MR Venous Flow in Sigmoid Sinus Diverticulum

Venous sinus diverticulum in patients with pulsatile tinnitus: An acquired lesion

BACKGROUND

The etiopathogenesis of venous sinus diverticulum is controversial. Conflicting evidence has been published suggesting that venous sinus diverticulum is either a congenital or acquired lesion.

METHODS

This is a case report of a single individual followed for 17 years within a single healthcare system.

RESULTS

An early middle-aged woman presented with unilateral pulsatile tinnitus, vertigo, and decreased hearing. Initial imaging was unrevealing. Interval imaging after 13 years revealed the development of an ipsilateral venous sinus diverticulum. The patient was treated via endovascular stenting and coiling of the lesion with complete resolution of symptoms.

CONCLUSIONS

We demonstrate that a venous sinus diverticulum in a patient with pulsatile tinnitus is an acquired lesion. Further research is warranted to better elucidate the precise etiology and pathophysiology of acquired venous sinus diverticulum, potentially guiding management strategies.

Interactive effect of hemodynamics in transverse sigmoid sinus and bone morphology on venous pulsatile tinnitus: a four-dimensional (4D) flow magnetic resonance imaging (MRI) study

Background

The hemodynamic pathogenesis of venous pulsatile tinnitus (VPT) is still unclear. This study aimed to explore the mechanism of bone morphology and hemodynamic changes in transverse sigmoid sinus (TSS) on VPT patients.

Methods

49 patients with unilateral VPT, 26 patients with subjective tinnitus and 36 healthy controls were included in this retrospective clinical trial. Four-dimensional (4D) flow magnetic resonance imaging (MRI) was used to evaluate the hemodynamics of the TSS. High-resolution computed tomography was used to assess the perivenous bone structures. All images were independently assessed for each participant by two trained neuroradiologists. Kolmogorov-Smirnov test was used to determine the normal distribution of the data. Chi-square test and nonparametric test were used to compare classified or continuous variables. Stepwise linear regression and mediation effect analysis was used to explore the relationship between bone dehiscence (BD), hemodynamic factors and VPT symptoms.

Results

Peak velocity (P=0.001) and maximum energy loss (P=0.041) in VPT group were risk factors for the severity of tinnitus. Energy loss [indirect effect =0.692, P<0.005, 95% confidence interval (CI): 0.201-1.377] and peak velocity (indirect effect =0.899, P<0.005, 95% CI: 0.406-1.582) demonstrated the complete mediation effect between the BD and VPT. BD showed a complete mediation effect between the wall shear stress (WSS) and VPT (indirect effect =15.181, P<0.005, 95% CI: 3.448-35.493).

Conclusions

Cross-talk between the hemodynamic changes of TSS and BD can regulate the VPT symptoms. This type of analysis might be helpful in establishing the possible occurrence and development mechanism of the hemodynamics and bone morphology of the VPT.

Flow Analysis of Central Venous Outflow Tract: A New Approach to Understanding Pulse-Synchronous Tinnitus

OBJECTIVE

Pulse-synchronous tinnitus (PST) has been linked to multiple anatomical variants of the central venous outflow tract (CVOT) including sigmoid sinus (SS) dehiscence and diverticulum. This study investigates flow turbulence, pressure, and wall shear stress along the CVOT and proposes a mechanism that results in SS dehiscence and PST.

STUDY DESIGN

Case series.

SETTING

Tertiary Academic Center.

METHODS

Venous models were reconstructed from computed tomography scans of 3 patients with unilateral PST. Two models for each patient are obtained: a symptomatic and contralateral asymptomatic side. A turbulent model-enabled commercial flow solver was used to simulate the pulsatile blood flow over the cardiac cycle through the models. Fluid flow through the transverse and SS junction was analyzed to observe the velocity, pressure, turbulent kinetic energy (TKE), and shear stress over a simulated cardiac cycle.

RESULTS

Fluid flow on the symptomatic side showed increased vorticity in the presence of an SS diverticulum. Higher TKE with periodicity following the cardiac cycle was observed on the symptomatic side, and a sharp increase was observed if SS diverticulum was present. Shear stress was highest near the narrowest segments of the vessel. Pressure was observed to be lower on the symptomatic side at the transverse-SS junction for all 3 patients.

CONCLUSION

Computational fluid dynamics modeling of blood flow through the CVOT in PST suggests that low pressure may be the cause of dehiscence, and tinnitus may result from periodic increases in TKE.

Endovascular vs surgical treatment of sigmoid sinus diverticulum causing pulsatile tinnitus: A systematic review

INTRODUCTION

Sigmoid sinus diverticulum (SSD) has been increasingly reported as a cause of pulsatile tinnitus (PT). While both endovascular and surgical treatments have been used, there is a lack of consensus on the treatment modality to treat SSD. We conducted a systematic review of the available literature to compare the clinical outcomes and safety of endovascular versus surgical approaches for treating SSD.

METHODS

A systematic review was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses to identify studies encompassing the management of SSD. Studies reporting the clinical outcomes and safety of endovascular or surgical treatments for SSD between January 2000 and January 2023 were included. Results were characterized using descriptive statistics.

RESULTS

Endovascular treatment (EVT) was reported by 17 articles, yielding 26 patients with 27 diverticula. Surgical treatment was reported by 20 articles, yielding 105 patients with 107 diverticula. EVT led to complete or near-complete resolution in all patients with SSD and PT. Complications occurred in 3.7% (1/27) with a return to baseline after 2 months. There were no permanent complications from EVT. Surgical treatment resulted in complete resolution in 77.6% (83/107) of cases, incomplete resolution in 11.2% (12/107), and no resolution in 11.2% (12/107). Significant complications occurred in 9.3% (10/107) of the surgical-treated patients.

CONCLUSION

EVT in patients with PT and venous diverticulum appears more effective and safer than surgical treatment, but large studies are lacking. Studies directly comparing endovascular and surgical treatment are needed.

Cerebral Sinus Hemodynamics in Adults Revealed by 4D Flow MRI

BACKGROUND

The hemodynamics of the cerebral sinuses play a vital role in understanding blood flow-related diseases, yet the hemodynamics of the cerebral sinuses in normal adults remains an unresolved issue.

PURPOSE

To evaluate hemodynamics in the cerebral sinus of adults using 4-dimensional flow MRI (4D Flow MRI).

