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Pulsatile Tinnitus (PT) is a pulse-synchronous sound heard in the absence of an external source. PT is often related to abnormal flow in vascular structures near the cochlea. One vascular territory implicated in PT is the internal jugular vein (IJV). Using computational fluid dynamics (CFD) based on patient-specific Magnetic Resonance Imaging (MRI), we investigated the flow within the IJV of seven subjects, four symptomatic and three asymptomatic of PT. We found that there were two extreme anatomic types classified by the shape and position of the jugular bulbs: elevated and rounded. PT patients had elevated jugular bulbs that led to a distinctive helical flow pattern within the proximal internal jugular vein. Asymptomatic subjects generally had rounded jugular bulbs that neatly redirected flow from the sigmoid sinus directly into the jugular vein. These two flow patterns were quantified by calculating the length-averaged streamline curvature of the flow within the proximal jugular vein: 130.3 ± 8.1 m-1 for geometries with rounded bulbs, 260.7 ± 29.4 m-1 for those with elevated bulbs (P < 0.005). Our results suggest that variations in the jugular bulb geometry lead to distinct flow patterns that are linked to PT, but further investigation is needed to determine if the vortex pattern is causal to sound generation.

Background and Purpose Case reports demonstrate coiling of sigmoid sinus diverticulum (SSD) can treat pulsatile tinnitus (PT). We hypothesize MR 4D Flow (4DF) and computational fluid dynamics (CFD) will reveal distinct blood flow patterns in the venous outflow tract in these patients. Materials and Methods Patients with PT of suspected venous etiology underwent MRI at 3T, using venous phase contrast-enhanced MR angiography (CE-MRA), 4DF, and 2D phase contrast. The CE-MRA contours were evaluated to determine the presence and extent of SSD. CFD analysis was performed using the 4DF inlet flow and the lumenal contours from CE-MRA as boundary conditions. In addition, CFD was also performed for the expected post-treatment conditions by smoothing the venous geometry to exclude the SSD from the anatomic boundary conditions. Streamlines were generated from the 4DF and CFD velocity maps and flow patterns were examined for the presence of rotational components. Results Twenty-five patients with PT of suspected venous etiology and 10 control subjects were enrolled. Five (20%) of the symptomatic subjects had SSD, all associated with an upstream stenosis. In each of these cases, but none of the controls, a stenosis-related flow-jet was directed toward the opening of the SSD with rotational flow patterns in the SSD and parent sigmoid sinus on both 4DF and CFD that were absent in controls. Conclusion Consistent patterns of blood flow can be visualized in SSD and the parent sinus using 4DF and CFD. Strong components of rotational blood flow were seen in subjects with SSD that were absent in controls.

4D flow MRI with extended motion-encoding enables quantification of both the velocity and the Reynolds stress tensor. The additional information provided by this method improves the assessment of pressure gradients across a stenosis in the presence of turbulence. Unlike conventional methods, which are only valid if the flow is laminar, the proposed method is valid for both laminar and disturbed flow, a common presentation in diseased vessels. Magn Reson Med 79:1962-1971, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

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