Intracranial venous sinus stenosis: hemodynamic assessment with two-dimensional parametric parenchymal blood flow software on digital subtraction angiography.

OBJECTIVE: Intracranial venous sinus stenosis (IVSS) is the most common finding associated with idiopathic intracranial hypertension. A pressure gradient >8-10 mm Hg across the stenosis is considered hemodynamically significant, and typically responds to endovascular stent treatment. Here we assess the venous hemodynamics with two-dimensional (2D) parametric parenchymal blood flow software (Siemens-Healthineers, Forchheim, Germany) and its ability to predict significant IVSS. METHODS: Patients with IVSS treated at our institution between 2013 and 2018 were retrospectively reviewed. Measurements of contrast transit time on DSA were calculated with 2D parametric parenchymal blood flow software. Values were obtained proximally and distally to the stenotic region. Venous Stenosis Index (VSI) was defined as the ratio of the area under the curve (AUC) in the pre-stenotic vessel to the AUC in the post-stenotic vessel. VSI was compared between the stenotic and control groups at baseline, and before and after stent deployment in the stenotic group. The accuracy of VSI was assessed using the non-parametric receiver operating characteristic (ROC) curve. RESULTS: 11 patients with IVSS treated with venous stent deployment were included. Patients in the control group were similar in age, gender, and absence of major comorbidities. VSI in the IVSS group was significantly higher at baseline compared with the control group (1.42 vs 0.97, p=0.01). Area under the ROC was 0.82. After stent deployment, VSI decreased significantly compared with baseline (1.04 vs 1.42, p<0.01). CONCLUSION: 2D parametric parenchymal blood flow software is a useful tool which can accurately evaluate significant hemodynamic venous stenosis without intracranial catheterization, added radiation exposure, additional contrast injection, and periprocedural risks.

Computational Fluid Dynamics-Based Blood Flow Assessment Facilitates Optimal Management of Portal Vein Stenosis After Liver Transplantation.

BACKGROUND: Portal vein stenosis develops in 3.4-14% of split liver transplantation1-3 and its early detection and treatment are essential to achieve long-term graft survival,2-5 although the diagnostic capability of conventional modalities such as Doppler ultrasound and computed tomography is limited.1,4,5 METHODS: This study used computational fluid dynamics to analyze portal vein hemodynamics in the management of post-transplant portal vein stenosis. To perform computational fluid dynamics analyses, three-dimensional portal vein model was created using computed tomographic DICOM data. The inlet flow condition was set according the flow velocity measured on Doppler ultrasonography. Finally, portal vein flow was simulated on a fluid analysis software (Software Cradle, Japan). RESULTS: An 18-month-old girl underwent liver transplantation using a left lateral graft for biliary atresia. At the post-transplant 1-week evaluation, the computational fluid dynamics streamline analysis visualized vortices and an accelerated flow with a velocity ratio < 2 around the anastomotic site. The wall shear stress analysis revealed a high wall shear stress area within the post-anastomotic portal vein. At the post-transplant 6-month evaluation, the streamline analysis illustrated the increased vortices and worsening flow acceleration to reach the proposed diagnostic criteria (velocity ratio > 3:1).3,5 The pressure analysis revealed a positive pressure gradient of 3.8 mmHg across the stenotic site. Based on the findings, the patient underwent percutaneous transhepatic portal venoplasty with balloon dilation. The post-treatment analyses confirmed the improvement of a jet flow, vortices, a high wall shear stress, and a pressure gradient. DISCUSSION: The computational fluid dynamics analyses are useful for prediction, early detection, and follow-up of post-transplant portal vein stenosis and would be a promising technology in post-transplant management.

Assessment of cerebral infarction after transient cerebral ischemic attack by ABCD2 score combined with the position of intracranial vascular stenosis.