STUDY TYPE

Cross-sectional.

POPULATION

Ninety-nine healthy volunteers (mean age, 42.88 ± 13.16 years old; females/males, 55/44).

FIELD STRENGTH/SEQUENCE

3 T/4D Flow MRI.

ASSESSMENT

The blood flow velocity, average blood flow rate (Q), and vortexes at the superior sagittal sinus (SSS), straight sinus (STS), transverse sinus, sigmoid sinus, and jugular bulb of each volunteer were evaluated by two independent neuroradiologists. The relationship between the total cerebral Q and sex and age was also assessed. Twelve volunteers underwent two scans within a month.

STATISTICAL TESTS

The intraclass correlation coefficient (ICC) evaluated the inter-observer agreement. Blood flow parameters among volunteers were compared by the independent-sample t-test or Mann-Whitney U test. The multiple linear regression equation was used to evaluate the relationship between total cerebral Q and age and sex. P < 0.05 indicated statistical significance.

RESULTS

The test-retest and interobserver reliability of average velocity and Q were moderate to high (ICC: 0.54-0.99). Cerebral sinus velocity varied by segment and cardiac cycle. The SSS's velocity and Q increased downstream and Q near torcular herophili was 3.5 times that through the STS. The total cerebral Q decreased by 0.06 mL/s per year (β = -0.06 ± 0.013) and was sex-independent within the group. Vortexes were found in 12.12%, 8.9%, and 59.8% of torcular herophili, transverse-sigmoid junction, and jugular bulb, respectively, and were related to higher upstream flow.

DATA CONCLUSION

Cerebral sinuses could be measured visually and quantitatively in vivo by 4D Flow MRI, providing a basis for future research on pulsating tinnitus, multiple sclerosis, and other related diseases.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 1.

Cerebral venous disorders: Diagnosis and endovascular management

The role of the venous circulation in neurological diseases has been underestimated. In this review, we present an overview of the intracranial venous anatomy, venous disorders of the central nervous system, and options for endovascular management. We discuss the role the venous circulation plays in various neurological diseases including cerebrospinal fluid (CSF) disorders (intracranial hypertension and intracranial hypotension), arteriovenous diseases, and pulsatile tinnitus. We also shed light on emergent cerebral venous interventions including transvenous brain-computer interface implantation, transvenous treatment of communicating hydrocephalus, and the endovascular treatment of CSF-venous disorders.

Causes and outcomes of revision surgery in subjects with pulsatile tinnitus

INTRODUCTION

Once the underlying pathology has been identified, pulsatile tinnitus (PT) can be treated successfully with surgical or interventional management. However, some patients experience residual or recurrent symptoms following initially successful surgical treatment, and require revision surgery or additional procedures. Here, we report a case series of patients who had undergone revision surgery or interventional treatment, and suggest possible ways of minimizing the need for revision.

METHODS

Between January 2014 and March 2023, a total of seven subjects underwent revision surgery or interventional treatment for persistent or recurrent PT after initial surgical treatment. Demographic data, reasons for revision, and changes in symptoms before and after revision were analyzed retrospectively. Temporal bone computed tomographic angiography images were reviewed to identify the causes and reasons for revision.

RESULTS

Of the seven subjects, six underwent sigmoid sinus (SS) resurfacing/reshaping due to ipsilateral diverticulum (Div) or dehiscence (Deh), and one underwent jugular bulb (JB) resurfacing due to a high-riding JB with bony Deh. Of the five subjects who underwent revision SS surgery due to recurrent SS-Div or SS-Deh, three showed marked resolution of PT, while the other two showed partial improvement of the symptoms. One subject who underwent revision JB resurfacing, and another who underwent additional transarterial embolization for a concurrent ipsilateral dural arteriovenous fistula, reported marked improvement of PT.

DISCUSSION

The possibility of recurrence should be taken into account when performing surgical intervention in patients with PT. The likelihood of recurrence can be minimized through a comprehensive evaluation to identify possible multiple etiologies, and through the use of durable materials and appropriate surgical methods.

Flow patterns in the venous sinus of pulsatile tinnitus patients with transverse sinus stenosis and underlying vortical flow as a causative factor

BACKGROUND

Transverse sinus stenosis (TSS) is commonly found in Pulsatile Tinnitus (PT) patients. Vortex flow is prominent in venous sinus with stenosis, and so it is important to determine the distribution and strength of the vortical flow to understand its influence on the occurrence of PT.

METHODS

In this study, by using computational fluid dynamics for hemodynamic analysis in patient-specific geometries based on Magnetic Resonance Imaging (MRI), we have investigated the blood flow within the venous sinus of 16 subjects with PT. We have employed both laminar and turbulent flow models for simulations, to obtain (i) streamlines of velocity distribution in the venous sinus, and (ii) pressure distributions of flow patterns in the venous sinus. Then, hemodynamic analysis in the venous sinus recirculation zone was carried out, to determine the flow patterns at the junction of transverse sinuses and sigmoid sinuses. Finally, we have proposed a new model for turbulence evaluation based on the regression analysis of anatomic and hemodynamics parameters.

RESULTS

Correlation analysis between the anatomical parameters and the hemodynamic parameters has shown that stenosis at the transverse sinus was the main factor in the local hemodynamics variation in the venous sinus of patients; in this context, it is shown that vorticity can be used as a prime indicator of the severity of the stenosis function. Our results have shown a significant correlation between the vorticity and the stenotic maximum velocity (SMV) (r = 0.282, p = 0.004). Then, a parameterized prediction model is proposed to determine the vorticity in terms of flow and anatomic variables, termed as the turbulence eddy prediction model (TEP model). Our result have shown that the TEP model is sensitive to the dominant flow distribution, with a high correlation to the flow-based vorticity (r = 0.809, p = 0.009).

CONCLUSIONS

The quantification of the vorticity (as both vorticity and MVV) in the downstream of TSS could be a marker for indication of turbulent energy at the transverse-sigmoid sinus, which could potentially serve as a hemodynamic marker for the functional assessment of the PT-related TSS.

Dynamic Volume Computed Tomography for Characterizing Pulsatile Tinnitus Caused by Sigmoid Sinus Diverticulum with Bone Defects: Clinical Implications

OBJECTIVE

The objective of this study is to investigate the diagnosis of dynamic volume computed tomography (CT) for pulsatile tinnitus caused by sigmoid sinus diverticulum (SSD) and bone defects.

