An in vitro experimental study on the relationship between pulsatile tinnitus and the dehiscence/thinness of sigmoid sinus cortical plate

Fluid-structure interaction study on the causes of mending material damage after sigmoid sinus wall reconstruction

BACKGROUND AND OBJECTIVE

Sigmoid Sinus (SS) Wall Reconstruction (SSWR) is the mainstream treatment for pulsatile tinnitus (PT), but it has a high risk of recurrence. The damage of mending material is the key cause of recurrence, and its hemodynamic mechanism is still unclear. The purpose of this study was to investigate the hemodynamic causes of mending material breakage.

METHODS

In this study, six patient-specific geometric models were reconstructed based on the data of the computed tomography angiography (CTA). The transient fluid-structure coupling method was performed to clarify the hemodynamic state of sigmoid sinus and the biomechanical state of the mending material. The distribution of stress and displacement and the flow pattern were calculated to evaluate the hemodynamic and biomechanics difference at the mending material area.

RESULTS

The area of blood flow impact in some patients (2/6) was consistent with the damaged location of the mending material. The average stress (6/6) and average displacement (6/6) of damaged mending material were higher than those of complete mending material. All (6/6) patients showed that the high-stress and high-displacement proportion of the DMM region was higher than that of the CMM region. Moreover, the average stress fluctuation (6/6) and average displacement (6/6) fluctuation degree of damaged mending material is larger than that of complete mending material.

CONCLUSIONS

The impact of blood and the uneven stress and displacement fluctuation of the mending material may be the causes of mending material damage. High stress and high displacement might be the key causes of the mending material damage.

Influence of sigmoid plate and dura mater on vascular wall displacement, vibroacoustic/hydroacoustic sources characteristics, and frequency-loudness assessments of venous pulsatile tinnitus: A coupled-computational fluid dynamics study combining transcanal recording investigation

Investigations of pulsatile tinnitus (PT) caused by sigmoid sinus wall anomalies (SSWAs) using computational fluid dynamics (CFD) have recently increased in prevalence. However, accurate modeling of anatomical structures regarding sigmoid plate dehiscence and acoustic sources of PT remains lacking. This study incorporates coupled CFD techniques, micro-computed tomography, and scanning electron microscope to reveal the vibroacoustic and hydroacoustic sources and displacement characteristics of the transverse-sigmoid sinus system. Furthermore, the in vivo transcanal-recording technique combined with ipsilateral internal jugular vein compression was implemented to cross-reference the captured acoustic profile of PT with the calculated results. In this study, the transient state coupled CFD technique was used to calculate the vibroacoustic and hydroacoustic sources. The dehiscent sigmoid plate and periosteal dura mater were then reconstructed. The displacement characteristics and acoustic results were analyzed. The displacement of the vascular wall underneath the dehiscent area was 9.6 times larger than that of the sigmoid plate and 3,617 times smaller than that of the vascular wall without the overlying osseous structures. The peak amplitude of flow-induced vibroacoustic noise was 119.3 dB at 20.2 Hz measured at the transverse sinus. Within the observed 20–1,000 Hz frequency range, the largest peak amplitude of hydroacoustic noise was 80.0 dB at 20.2 Hz located at the jugular bulb region. The simulated results conformed with the in vivo acoustic profile which the major frequency of PT falls within 1,000 Hz. In conclusion, 1) the sigmoid plate and dura mater greatly impact vascular wall displacement, which should not be overlooked in CFD simulations. 2) By incorporating the transcanal recording technique with IJV compression test, the primary frequency of PT was found fluctuating below 1,000 Hz, which matches the frequency component simulated by the current CFD technique; amplitude-wise, however, the peak amplitude of in vivo pulse-synchronous somatosound measures approximately 10 dB, which is comparatively lesser than the CFD results and the subjectively perceived loudness of PT. Thus, the transmission pathway, intramastoid acoustic impedance/amplification effect, and the perceptive threshold of PT require further investigations to minimize the incidence of surgical failure.

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.

Therapeutic Validation of Venous Pulsatile Tinnitus and Biomaterial Applications for Temporal Bone Reconstruction Surgery Using Multi-sensing Platforms and Coupled Computational Techniques