This study aims to investigate the value of the ABCD score combined with the position of the offending vessel stenosis in predicting the risk of transient ischemic attack (TIA) to develop into cerebral infarction.The ABCD score and head magnetic resonance imaging + magnetic resonance angiography (MRA) results of 192 patients with TIA were retrospectively analyzed. With the 7th day as the endpoint time, these patients were divided into 3 groups, according to ABCD scores: low-risk group (n = 105), moderate-risk group (n = 60), and high-risk group (n = 27). Blood vessels were screened using head MRA results, and patients were accordingly divided into 2 groups: proximal vascular stenosis group (n = 71) and nonproximal vascular stenosis group (n = 171). Then, the association of the position of the intracranial vascular stenosis and ABCD score with short-term prognosis was analyzed.Based on the ABCD score, the incidence of cerebral infarction after 1 week was significantly higher in the high-risk group (85.7%) than in the moderate-risk group (16.7%) and low-risk group (1.9%), and the differences were statistically significant (P < .05). When the ABCD score was ≥4 points, the incidence of cerebral infarction after 1 week was significantly higher in the proximal vascular stenosis group (59.1%) than in the nonproximal vascular stenosis group (30.8%), and the difference was statistically significant (P < .05). When the ABCD score was <4 points, the incidence of cerebral infarction after 1 week in the proximal stenosis group (2%) was not significantly different from that in the nonproximal stenosis group (1.9%, P > .05).The ABCD score combined with proximal offending vessel stenosis can improve the short-term prediction of cerebral infarction in patients with TIA.

Fluid dynamic assessment of tracheal flow in infants with congenital tracheal stenosis before and after surgery.

Tracheal flow in infants with congenital tracheal stenosis (CTS) was numerically investigated using subject-specific airway models before and after reconstructive surgery. We quantified tracheal flow based on airway resistance during inhalation, and compared it between controls and patients before and after surgery. The airway resistance in each subject was assessed using geometrical parameters of the trachea: the minimum cross-sectional area Amin, the minimum cross-sectional area normalized by the standard deviation of the cross-sectional area Amin/σA, the area ratio of the minimum and maximum cross-sectional area Amin/Amax, and ratio of the normalized standard deviation of cross-sectional area to the mean cross-sectional area σA/Amean. Our numerical results demonstrated that such geometrical parameters could be used to assess the severity of CTS. Since subjects can be more clearly categorized as controls and most preoperative patients in terms of the airway resistance, a simulation using subject-specific airway models can lead us to a precise understanding of tracheal flow, and also provide knowledge about therapeutic decision. Our numerical results also demonstrated that significant surgical expansion of cross-sectional area did not help recover tracheal flow because of expansion loss. These results will be helpful not only when making therapeutic decisions about surgery but also when assessing quality of life in postoperative patients. Graphical abstract.

Reactive hyperemia-peripheral arterial tonometry is useful for assessment of not only endothelial function but also stenosis of the digital artery.

BACKGROUND: Although reactive hyperemia-peripheral arterial tonometry (RH-PAT) is widely used for assessment of endothelial function, RH index (RHI) cannot be measured in some cases when pulse wave amplitude (PWA) is very low. Decrease in PWA is mainly caused by proper palmar digital artery (PPDA) stenosis. The purpose of this study was to evaluate the relationship between PWA measured by RH-PAT and stenosis of the PPDA measured by digital subtraction angiography and to evaluate the limitation of assessment of endothelial function measured by RHI in patients with PPDA stenosis. METHODS: We measured baseline PWA in 51 fingers including the first to third fingers of both hands in 10 patients who had PPDA stenosis and in 66 fingers that were the first fingers of both hands in 33 subjects who had no PPDA stenosis. Severe stenosis was defined as over 75% by lower percent diameter stenosis between two PPDAs in a finger. RESULTS: PWA was significantly correlated with stenosis of the digital artery (r=-0.55; P<0.0001). A PWV value of 300mV was the optimal cut-off value for severe stenosis (sensitivity, 84.0%; specificity, 88.5%). Log RHI was significantly lower in patients with PPDA stenosis than in subjects without PPDA stenosis (0.33±0.27 versus 0.73±0.27, P=0.007). CONCLUSIONS: RH-PAT may be useful for assessment of not only endothelial function but also PPDA stenosis. RHI may be underestimated in patients with PPDA stenosis. We should pay attention to low baseline PWA when measuring RHI. CLINICAL TRIAL REGISTRATION INFORMATION: URL for clinical trial: http://UMIN; registration number for clinical trial: UMIN000003409.

Assessment of Reynolds stress components and turbulent pressure loss using 4D flow MRI with extended motion encoding.