METHODS

Data obtained by dynamic volume CT from 35 patients with SSD were retrospectively collected. Then the ear morphological parameters, including bone defect, transverse sinus stenosis, position of the jugular bulb, jugular bulb diverticulum, defect of the jugular bulb wall, gross venous sinus thrombosis and SSD, and blood perfusion parameters, including cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT), were evaluated and compared between the tinnitus side and the asymptomatic side of the ear.

RESULTS

The maximum diameters of the bone defects on the tinnitus side were greater than those on the asymptomatic side (Horizontal 6.36±2.35mm vs. 1.12±0.78mm; Longitudinal 4.87±1.25 vs. 0.88±0.06mm). Dynamic volume CT visually displayed the SSD herniated into the adjacent mastoid via the bone defect. Transverse sinus stenosis, high position of the jugular bulb, jugular bulb diverticulum, defect of the jugular bulb wall, and gross venous sinus thrombosis were present more frequently on the tinnitus side than on the asymptomatic side (P < 0.05). Moreover, CBF, CBV, and MTT were significantly greater on the tinnitus side than on the asymptomatic side (P < 0.05).

CONCLUSION

Dynamic volume CT examination is an effective method for the diagnosis of pulsatile tinnitus caused by SSD with bone defects.

Study on the correlation between hemodynamic status of the transverse sinus-sigmoid sinus and the clinical efficacy of sigmoid sinus wall reconstruction

BACKGROUND AND PURPOSE

For patients with pulsatile tinnitus who have both transverse sinus stenosis and sigmoid sinus wall anomalies, sigmoid sinus wall reconstruction surgery is the first-choice treatment when the trans-stenotic pressure gradient less than 10 mmHg. However, not all patients are cured by surgery. We hypothesized the abnormal hemodynamics caused by transverse sinus stenosis is associated with the clinical efficacy of surgery.

METHODS

Eight pulsatile tinnitus patients treated with surgery were retrospectively reviewed (4 rehabilitated, 4 nonrehabilitated). All patients had radiologically diagnosed transverse sinus stenosis and sigmoid sinus wall anomalies. A numerical simulation of the hemodynamics of the transverse sinus-sigmoid sinus was performed using computational fluid dynamics technology. Changes in the blood flow patterns before and after surgery were observed. The blood flow velocity at the stenosis, vorticity of blood flow in the sigmoid sinus and wall pressure distribution in the sigmoid sinus wall anomalies area were compared.

RESULTS

The blood flow velocity in the stenosis (preoperative P = 0.04, postoperative P = 0.004) and vorticity in the sigmoid sinus (preoperative P = 0.02, postoperative P = 0.007) pre- and post-surgery were significantly higher in the non-rehabilitation group than in the rehabilitation group. No significant difference was found in the wall pressure distribution in the sigmoid sinus wall anomalies area (preoperative P = 0.12, postoperative P = 0.24).

CONCLUSIONS

There is a clear correlation between the abnormal hemodynamic status caused by transverse sinus stenosis and the clinical efficacy of surgery. The blood flow velocity at the stenosis and vorticity of blood flow in the sigmoid sinus are factors influencing the clinical efficacy of surgery.

Retroauricular/Transcranial Color-Coded Doppler Ultrasound Approach in Junction With Ipsilateral Neck Compression on Real-Time Hydroacoustic Variation of Venous Pulsatile Tinnitus

Alterations in dural venous sinus hemodynamics have recently been suggested as the major contributing factors in venous pulsatile tinnitus (PT). Nevertheless, little is known about the association between real-time alterations in hemodynamics and the subjective perception of venous PT. This study aimed to investigate the hydroacoustic correlations among diverticular vortices, mainstream sinus flow, and PT using various Doppler ultrasound techniques. Nineteen venous PT patients with protrusive diverticulum were recruited. The mainstream sinus and diverticular hemodynamics before and after ipsilateral internal jugular vein (IJV) compression were investigated using an innovative retroauricular color-coded Doppler (RCCD) method to examine the correlation between the disappearance of PT and hemodynamic alterations. To reveal the hydroacoustic characteristics of disparate segments of venous return, a computational fluid dynamics (CFD) technique combined with the transcranial color-coded Doppler method was performed. When the ipsilateral IJV was compressed, PT disappeared, as the mean velocity of mainstream sinus flow and diverticular vortex decreased by 51.2 and 50.6%, respectively. The vortex inside the diverticulum persisted in 18 of 19 subjects. The CFD simulation showed that the flow amplitude generated inside the transverse–sigmoid sinus was segmental, and the largest flow amplitude difference was 20.5 dB. The difference in flow amplitude between the mainstream sinus flow and the diverticular flow was less than 1 dB. In conclusion, the sensation of PT is closely associated with the flow of kinetic energy rather than the formation of a vortex, whereby the amplitude of PT is correlated to the magnitude of the flow velocity and pressure gradient. Additionally, the range of velocity reduction revealed by the RCCD method may serve as a presurgical individual baseline curative marker that may potentially optimize the surgical outcomes.

Diagnostic Approach to Pulsatile Tinnitus: A Narrative Review

Importance

Pulsatile tinnitus is a debilitating symptom affecting millions of Americans and can be a harbinger of hemorrhagic or ischemic stroke. Careful diagnostic evaluation of pulsatile tinnitus is critical in providing optimal care and guiding the appropriate treatment strategy.

Observations

An underlying cause of pulsatile tinnitus can be identified in more than 70% of patients with a thorough evaluation. We advocate categorizing the myriad causes of pulsatile tinnitus into structural, metabolic, and vascular groups. Structural causes of pulsatile tinnitus include neoplasms and temporal bone pathologic abnormalities. Metabolic causes of pulsatile tinnitus include ototoxic medications and systemic causes of high cardiac output. Vascular causes of pulsatile tinnitus include idiopathic intracranial hypertension and dural arteriovenous fistulas. This categorization facilitates a practical evaluation, referral, and treatment pattern.

Conclusions and Relevance

Categorizing the underlying cause of pulsatile tinnitus ensures that dangerous causes of pulsatile tinnitus are not missed, and that patients receive the appropriate care from the proper specialist when needed.