The application of grafts and biomaterials is a cardinal therapeutic procedure to resolve venous pulsatile tinnitus (PT) caused by temporal bone dehiscence during transtemporal reconstructive surgery. However, the transmission mechanism of venous PT remains unclear, and the sound absorption and insulation properties of different repair materials have not been specified. This study quantifies the vibroacoustic characteristics of PT, sources the major transmission pathway of PT, and verifies the therapeutic effect of different material applications using joint multi-sensing platforms and coupled computational fluid dynamics (CFD) techniques. The in vivo intraoperative acoustic and vibroacoustic characteristics of intrasinus blood flow motion and dehiscent sigmoid plate of a typical venous PT patient were investigated using acoustic and displacement sensors. The acoustical, morphological, and mechanical properties of the dehiscent sigmoid plate, grafts harvested from a cadaveric head, and other biomaterials were acquired using acoustical impedance tubes, micro-CT, scanning electron microscopy, and mercury porosimetry, as appropriate. To analyze the therapeutic effect of our previous reconstructive techniques, coupled CFD simulations were performed using the acquired mechanical properties of biomaterials and patient-specific radiologic data. The peak in vivo intraoperatively gauged, peak simulated vibroacoustic and peak simulated hydroacoustic amplitude of PT prior to sigmoid plate reconstruction were 64.0, 70.4, and 72.8 dB, respectively. After the solidified gelatin sponge–bone wax repair technique, the intraoperative gauged peak amplitude of PT was reduced from 64.0 to 47.3 dB. Among three different reconstructive techniques based on CFD results, the vibroacoustic and hydroacoustic sounds were reduced to 65.9 and 68.6 dB (temporalis–cartilage technique), 63.5 and 63.1 dB (solidified gelatin sponge technique), and 42.4 and 39.2 dB (solidified gelatin sponge–bone wax technique). In conclusion, the current novel biosensing applications and coupled CFD techniques indicate that the sensation of PT correlates with the motion and impact from venous flow, causing vibroacoustic and hydroacoustic sources that transmit via the air-conduction transmission pathway. The transtemporal reconstructive surgical efficacy depends on the established areal density of applied grafts and/or biomaterials, in which the total transmission loss of PT should surpass the amplitude of the measured loudness of PT.

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.

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.

Associations among Audiometric, Doppler Hydroacoustic, and Subjective Outcomes of Venous Pulsatile Tinnitus

OBJECTIVE

Venous pulsatile tinnitus (PT) has received increasing attention recently. As analyses of psychophysical and neuropsychological dimensions of venous PT are lacking, this study aimed to quantitatively and qualitatively investigate the correlation among audiometric, hydroacoustic, and subjective outcomes in patients with PT.

METHODS

Fifty-five venous PT patients, with or without sigmoid sinus wall anomalies (SSWAs), were subdivided into SSWAs (n = 30) and non-SSWAs (n = 25) groups. Audiometric and hemodynamic evaluations were assessed. Questionnaires including the Tinnitus Handicap Inventory, Hospital Anxiety and Depression Scale (HADS), and Athens Insomnia Scale (AIS) were deployed to evaluate the psychological impacts of PT.

RESULTS

Among 55 subjects, PT frequency-related pure-tone audiometry (PTA) was significantly different between ipsilesional non-PT frequency-related PTA (p < 0.01), ipsilateral jugular vein compression PTA (p < 0.01), and contralesional ear PTA (p < 0.01). In contrast with the pulsatility index and flow velocity, bilateral EOET and flow volume were significantly different (p < 0.01). Of the 3 questionnaire types, there was a strong correlation between HADS anxiety and AIS scores (r = 0.658, p < 0.01). The duration of PT was not correlated with subjective outcomes, and there was no statistical significance found among audiometric, hemodynamic, and subjective outcomes between SSWAs and non-SSWAs groups.

CONCLUSIONS

(1) The duration of PT was irrelevant to the increase of PTA. (2) Venous PT is the perception of vascular flow sound, in which hydroacoustic characteristics can be highly independent. (3) Anxiety, depression, and sleep disorders commonly prevail among PT patients.

Bone remodeling in sigmoid sinus diverticulum after stenting for transverse sinus stenosis in pulsatile tinnitus: A case report

BACKGROUND

Pulsatile tinnitus (PT) is a potentially disabling symptom that has received increasing attention. Multiple causes of PT have been confirmed by targeted treatment. However, dynamic changes of related structures in PT patients with multiple causes after stenting for ipsilateral transverse sinus stenosis (TSS) have not been previously reported. We report such a case and present postoperative computed tomography venography (CTV) follow-up findings to demonstrate the decreased sigmoid sinus diverticulum and bone remodeling.

CASE SUMMARY

A 45-year-old man suffered from left-sided PT for 15 years that was occasionally accompanied by headache and dizziness. Pre-operative CTV revealed left-sided sigmoid sinus wall anomalies (SSWAs), TSS, outflow dominance, large posterior condylar emissary vein, and an empty sella turcica. A cerebrospinal fluid pressure of 270 mmH₂O was further detected. The sound disappeared immediately after stenting for ipsilateral TSS, with no recurrence during 2 years of follow-up. After the procedure, the patient underwent four consecutive CTV examinations. The diverticulum decreased 6 mo after the procedure with new bone remodeling. The density of the remodeled bone was further increased 1 year later, and a hardened edge was formed 2 years later.