PURPOSE: To measure the Reynolds stress tensor using 4D flow MRI, and to evaluate its contribution to computed pressure maps. METHODS: A method to assess both velocity and Reynolds stress using 4D flow MRI is presented and evaluated. The Reynolds stress is compared by cross-sectional integrals of the Reynolds stress invariants. Pressure maps are computed using the pressure Poisson equation-both including and neglecting the Reynolds stress. RESULT: Good agreement is seen for Reynolds stress between computational fluid dynamics, simulated MRI, and MRI experiment. The Reynolds stress can significantly influence the computed pressure loss for simulated (eg, -0.52% vs -15.34% error; P < 0.001) and experimental (eg, 306 ± 11 vs 203 ± 6 Pa; P < 0.001) data. A 54% greater pressure loss is seen at the highest experimental flow rate when accounting for Reynolds stress (P < 0.001). CONCLUSION: 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.

Physiological assessment of left main coronary artery disease.

The left main coronary artery (LMCA) is responsible for supplying the majority of the left ventricular myocardium. Visual estimation of stenosis severity on angiography has major limitations and methods to assess functional significance, such as fractional flow reserve (FFR), have been shown to yield better outcomes; however, to date, major trials examining the use of such physiological indices have excluded LMCA disease. Furthermore, LMCA disease commonly co-exists with downstream disease, which complicates the interpretation of coronary physiological data. This review summarises existing evidence for physio-|logy-guided management of LMCA disease. It will also explore the difficulties posed when functionally assessing LMCA lesions and outline potential solutions. Finally, we aim to provide insight into how novel physiological tools may improve the management of LMCA disease in the future.

Stenosis in Middle Cerebral Artery Duplication: Assessment With Transcranial Color-Coded Duplex Sonography.

Duplication of the middle cerebral artery is an unusual anatomic variant. Stenosis of one of its branches can be an exceptional cause of stroke and is very difficult to diagnose with transcranial duplex sonography. We report 2 patients with duplication of the middle cerebral artery in whom stenosis of one of its branches led to ischemic stroke and describe the sonographic findings in comparison to other neuroimaging modalities. These cases highlight the utility of adding a coronal insonation plane on top of the traditional axial plane to avoid identification pitfalls in patients with anatomic variants.

[Laparoscopic treatment of median arcuate ligament syndrome (MALS) -- case report]. / Truncus coeliacus compressiós szindróma laparoscopos mutéti megoldása -- Esetismertetés.

CASE REPORT: The authors report a case of a 34-year-old woman who had postprandial abdominal pain for years. During the course of her examination lactose intolerance and hiatus hernia was diagnosed. After ineffective conservative treatment CT angiography (CTA) and digital substraction angiography (DSA) was performed and showed significant celiac artery stenosis. Percutaneous transluminal angioplasty (PTA) was unsuccessful as extravasal mechanical compression was present, therefore, laparoscopic decompression and surgical division of MAL fibres were carried out. The postoperative period was characterized by a complete relief of previous symptoms and repeated CTA showed normal blood flow. DISCUSSION: The authors emphasize the importance of the measurement of peak velocity of celiac trunk with Colour Duplex abdominal ultrasonography, the examination has 100% sensitivity and 83% specificity. The Duplex ultrasonography is less expensive than the "gold standard" diagnostic methods like CT and DS angiography, and can lead us to early diagnosis. Laparoscopic surgery is safe and low expense method for celiac artery decompression, however, sometimes it is difficult to reveal the exact reason and thus setting up the proper operation plan.

[Assessment of chronic obstructive eustachian tube dysfunction : Evaluation of the German version of the Eustachian Tube Dysfunction Questionnaire]. / Beurteilung der chronisch-obstruktiven Tubenfunktionsstörung : Evaluation des "Eustachian Tube Dysfunction Questionnaire" in der deutschen Übersetzung.