Pediatric tinnitus: The role of neuroimaging

Tinnitus is defined as the perception of sound without an external source and can be categorized as either pulsatile or nonpulsatile (ie, continuous). A variety of etiologies have been reported to cause pediatric tinnitus, many with long-lasting implications due to hearing and concentration impairments. Therefore, imaging can be an essential part of the accurate and timely diagnosis of treatable etiologies. We describe neuroimaging findings in different etiologies of pediatric tinnitus. Etiologies of pulsatile tinnitus are frequently vascular in nature and include vascular loops, congenital vascular anomalies or variants, high riding jugular bulbs with or without a jugular bulb diverticulum, idiopathic intracranial hypertension, aneurysms, internal auditory canal hemangiomas, and petrous apex cephaloceles. Etiologies of continuous tinnitus frequently affect the middle/inner ear structures and include vestibular schwannomas, cholesteatomas, trauma, Chiari malformations, and labyrinthitis ossificans. CT and MR are often complementary modalities: CT is better suited to evaluate the integrity of the temporal osseous structures and MR is better suited to evaluate the vestibulocochlear nerve and to assess for the presence of any masses or malformations. Prompt diagnosis of the etiology of tinnitus in pediatric patients is important to avoid any potential long-term developmental impairments. In the approach to pediatric tinnitus, categorizing the symptoms as either pulsatile versus nonpulsatile and then being aware of the possible causes and imaging findings of either can assist both the clinician and the radiologist in making an expeditious diagnosis.

Hemodynamic mechanism of pulsatile tinnitus caused by venous diverticulum treated with coil embolization

BACKGROUND AND OBJECTIVE

Coil embolization has become a new treatment method for pulsatile tinnitus (PT) caused by sigmoid sinus diverticulum (SSD). Although this therapy has achieved good results in clinical reports, the hemodynamic mechanism of coils in the treatment of PT in SSD remained unclear.

METHODS

Finite element method (FEM) and computational fluid dynamics (CFD) were combined to explore the hemodynamic mechanism of coil embolization in SSD treatment. Three personalized geometric models of sigmoid sinus were established according to the CTA data of patients. Coil model were established by FEM, and the hemodynamic differences of SSD before and after coiling were compared by transient CFD method.

RESULTS

Velocity streamlines disappeared in the SSD after coiling. At the peak time (t1 = 0.22 s), the SSD-average velocity decreased in every patient. The average value of the decreased in three patients was 0.154 ± 0.028 m/s (mean ± SD). Wall average pressure (P_avg) also showed a decline in every patient. Average of decrements of three patients was 17.69 ± 4.91 Pa (mean ± SD). Average WSS (WSS_avg) was also reduced in every patient. The average value of WSS drop was 9.74 ± 3.02 Pa (mean ± SD). After coiling, the proportion of low-velocity region in the sigmoid sinus cortical plate dehiscence (SSCPD) area increased. Average of increments was 22.1 ± 5.36% (mean ± SD).

CONCLUSIONS

A reduction in SSD-average velocity, wall pressure, and WSS were the short-term hemodynamic mechanism of coil embolization for PT. Coil embolization increased the proportion of low-velocity region in the SSCPD area, thereby creating a hemodynamic environment that easily produced thrombus and protects blood vessels from the impact of blood flow. This phenomenon was the long-term effect of coil embolization.

Management of vascular causes of pulsatile tinnitus

Pulsatile tinnitus is a debilitating symptom affecting millions of Americans and can be a harbinger of hemorrhagic or ischemic stroke. Careful diagnostic evaluation of pulsatile tinnitus is critical in providing optimal care and guiding the appropriate treatment strategy. When a vascular cause of pulsatile tinnitus has been established, attention must be focused on the patient's risk of hemorrhagic stroke, ischemic stroke, or blindness, as well as the risks of the available treatment options, in order to guide decision-making. Herein we review our approach to management of the vascular causes of pulsatile tinnitus and provide a literature review while highlighting gaps in our current knowledge and evidence basis.

Brain herniation (encephalocele) into arachnoid granulations: prevalence and association with pulsatile tinnitus and idiopathic intracranial hypertension

PURPOSE

Brain herniation into arachnoid granulations (BHAG) of the dural venous sinuses is a recently described finding of uncertain etiology. The purpose of this study was to investigate the prevalence of BHAG in a cohort of patients with pulsatile tinnitus (PT) and to clarify the physiologic and clinical implications of these lesions.

METHODS

The imaging and charts of consecutive PT patients were retrospectively reviewed. All patients were examined with MRI including pre- and post-contrast T1- and T2-weighted sequences. Images were reviewed separately by three blinded neuroradiologists to identify the presence of BHAG. Their location, signal intensity, size, presence of arachnoid granulation, and associated dural venous sinus stenosis were documented. Clinical records were further reviewed for idiopathic intracranial hypertension, history of prior lumbar puncture, and opening pressure.

RESULTS

Two hundred sixty-two consecutive PT patients over a 4-year period met inclusion criteria. PT patients with BHAG were significantly more likely to have idiopathic intracranial hypertension than PT patients without BHAG (OR 4.2, CI 1.5-12, p = 0.006). Sixteen out of 262 (6%) patients were found to have 18 BHAG. Eleven out of 16 (69%) patients had unilateral temporal or occipital lobe herniations located in the transverse sinus or the transverse-sigmoid junction. Three out of 16 (19%) patients had unilateral cerebellar herniations and 2/16 (13%) patients had bilateral BHAG.

CONCLUSION

In patients with PT, BHAG is a prevalent MRI finding that is strongly associated with the clinical diagnosis of IIH. The pathogenesis of BHAG remains uncertain, but recognition should prompt comprehensive evaluation for IIH.

Effect of Emissary Vein on Hemodynamics of the Transverse- Sigmoid Sinus Junction

Objective: To investigate the effect of the blood flow direction and afflux location of emissary veins (EVs) on the hemodynamics of the transverse-sigmoid sinus (TS-SS) junction.

Methods: A patient-specific geometric model was constructed using computed tomography venography (CTV) and 4D flow MR data from a venous pulsatile tinnitus (PT) patient. New EV models were assembled with the afflux at the superior, middle and inferior portions of the SS from the original model, and inlet and outlet directions were applied. Computational fluid dynamics (CFD) simulation was performed to analyze the wall pressure and flow pattern of the TS-SS junction in each condition.

