tinnitus (PT). This is the first in vivo study to investigate whether vibrations resulting from SSWAs induce PT using multiple sensor systems. A confocal laser displacement sensor system was intraoperatively deployed to gauge displacements of the focal anatomical structure in 12 subjects with venous PT with or without SSWAs. Doppler ultrasonography was performed to detect the blood flow and psychoacoustic characteristics of PT. Computational fluid dynamics (CFD) and piezoelectric sensors were deployed to assess the relationship between the vessel wall pressure and hemodynamics. The ultrasonographic examination showed that the PT pitch matched the blood flow sampled at the center of the sinus lumen in all subjects and that there was no statistical difference between the displacements of the sigmoid plate and vessel wall before separation, indicating that PT is strongly associated with flow-induced noise rather than vibration-induced noise. In addition, the quantitative water occlusion test can be potentially indicative for the surgical and mechanistic study of PT.1. # indicates vascular displacement after the separation procedure (step 2). 2. ^ indicates the values obtained from CFD simulation.

Hydroacoustic Sonification and Flow Pattern Investigation of Venous Pulsatile Tinnitus Using MEMS Hydrophone Sensing and Dye Flow Visualization Techniques: Pilot 3D Printing, Computational Fluid Dynamics, and Psychoacoustic Study

“…Venous PT has been clinically theorized to transmit via airand bone-conduction pathways. (3,9,10) According to our previous in vivo measurements using displacement sensors, the motion of the sigmoid sinus vessel wall seems unlikely the major cause of PT. (10) This raises a postulation that the airtight condition of the mastoid cavity and/or the defective bony plate may facilitate the fluid-borne sound transmission to the inner ear.…”

“…(3,9,10) According to our previous in vivo measurements using displacement sensors, the motion of the sigmoid sinus vessel wall seems unlikely the major cause of PT. (10) This raises a postulation that the airtight condition of the mastoid cavity and/or the defective bony plate may facilitate the fluid-borne sound transmission to the inner ear. In addition to the fluid-borne sound alone, the hydrodynamic pressure may also contribute to PT sound transmission, typically via the bone-conduction route.…”

“…For some patients, PT persists after mastoidectomy under local anesthesia, although the PT of a few patients disappears once the mastoid is cut open. (3,8,10) This clearly indicates that the airtight environment plays an important role in the transmission of PT, and when the mastoid air cells are eliminated, it is likely that the flow sound energy dissipates to the open air, rendering PT inaudible. A positive response to the water occlusion test or the ear-cover test (adding pressure to the middle ear) may suggest the compromised integrity of the sigmoid sinus bony plate for patients with SSWA.…”

“…(7) However, the bone-conduction transmission route has recently been indicated because low-frequency sound travels more efficiently through solid objects such as the temporal bone. (3,10) Since the evaluation of the absolute amplitude of PT and the identification of transmission pathways of PT can be challenging, extrinsic sensing and computational techniques are crucial to understand the hydroacoustic characteristics of PT.…”

“…In real clinical settings, not only do the shape and flow characteristics in the transverse-sigmoid sinus vary vastly but also the human anatomical structures are exquisitely sophisticated. (3,10) To that end, a uniformly given boundary condition can only provide a general indication for studies of the computational flow field.…”