BACKGROUND: Eustachian tube dysfunction can cause middle ear diseases and impair quality of life. Sufficient diagnostic tools for chronic obstructive eustachian tube dysfunction are lacking and not reliable enough. PATIENTS AND METHODS: The Eustachian Tube Dysfunction Questionnaire (ETDQ-7) was published by McCoul et al. in 2012 as an instrument to evaluate eustachian tube function. They demonstrated the reliability und validity of their questionnaire. The cut-off point for the diagnosis of eustachian tube dysfunction is ≥ 14.5 at 100 % sensitivity and 100 % specificity. We translated the ETDQ-7 into German and used it on 100 healthy subjects and 43 patients with chronic obstructive eustachian tube dysfunction. RESULTS: The results in the English questionnaire were confirmed by our examinations with the German version of the questionnaire. The mean ETDQ-7 score was 8.67 in the healthy subjects and 24.7 in the patients with chronic obstructive eustachian tube dysfunction. The area under the curve in ROC analysis was 98.8 % (p < 0.0001). CONCLUSION: We recommend the ETDQ-7 as an addition to patient history in the examination of eustachian tube dysfunction. It may as well be valuable in follow-up examinations to monitor treatment success.

Assessment of regional lung ventilation by electrical impedance tomography in a patient with unilateral bronchial stenosis and a history of tuberculosis / Avaliacao da ventilacao pulmonar regional por tomografia de impedancia eletrica em paciente com estenose bronquica unilateral pos-tuberculose

Bronchial stenosis can impair regional lung ventilation by causing abnormal, asymmetric airflow limitation. Electrical impedance tomography (EIT) is an imaging technique that allows the assessment of regional lung ventilation and therefore complements the functional assessment of the lungs. We report the case of a patient with left unilateral bronchial stenosis and a history of tuberculosis, in whom regional lung ventilation was assessed by EIT. The EIT results were compared with those obtained by ventilation/perfusion radionuclide imaging. The patient was using nasal continuous positive airway pressure (CPAP) for the treatment of obstructive sleep apnea syndrome. Therefore, we studied the effects of postural changes and of the use of nasal CPAP. The EIT revealed heterogeneous distribution of regional lung ventilation, the ventilation being higher in the right lung, and this distribution was influenced by postural changes and CPAP use. The EIT assessment of regional lung ventilation produced results similar to those obtained with the radionuclide imaging technique and had the advantage of providing a dynamic evaluation without radiation exposure.

A estenose brônquica pode comprometer a ventilação pulmonar regional devido a limitações anormais e assimétricas ao fluxo aéreo. A tomografia de impedância elétrica (TIE) é uma técnica que possibilita a avaliação da ventilação pulmonar regional por imagem e, portanto, pode complementar a avaliação funcional dos pulmões. Relatamos o caso de uma paciente com estenose brônquica unilateral à esquerda, pós-tuberculose, em que se avaliou a ventilação pulmonar regional através da TIE, relacionando-a com a cintilografia de ventilação/perfusão. Foram estudados os efeitos das mudanças posturais e da aplicação de continuous positive airway pressure (CPAP, pressão positiva contínua nas vias aéreas) nasal, uma vez que a paciente usava esse tratamento para síndrome da apneia obstrutiva do sono. A TIE demonstrou distribuição heterogênea da ventilação pulmonar regional com maior ventilação no pulmão direito, sendo essa distribuição influenciada pelas mudanças de decúbitos e pela aplicação de CPAP. A análise da ventilação pulmonar regional pela TIE se mostrou similar aos achados da cintilografia pulmonar de ventilação com a vantagem de possibilitar uma avaliação dinâmica e sem exposição à radiação.

Renal artery stenosis: prevalence of, risk factors for, and management of in-stent stenosis.

Atherosclerotic renal artery stenosis is common and is associated with hypertension and chronic kidney disease. More frequent use of percutaneous renal artery stent placement for the treatment of renal artery stenosis during the past 2 decades has increased the number of patients with implanted stents. In-stent stenosis is a serious problem, occurring more frequently than earlier reports suggest and potentially resulting in late complications. Currently, there are no guidelines covering the approach to restenosis after renal artery stent placement. This article reviews data on the prevalence of and risk factors for the development of in-stent stenosis and the clinical manifestations, evaluation, and treatment of in-stent stenosis and suggests a strategy for the management of patients after percutaneous renal artery stent placement.

Assessment of regional lung ventilation by electrical impedance tomography in a patient with unilateral bronchial stenosis and a history of tuberculosis.