Results: Compared to the model without EVs, the wall pressure was greatly increased in models with inlet flow and greatly decreased in models with outlet flow. The more closely the EV approached the TS-SS, the larger the pressure in models with inlet flow, and the smaller the pressure in models with outlet flow. The flow streamline in the lateral part of the TS-SS junction was smooth in all models. The streamlines in the medial part were regular spirals in outlet models and chaotic in inlet models. The streamlines showed no obvious changes regardless of afflux location. The velocity at the TS-SS junction of inlet models were uniform, medium-low flow rate, while in control and outlet models were the lateral high flow rate and the central low flow rate.

Conclusion: The flow direction and afflux location of EVs affect the hemodynamics of the TS-SS junction, which may influence the severity of PT.

Pulsatile Tinnitus Due to Stenosis of the Marginal Sinus: Diagnosis and Endovascular Treatment

BACKGROUND AND PURPOSE

Venous pulsatile tinnitus is a disabling condition mainly caused by a stenosis of the lateral sinus. Here, we aimed to report a novel cause of venous pulsatile tinnitus, stenosis of the marginal sinus.

MATERIALS AND METHODS

We retrospectively analyzed patients with isolated venous pulsatile tinnitus for which the suspected cause was a stenosis of the marginal sinus, treated or not, between January 2017 and December 2020. Patient charts and imaging were systematically reviewed. All patients underwent noncontrast temporal bone CT and MR imaging.

RESULTS

Eight patients (7 women; median age, 36 years) were included. Six patients (75%) were overweight, and 1 patient had idiopathic intracranial hypertension. All patients presented with a typical venous pulsatile tinnitus. The stenosis of the marginal sinus was detected using oblique reconstructions on postcontrast 3D MR imaging. There was no other pathologic finding except ipsilateral stenosis of the lateral sinus in 3 patients. Four patients underwent endovascular therapy with placement of a stent in the marginal sinus, leading to complete resolution of the pulsatile tinnitus for all of them. No complication occurred. Of note, the symptoms of intracranial hypertension also regressed after stent placement in that patient.

CONCLUSIONS

Marginal sinus stenosis is a novel cause of venous pulsatile tinnitus, which can be easily detected on MR imaging. Marginal sinus stent placement is safe and efficient. We hypothesized that the marginal sinus stenosis pathophysiology is similar to that of lateral sinus stenosis, which is a common and well-known cause of venous pulsatile tinnitus, explaining the similar clinical presentation and endovascular management.

Diploic vein as a newly treatable cause of pulsatile tinnitus: A case report

BACKGROUND

Pulsatile tinnitus (PT) is an annoying sound that can be eliminated with targeted treatment of the cause. However, the causes of PT have not been fully elucidated.

CASE SUMMARY

A 38-year-old woman with right-sided objective PT underwent preoperative computed tomography arteriography and venography (CTA/V). A 3.8 mm vine diploic vein (DV), which passed through the mastoid air cells posteriorly in a dehiscent canal and was continuous with the transverse-sigmoid sinus, was thought to be the causative finding. Four-dimensional flow magnetic resonance (4D flow MR) imaging showed that the blood in the DV flowed toward the transverse-sigmoid sinus. The closer the blood was to the transverse-sigmoid sinus, the higher the velocity. No vortex or turbulence was found in the DV or adjacent transverse sinus. The sound was eliminated immediately after ligation of the DV with no recurrence during a three-month follow-up. No flow signal of the DV was noted on postoperative 4D flow MR.

CONCLUSION

A DV may be a treatable cause of PT. CTA/V and 4D flow MR could be utilized to determine the morphological and hemodynamic characteristics of the DV.

The Relationships Among Transverse Sinus Stenosis Measured by CT Venography, Venous Trans-stenotic Pressure Gradient and Intracranial Pressure in Patients With Unilateral Venous Pulsatile Tinnitus

Objectives

To assess a non-invasive means of predicting a venous trans-stenotic pressure gradient (TPG) and intracranial pressure (ICP) as opposed to invasive examinations in unilateral venous pulsatile tinnitus (PT) patients.

Methods

Thirty patients with unilateral venous PT who presented symptomatic-sided transverse sinus stenosis (TSS) on computed tomography venography (CTV), ipsilateral TPG measured by digital subtraction angiography (DSA) and cerebrospinal fluid (CSF) pressure measured by lumbar puncture were included. The ratio of TSS was calculated by dividing the cross-sectional areas of the maximal stenosed transverse sinus by that of the adjacent normal transverse sinus on CTV. The correlations among and predictive values of TSS, TPG, and ICP were analyzed.

Results

In patients with unilateral venous PT, the symptomatic-sided and average bilateral TSS values were 78 ± 11 and 77 ± 9%; ICP, 230.50 ± 55.75 mmH₂O; and the TPG, 9.51 ± 5.76 mmHg. The symptomatic-sided TSS was linearly and positively correlated with TPG (R² = 0.400), and the symptomatic-sided and bilateral average TSS both showed weak correlations with ICP (R² = 0.288, R′² = 0.156). When the degree of TSS increased by 10%, the TPG and ICP increased by approximately 3.3 mmHg and 25.8 mmH₂O, respectively. The receiver operating characteristic curve showed the optimal threshold of ipsilateral TSS for a positive TPG was 0.75, while TSS had no significant predictive value for ICP (p > 0.05). TPG and ICP also exhibited a linear positive correlation (R² = 0.552). When ICP increased by 10 mmH₂O, the TPG increased by approximately 0.77 mmHg, and the optimal threshold of ICP for a positive TPG was 227.5.

Conclusion

TSS, TPG, and ICP are interrelated. TSS measured by CTV can predict TPG in patients with unilateral venous PT.

Correlation Between Trans-Stenotic Blood Flow Velocity Differences and the Cerebral Venous Pressure Gradient in Transverse Sinus Stenosis: A Prospective 4-Dimensional Flow Magnetic Resonance Imaging Study

BACKGROUND

The relationship between trans-stenotic blood flow velocity differences and the cerebral venous pressure gradient (CVPG) in transverse sinus (TS) stenosis (TSS) has not been studied.

OBJECTIVE

To evaluate the hemodynamic manifestations of TSS and the relationship between trans-stenotic blood flow velocity differences and the CVPG.

