Purpose Pulsatile tinnitus (PT) is a debilitating condition that can be caused by abnormal blood flow in venous vasculature near the cochlea1. Often times PT is very difficult to diagnose reliably with diagnosis rates typically hovering around 50% and requiring multiple advanced imaging procedures including diagnostic cerebral angiography2. A tool that could objectively mimic a PT patient’s hearing experience would allow physicians to reliably diagnose the cause of this difficult symptom.
Materials and Methods We developed a prototype of the ‘Phonocatheter’, a 6 Fr catheter that can measure and record PT sounds as well as replay them in real time. The Phonocatheter consists of an embedded microphone at its distal end to record intravascular sounds and relay them to a microcontroller (Arduino Mega 2560 Rev3) based custom data acquisition interface. Two benchtop PT flow models3 that represent a PT patient’s transverse sinus (TS) anatomy before and after lumbar puncture (LP) were created and used to test the Phonocatheter. Glycerol-water mixture was pumped through these models to mimic blood flow at a mean flow rate of 7.4 cc/s. The Phonocatheter was inserted through a 9 Fr access port and was navigated into the TS stenosis region (figure 1A). A handsfree Bluetooth compatible electronic stethoscope was placed externally over the same TS region to record PT transluminally and validate the sound measurements recorded by Phonocatheter (n=10). The sound measurements acquired by Phonocatheter and stethoscope were saved in .wav file format and were exported to MATLAB for comparative analysis. Variation in peak-to-rms sound amplitude values from the TS in pre-LP and post-LP models was calculated. Wilcoxon rank sum test was used to statistically determine the differences in sound measurements between the two patient-specific models for each sensor.
Results Both the Phonocatheter and stethoscope were able to record transluminal and intravascular sounds generated from stenosis respectively. The Phonocather was in good agreement with the stethoscope demonstrating that the peak-to-rms (mean ± standard deviation) sound amplitude was significantly louder (p<0.0001) in the TS stenosis region in pre-lumbar puncture model (Stethoscope: 9.03 ± 1.61; Phonocatheter: 6.62 ± 1.55) compared to the TS region in post-lumbar puncture model (Stethoscope: 4.20 ± 0.86; Phonocatheter: 3.62 ± 0.88) (figures 1B and 1C).
Conclusion We have developed a prototype of microphone enabled catheter that can measure sound in patient-specific PT flow models, and potentially measure sounds quantitively in PT patients.
Disclosures M. Amans: 1; C; NIH R01 HL149124-01A1. K. Valluru: None. S. Kondapavulur: None. B. Kilbride: None. H. Haraldsson: None. W. Smith: None. K. Meisel: None. D. Saloner: None.
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