Bronchial stenosis can impair regional lung ventilation by causing abnormal, asymmetric airflow limitation. Electrical impedance tomography (EIT) is an imaging technique that allows the assessment of regional lung ventilation and therefore complements the functional assessment of the lungs. We report the case of a patient with left unilateral bronchial stenosis and a history of tuberculosis, in whom regional lung ventilation was assessed by EIT. The EIT results were compared with those obtained by ventilation/perfusion radionuclide imaging. The patient was using nasal continuous positive airway pressure (CPAP) for the treatment of obstructive sleep apnea syndrome. Therefore, we studied the effects of postural changes and of the use of nasal CPAP. The EIT revealed heterogeneous distribution of regional lung ventilation, the ventilation being higher in the right lung, and this distribution was influenced by postural changes and CPAP use. The EIT assessment of regional lung ventilation produced results similar to those obtained with the radionuclide imaging technique and had the advantage of providing a dynamic evaluation without radiation exposure.

Stenosis or hyperperfusion in sickle cell disease--ultrasound assessment of cerebral blood flow volume.

Increased blood flow velocity (BFV) in basal cerebral arteries measured by transcranial color-coded sonography (TCCS) is a stroke risk factor in sickle cell disease (SCD). Raised BFV may be caused by vessel narrowing or by hyperperfusion. In 44 SCD patients and 14 controls, intracranial arterial BFVs and global cerebral blood flow (CBF) were analyzed by TCCS and extracranial duplex ultrasound, respectively. Magnetic resonance imaging and magnetic resonance angiography were performed in all patients with pathologic intracranial BFV rise. Intracranial BFVs and CBF in SCD were significantly higher than in controls. CBF in SCD correlated with BFV in all intracranial arteries and correlated inversely with age and hemoglobin values. Magnetic resonance angiography failed to demonstrate any stenosis in our SCD patients, thus raised intracranial BFVs must be interpreted as an anemia-dependent cerebral hyperperfusion. These findings suggest that the pathomechanism of stenosis-derived arterio-arterial embolism might be less relevant in SCD-related ischemic stroke, and other factors like small vessel disease or sickle cell-induced microvascular blood clotting have to be considered.

Assessment and prevention of exercise-induced bronchoconstriction.

The assessment of exercise-induced bronchoconstriction (EIB) in athletes requires the measurement of forced expiratory volume in 1 s (FEV(1)) before and after vigorous exercise or a surrogate of exercise such as eucapnic voluntary hyperpnoea (EVH) of dry air or mannitol dry powder. Exercise testing in a laboratory has a low sensitivity to identify EIB, and exercise testing in the field can be a challenge in itself particularly in cold weather athletes. The EVH test requires the subject to ventilate dry air containing ∼5% CO(2) for 6 min through a low-resistance circuit at a rate higher than that usually achieved on maximum exercise. A ≥10% reduction in FEV(1) is a positive response to exercise and EVH and, when sustained, is usually associated with release of inflammatory mediators of broncho constriction. Another surrogate, mannitol dry powder, given by inhalation in progressively increasing doses, is used to mimic the dehydrating stimulus of exercise hyperpnoea. A positive mannitol test is a 15% fall in FEV(1) at ≤635 mg and reveals potential for EIB. Mannitol has a high specificity for identifying a clinical diagnosis of asthma. Once a diagnosis of EIB is established, the athlete needs to know how to avoid EIB. Being treated daily with an inhaled corticosteroid to reduce airway inflammation, inhaling a ß(2) agonist or a cromone immediately before exercise, or taking a leukotriene antagonist several hours before exercise, all inhibit or prevent EIB. Other strategies include warming up prior to exercise and reducing respiratory water and heat loss by using face masks or nasal breathing.

The effects of stenosis severity on the hemodynamic parameters-assessment of the correlation between stress phase angle and wall shear stress.

To study the effects of increase in the degree of stenosis severity and subsequent complexity of hemodynamic patterns on hemodynamic parameters, experimental investigations and numerical simulations were performed. The correlations between the large negative Stress Phase Angle (SPA), the low mean Wall Shear Stress (WSS) and high Oscillatory Shear Index (OSI) were investigated at the distal shoulder and post-stenotic regions as the outcomes of elevated stenosis severity. Models included non-Newtonian fluid flow in stenotic arteries with 30-80% symmetrical stenoses. To study the interactions between pulsatile WSS and pulsatile wall circumferential stress (WCS) acting on endothelial cells, SPA as the phase difference between WSS and WCS waves was used. Moreover, the distribution of SPA on the lumen axis was compared to the distributions of the mean WSS and OSI that have been regarded until now as the determinants of atherosclerosis-prone regions. Results indicate that an increase in stenosis severity, not only affects the mean WSS, mean WCS and pulse amplitudes, but also influences the phase difference between them. The SPA is large negative on the distal shoulder and post-stenotic areas where atherosclerotic plaque develops. The increasing stenosis severity and the subsequent increasing complexity of hemodynamic patterns affect the correlation between any of the low mean WSS and high OSI with large negative SPA, such that it not only leads to create and develop some regions where the correlation between any of the low mean WSS and high OSI with large negative SPA is well but also leads to create and develop other regions where such correlations fail.