METHODS

Thirty-three patients with idiopathic intracranial hypertension (IIH) or pulsatile tinnitus (PT) and TSS who had undergone diagnostic venography using venous manometry were included in the patient group. Thirty-three volunteers with no stenosis and symptoms were included in the control group. All the 2 groups underwent prospective venous sinus 4-dimensional (4D) flow magnetic resonance imaging (MRI). The average velocity (V_avg) difference and maximum velocity (V_max) difference between downstream and upstream of the TS in 2 groups were measured and compared. Correlations between the CVPG and trans-stenotic V_avg difference/V_max difference/index of transverse sinus stenosis (ITSS) were assessed in the patient group.

RESULTS

The differences in V_avg difference and V_max difference between the patient and control groups showed a statistical significance (P < .001). The V_avg difference and V_max difference had a strong correlation with CVPG (R = 0.675 and 0.701, respectively, P < .001) in the patient group. Multivariate linear regression using the stepwise method showed that the V_max difference and ITSS were correlated with the CVPG (R = 0.752 and R² = 0.537, respectively; P < .001).

CONCLUSION

The trans-stenotic blood flow velocity difference significantly correlates with the CVPG in TSS. As a noninvasive imaging modality, 4D flow MRI may be a suitable screening or complimentary tool to decide which TSS may benefit from invasive venous manometry.

State of the Art: Venous Causes of Pulsatile Tinnitus and Diagnostic Considerations Guiding Endovascular Therapy

Venous variants and pathologic abnormalities are the most common causes of pulsatile tinnitus. These conditions include causes of turbulence within normally located veins and sinuses, and abnormally enlarged or abnormally located veins in close transmissive proximity to the conductive auditory pathway. Such disorders include pathologic abnormalities of the lateral sinus (transverse sinus stenosis and sigmoid sinus wall anomalies), abnormalities and variants of the emissary veins, and anomalies of the jugular bulb and jugular vein. Despite being the most common causes for pulsatile tinnitus, venous variants and pathologic abnormalities are often overlooked in the workup of pulsatile tinnitus. Such oversights can result in delayed patient care and prolonged patient discomfort. Advances in both cerebrovascular imaging and endovascular techniques allow for improved diagnostic accuracy and an increasing range of endovascular therapeutic options to address pulsatile tinnitus. This review illustrates the venous causes of pulsatile tinnitus and demonstrates the associated endovascular treatment. © RSNA, 2021.

Computational fluid dynamics study of the effect of transverse sinus stenosis on the blood flow pattern in the ipsilateral superior curve of the sigmoid sinus

OBJECTIVE

To investigate the effect of different types of transverse sinus stenosis on blood flow patterns in the ipsilateral superior curve of the sigmoid sinus.

METHODS

According to the morphology of transverse and sigmoid sinus sections in pulsatile tinnitus patients, ten idealized models with different degrees and positions of transverse sinus stenosis were constructed. Computational fluid dynamics simulations were performed to compare the hemodynamic characteristics among these models. Follow-up images of previous cases were included, which preliminarily confirmed the hypothesis that bone plate erosion of the sigmoid sinus sulcus is related to blood flow impingement.

RESULTS

Blood flow impingement on the superior curve of the sigmoid sinus wall intensified with increasing degree of stenosis and decreased with increasing distance between the stenosis and the sigmoid sinus. The impact zone was generally confined to the anterior and lateral walls of the superior curve of the sigmoid sinus. When the stenosis was located far from the middle of the transverse sinus, the blood flow impingement on the sigmoid sinus wall was very weak.

CONCLUSIONS

When stenosis is located far from the sigmoid sinus, the causes of tinnitus should be comprehensively considered instead of assuming that stenosis is the main cause. Bone plate erosion of the sigmoid sinus sulcus was promoted by blood flow impingement.

KEY POINTS

• Ten idealized models with different degrees and positions of stenosis were constructed. • The causes of pulsatile tinnitus should be comprehensively considered. • Sigmoid sinus plate dehiscence was promoted by blood flow impingement.

Effects of different morphologic abnormalities on hemodynamics in patients with venous pulsatile tinnitus: A four-dimensional flow magnetic resonance imaging study

The effects of morphologic abnormalities, including sigmoid sinus wall dehiscence (SSWD), transverse sinus stenosis (TSS), and sigmoid sinus diverticulum (SSD), on hemodynamics in venous pulsatile tinnitus (PT) patients have not been established. The aim of this study was to evaluate the effects of SSWD, TSS, and SSD on the hemodynamics of transverse‐sigmoid sinus in venous PT patients. This was a prospective study with 44 venous PT patients and 12 healthy controls. A 3 T/four‐dimensional (4D) flow magnetic resonance imaging with fast field echo was used. Computed tomography arteriography/venography was used to assess ipsilateral SSWD, TSS, and SSD. Maximum velocity (V_max), average velocity (V_avg), and average flow (Flow_avg) were measured. Blood flow patterns were independently assessed by three neuroradiologists. One‐way analysis of variance or Kruskal–Wallis test was also used. On the symptomatic side, all patients had SSWD, 33 patients had TSS, and 22 patients had SSD. Compared with healthy controls, patients with TSS, without TSS, with SSD, and without SSD all showed higher V_max (all p < 0.050), V_avg (all p < 0.050), and Flow_avg (all p < 0.050). Patients with TSS showed higher V_max (p < 0.050) and V_avg (p < 0.050) than those without TSS, and no significant difference in Flow_avg was found between the two groups (p = 0.408). No significant differences in V_max, V_avg, and Flow_avg were found between patients with and without SSD (all p = 1.000). Jet‐like flow in the stenosis and downstream of the stenosis was observed in all patients with TSS. Vortex in SSD was observed in 15 patients with SSD (68%). High blood velocity and flow may be characteristic markers of venous PT. SSWD may be a necessary condition for venous PT. TSS may further increase the blood velocity and form a jet‐like flow. SSD may be related to vortex formation but had no significant effect on blood velocity and flow.