CONCLUSION

PT associated with SSWAs, TSS, and idiopathic intracranial hypertension can be cured by stenting for TSS alone. And bone remodeling around SSWAs is a more significant finding.

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

Hydroacoustic analysis and extraluminal compression surgical insights of venous pulsatile tinnitus

OBJECTIVE

This study aimed to quantitatively and qualitatively evaluate the hydroacoustic changes from "presence" to "disappearance" of pulsatile tinnitus (PT) with the extraluminal compression surgical technique. The recent issues of concern pertaining to the hydroacoustic characteristics of sigmoid sinus wall anomalies and distal transverse sinus stenosis (dTSS) were discussed.

METHODS

This study was based on a retrospective case series. Seventy-seven patients with PT and transverse-sigmoid sinus enlargement with or without transverse-sigmoid sinus junction anomalies and transverse sinus stenosis (TSS) who had undergone extraluminal compression surgery under local anesthesia were included. Management of intractable intraoperative challenges and techniques for reversal extraluminal compression were introduced. Anatomical measurements, intraoperative color-coded Doppler ultrasonography, spectro-temporal analysis, and computational fluid dynamics were employed to analyze the hydroacoustic characteristics of PT.

RESULTS

The efficacy of the extraluminal compression technique was evident with the significant reduction in peak turbulent kinetic energy, vorticity, and mean pressure gradient at the transverse-sigmoid junction, resulting in over 20% reduction in PT amplitude. dTSS is a common finding in patients with PT exhibiting transverse-sigmoid sinus enlargement. Patients with dTSS presented with significant differences in hemodynamic characteristics as compared to those without. Linear regression analysis showed that the flow disturbance (turbulent kinetic energy and vorticity) was closely associated with the degree of dTSS, whereas the flow amplitude was not related to the degree or location of TSS. Low-pulsatory vortex flow at the transverse-sigmoid junction was visualized during an intraoperative color-coded Doppler examination, and the displayed low-frequency PT sound corresponded to the patients' subjective perception of PT.

CONCLUSION

(1) A reduction of over 20% of the flow-induced noise is the therapeutic goal of extraluminal compression technique. Since reductions in the magnitude of hemodynamic parameters, including turbulent kinetic energy, vorticity, and mean pressure gradient, render the flow-induced noise inaudible, besides sigmoid sinus wall anomalies, it is likely that PT develops from the aggregation of flow-based pathologies. (2) Although dTSS and diverticulum may greatly affect the hemodynamics at the transverse-sigmoid junction, in contrast to dehiscence, dTSS and diverticulum may not be the limiting factors for PT development.

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.

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.

Extraluminal Sigmoid Sinus Angioplasty: A Pertinent Reconstructive Surgical Method Targeting Dural Sinus Hemodynamics to Resolve Pulsatile Tinnitus

OBJECTIVES

1) To provide information on the treatment of pulsatile tinnitus (PT) with transtemporal extraluminal sigmoid sinus angioplasty (ESSA); and 2) to discuss the current clinical management of PT.

STUDY DESIGN

This was a retrospective study.

SETTINGS

Multi-institutional tertiary university medical centers.

PATIENTS

Fifty-four PT patients with transverse-sigmoid sinus enlargement and prominent transverse-sigmoid junction with or without sigmoid sinus wall anomalies or transverse sinus anomalies.

INTERVENTION

All patients underwent ESSA under local anesthesia.

MAIN OUTCOME MEASURES

Intraoperative discoveries and surgical resolution of PT, morphology, and computational fluid dynamics.

RESULTS

Fifty-three of the 54 (98%) patients experienced a significant reduction in, or complete resolution of, PT after ESSA. No major surgical complications occurred, except for one case where we observed a full collapse of the sinus wall. On average, this surgery reduced the cross-sectional area at the transverse-sigmoid junction by 61.5%. Our intraoperative discoveries suggest that sigmoid sinus wall anomalies may not be a definitive cause of PT. The transverse-sigmoid sinus system was significantly larger (in term of both cross-sectional area and volume) on the ipsilesional side compared with the contralesional side. Following ESSA, the vascular wall pressure and vortex flow at the transverse-sigmoid junction decreased considerably, and the flow velocity and wall shear stress increased significantly.

CONCLUSION

ESSA is a highly effective surgical technique for PT patients with transverse-sigmoid sinus enlargement and prominent transverse-sigmoid junction, regardless of whether they also have sigmoid sinus wall or transverse sinus anomalies. A large transverse-sigmoid system with prominent transverse-sigmoid junction is a predisposing factor for PT, and only by improving patients' intrasinus hemodynamics could PT be resolved efficiently. In cases without complete obstruction of venous return, ESSA is safe. No postoperative complications related to neurological disorders were observed.

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.