Level of Evidence

2

Technical Efficacy Stage

3

Hemodynamic study of the therapeutic effects of the different degrees of sigmoid sinus diverticulum reconstruction on patients

Sigmoid sinus diverticulum (SSD) is a common pathophysiology of pulsatile tinnitus (PT) and mainly treated by SSD reconstruction surgery. The degree of reconstruction is an important indicator of SSD reconstruction surgery, but its impact on the effect of SSD reconstruction is unclear. This study aimed to clarify the effect of the degree of SSD reconstruction on diverticulum reconstruction surgical treatment. One patient-specific case (control subject) was reconstructed based on the computed tomography angiography (CTA) images of patients with PT. The SSD reconstruction degree was used as a new index in this study. And the case of 30% (case 1), 60% (case 2), and 100% (case 3) of the diverticulum reconstruction degree of control subject were constructed. Transient-state computational fluid dynamics was performed. Wall pressure distribution, wall average pressure (P_avg) of SSD, flow pattern (velocity streamlines and velocity vector), wall shear stress (WSS) and averaged WSS (WSS_avg) were calculated and used in evaluating the hemodynamic differences among the DRD cases. Results demonstrated that change in SSD pressure was not linear with increase in DRD. The DRD that reached 60% of the original diverticulum was effective. At the peak point of the inlet boundary condition (T1 = 0.22s), the P_avg of SSD had a nonlinear change (control subject, 126.967 Pa vs. case 1, 126.274 Pa vs. case 2, 106.897 Pa vs. case 3, 94.116 Pa). Flow vorticity decreased gradually, and the smoothness of the streamlines increased with DRD. WSS_avg slightly changed with increasing DRD. The high-speed flow blood hit the diverticulum entrance and then swirled to hit the area of the sigmoid sinus wall abnormal. It was concluded that flow patterns related to PT differ with DRD. In diverticulum reconstruction surgery, there is a threshold value, and only when the DRD exceeds this value (60% or 70% or 80%), it will have a noticeable effect. In this study, DRD should at least reach 60% of the original diverticulum. When DRD is insufficient, hemodynamic change in the diverticulum is small, and the PT may have remained. SSD may be caused by high-speed blood flow.

Torrents of torment: turbulence as a mechanism of pulsatile tinnitus secondary to venous stenosis revealed by high-fidelity computational fluid dynamics

Background

Pulsatile tinnitus (PT) is a debilitating condition that can be caused by a vascular abnormality, such as an arterial or venous lesion. Although treatment of PT-related venous lesions has been shown to successfully cure patients of the associated ‘tormenting’ rhythmical sound, much controversy still exists regarding their role in the etiology of PT.

Methods

A patient presented with a history of worsening, unilateral PT. A partial venous sinus obstruction related to the large arachnoid granulation was detected on the right side, and subsequently stented at the right transverse sinus. High-fidelity computational fluid dynamics (CFD) was performed on a 3D model digitally segmented from the pre-stent venogram, with assumed pulsatile flow rates. A post-stent CFD model was also constructed from this. Data-driven sonification was performed on the CFD velocity data, blinded to the patient’s self-reported sounds.

Results

The patient reported that the PT was completely resolved after stenting, and has had no recurrence of the symptoms after more than 2 years. CFD simulation revealed highly disturbed, turbulent-like flow at the sigmoid sinus close to auditory structures, producing a sonified audio signal that reproduced the subjective sonance of the patient’s PT. No turbulence or sounds were evident at the stenosis, or anywhere in the post-stent model.

Conclusions

For the first time, turbulence generated distal to a venous stenosis is shown to be a cause of PT. High-fidelity CFD may be useful for identifying patients with such ‘torrents’ of flow, to help guide treatment decision-making.

Patterns of audiometric threshold shifts from pulsatile tinnitus due to sigmoid sinus wall anomalies

PURPOSE

To determine the severity and nature of audiometric threshold shifts for patients with pulsatile tinnitus (PT) due to sigmoid sinus wall anomalies (SSWA).

MATERIALS AND METHODS

38 patients with SSWAs and available pre-operative audiograms were examined. Low- and high-frequency pure tone averages (LF-PTA, HF-PTA) were calculated. Audiometric data were compared between affected and unaffected ears, with the interaural difference (affected-unaffected PTA) representing the change in hearing due to PT. Additionally, post-operative change was examined in 14 patients with available data.

RESULTS

The average pre-operative air conduction (AC) LF-PTA was 17.04 dB on the affected side and 11.38 dB on the unaffected side (p < 0.001). The mean AC HF-PTA was significantly higher on the affected side as well (16.45 dB vs. 14.08 dB, p = 0.008). All shifts were sensorineural, with no significant air-bone gaps, and most subjects still had low-frequency thresholds in the normal range. Though the post-op change was not significant due to attrition, 5/14 patients (35.7%) had complete resolution of their pre-op interaural difference. A similar number developed a HF-PTA post-op threshold elevation in the surgical ear.

CONCLUSIONS

PT due to SSWAs causes a mean 6 dB low-frequency bone-conduction threshold elevation, and smaller high-frequency threshold shifts, due to masking. Patients with larger threshold shifts should have other potential causes of hearing loss explored.

LEVEL OF EVIDENCE

Level IV.

CT venography correlate of transverse sinus stenosis and venous transstenotic pressure gradient in unilateral pulsatile tinnitus patients with sigmoid sinus wall anomalies

Objectives

To investigate the correlation between transverse sinus stenosis (TSS) and transstenotic pressure gradient (TPG) in unilateral pulsatile tinnitus (PT) patients with sigmoid sinus wall anomalies (SSWA).

Methods

Fifty-seven patients with unilateral venous PT were retrospectively included. All of them underwent CT venography and catheter manometry, accompanied with SSWA. The degree, length, shape (intrinsic/extrinsic/dysplasia), location (proximal/middle/distal, referring to the relative position of TSS and the Labbé vein junction) of TSS, the types of SSWA (dehiscence/diverticulum), and the degree of transverse sinus outflow laterality were assessed, and the correlations with ipsilesional TPG were analyzed.

Results

The mean value of ipsilesional TPG was 7.61 ± 0.52 mmHg. The degree and length of ipsilesional TSS were positively correlated with TPG (p < 0.001, p’ < 0.001), respectively. TPG was significantly larger in patients with contralateral transverse sinus dysplasia than those without (p = 0.023) and significantly smaller in patients with ipsilesional sigmoid sinus diverticulum than those with isolated dehiscence (p = 0.001). No statistical difference in TPG was shown between ipsilesional TSSs of different shapes or locations (p > 0.05). No correlation was noted between the degree of ipsilesional transverse sinus outflow laterality and TPG (p = 0.051). Stepwise linear regression indicated that the degree (β = 9.207, 95% CI = 3.558–14.856), length (β = 0.122, 95% CI = 0.025–0.220) of ipsilesional TSS, and contralateral transverse sinus dysplasia (β = 1.875, 95% CI = 0.220–3.530) were significantly correlated with TPG (R² = 0.471).

Conclusions

The degree, length of ipsilesional TSS, and contralateral transverse sinus dysplasia may be used to predict TPG in unilateral PT patients with SSWA.

Key Points

• CT venography may act as a screening tool to help low-probability unilateral pulsatile tinnitus (PT) patients with sigmoid sinus wall anomalies (SSWA) avoid invasive catheter manometry.

• The degree and length of ipsilesional transverse sinus stenosis (TSS) are positively correlated with transtenotic pressure gradient (TPG) in unilateral PT patients with SSWA.

• Ipsilesional TPG is larger in unilateral PT patients with contralateral transverse sinus dysplasia than those without and is smaller in unilateral PT patients with sigmoid sinus diverticulum than those with isolated dehiscence.

Longitudinal analysis of surgical outcome in subjects with pulsatile tinnitus originating from the sigmoid sinus

A dominant sigmoid sinus with either diverticulum or dehiscence (SS-Div/SS-Deh) is a common cause of pulsatile tinnitus (PT). For PT originating from SS-Div/SS-Deh, an etiology-specific and secure reconstruction using firm materials is vital for optimal outcomes. As a follow-up to our previous reports on transmastoid SS resurfacing or reshaping for SS-Div/SS-Deh, this study aimed to evaluate the long-term results of transmastoid resurfacing/reshaping. We retrospectively reviewed 20 PT patients who were diagnosed with SS-Div/SS-Deh, underwent transmastoid resurfacing/reshaping, and were followed up for more than 1 year postoperatively. For PT, immediate and long-term changes (> 1 year) in loudness and annoyance were analyzed using the visual analog scale (VAS). Additionally, pre and postoperative objective measurements of PT using transcanal sound recording and spectro-temporal analysis (TSR-STA), imaging results, and audiological findings were comprehensively analyzed. Significant improvements in PT were sustained or enhanced for > 1 year (median follow-up period: 37 months, range: 12–54 months). On TSR-STA, both peak and root mean square amplitudes decreased after surgery. Also, the average pure-tone threshold at 250 Hz improved after surgery. Thus, our long-term follow-up data confirmed that the surgical management of PT originating from SS-Div/SS-Deh is successful with regard to both objective and subjective measures.

Why does unilateral pulsatile tinnitus occur in patients with idiopathic intracranial hypertension?

PURPOSE

To investigate the relevant factors of unilateral pulsatile tinnitus (PT) in patients with idiopathic intracranial hypertension (IIH) using CT.

METHODS

CT angiography images of IIH patients with unilateral PT (n = 19), without PT (n = 13), and controls (n = 32) were reviewed. The characteristics including transverse sinus stenosis (TSS), venous outflow laterality (VOL), sigmoid sinus wall dehiscence (SSWD), and sigmoid sinus diverticulum (SSD) were quantitatively or/and qualitatively detected. VOL was compared between the symptomatic side of IIH patients with PT and the larger side of IIH patients without PT and the controls. TSS, SSWD, and SSD were compared between the symptomatic side of IIH patients with PT, and both sides of the latter two groups.

RESULTS

There was no statistical difference in body mass index or cerebrospinal fluid pressure between IIH patients with and without PT. The prevalence of TSS was significantly higher in IIH patients than that in the controls (p = 0.000), but TSS had no correlation with PT within IIH patients. The prevalence of SSWD successively decreased in IIH patients with PT, without PT, and the controls, with significant differences between each two of three groups (p = 0.000, p' = 0.000, p″ = 0.031). The proportion of VOL and the prevalence of SSD were significantly larger in IIH patients with PT than in the latter groups respectively (p_VOL = 0.005, p'_VOL = 0.000; p_SSD = 0.040, p'_SSD = 0.000). All SSDs in IIH patients with PT were accompanied with SSWD.

CONCLUSION

The dominant VOL and ipsilateral SSWD with/without SSD may be correlated with the occurrence of unilateral PT in IIH patients.

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_avg) and time-average P_avg (TAP_avg) on the SSWA area were studied, the TAP_avg difference pre- and postoperation between the two groups was found significant (p = 0.0021). The TAP_avg 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_avg 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 (TAV_avgV) 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.

Sound Measurement in Patient-Specific 3D Printed Bench Models of Venous Pulsatile Tinnitus

HYPOTHESIS

We hypothesize patient-specific flow models to be an adequate in vitro surrogate to allow for characterization of pulsatile tinnitus (PT) that affects three to five million Americans.

BACKGROUND

PT, rhythmic sounds without an extracorporeal source that patients appreciate, can be caused by aberrant blood flow in large cerebral veins near the cochlea. To investigate the sound production mechanism, we created 3D printed flow models based on patient-specific cerebral venous anatomies.

METHODS

Magnetic resonance angiography datasets from two patients with PT were used to generate patient-specific 3D printed flow models. A flow circuit connecting the patient-specific models to a pulsatile, continuous flow pump simulating cardiac cycle was created. Sound recordings were made along the surface of the models using an electronic stethoscope. Peak-to-rms amplitude, and area under the power spectral density (PSD) curve values were computed to evaluate the sound measurements. Wilcoxon rank sum test was used to statistically determine the differences in measurements between the patient-specific models.

RESULTS

In patient-1, the recordings (peak-to-rms) from the internal jugular vein stenosis of baseline model (4.29 ± 1.26 for 146 samples) were significantly louder (p < 0.001) than that of the altered model (3.29 ± 0.96 for 143 samples). In patient-2, the sound measured at the transverse sinus stenosis in the pre-lumbar puncture model (4.84 ± 1.11 for 148 samples) was significantly louder (p < 0.0001) than that of the post-lumbar puncture model (3.14 ± 0.87 for 135 samples).

CONCLUSIONS

The models are able to generate sounds very similar to those appreciated by patients and examiners in the cases of objective PT.