Colonic stents: the modern treatment of colonic obstruction.

Colonic stents traditionally have been used for the management of colorectal cancer, either as a palliative treatment or as a bridge to surgery. More recently, colonic stents have also been advocated as part of the therapy of benign strictures. A number of colonic stents are available worldwide, four of which are made in the USA. These stents are classified as covered or uncovered, with similar clinical applications. Technical and clinical success rates are similar among these different stents, as well as the rate of complications, which mainly consist of obstruction and migration. The deployment systems utilize fluoroscopy, endoscopy, or both. More recently, stents became available that are deployed "through the scope" (TTS) making the procedure faster. However, this advance does not exclude the use of fluoroscopy, particularly in those cases where the direct visualization of the proximal end of the stricture is absent. The increasing experience in the management of colorectal cancer with colonic stents decreases the morbidity and mortality, as well as cost, in comparison with surgical intervention for acute colonic obstruction. Management with colonic stents can also rule out proximal synchronous lesions after initial decompression prior to definitive surgery. Benign conditions may also be treated with stents. A multidisciplinary approach for the use of colonic stents during assessment and management of acute colonic obstruction is necessary in order to achieve a satisfactory outcome, whether that be better quality of life or improved survival.

Numerical modeling of stress in stenotic arteries with microcalcifications: a parameter sensitivity study.

As a follow-up to the work presented in Wenk et al. (2010, "Numerical Modeling of Stress in Stenotic Arteries With Microcalcifications: A Micromechanical Approximation," ASME J. Biomech. Eng., 132, p. 091011), a formal sensitivity study was conducted in which several model parameters were varied. The previous work only simulated a few combinations of the parameters. In the present study, the fibrous cap thickness, longitudinal position of the region of microcalcifications, and volume fraction of microcalcifications were varied over a broader range of values. The goal of the present work is to investigate the effects of localized regions of microcalcifications on the stress field of atherosclerotic plaque caps in a section of carotid artery. More specifically, the variations in the magnitude and location of the maximum circumferential stress were assessed for a range of parameters using a global sensitivity analysis method known as Sobol' indices. The stress was calculated by performing finite element simulations of three-dimensional fluid-structure interaction models, while the sensitivity indices were computed using a Monte Carlo scheme. The results indicate that cap thickness plays a significant role in the variation in the magnitude of the maximum circumferential stress, with the sensitivity to volume fraction increasing when the region of microcalcification is located at the shoulder. However, the volume fraction played a larger role in the variation in the location of the maximum circumferential stress. This matches the finding of the previous study (Wenk et al., 2010, "Numerical Modeling of Stress in Stenotic Arteries With Microcalcifications: A Micromechanical Approximation," ASME J. Biomech. Eng., 132, p. 091011), which indicates that the maximum circumferential stress always shifts to the region of microcalcification.

Evaluation of a milk-flow assessment technique in dairy cows with normal teat canals or stenotic teat canals.

OBJECTIVE: To assess the usefulness and reliability of a milk-flow measurement technique and the values obtained in unobstructed teats and teats with teat canal stenosis in dairy cows. ANIMALS: 16 Holstein cows. PROCEDURES: Teats were assessed via hand milking and classified as unobstructed or partially obstructed. Partially obstructed teats were further categorized according to the anatomic location of the obstruction via ultrasonography into teat canal obstruction (TCO) and obstruction at the proximal portion of the teat canal (Fürstenberg rosette obstruction [FRO]) The milk-flow characteristics of the teat canal were assessed by measuring the intracisternal pressure at the start (PSL) and at cessation (PCL) of leakage of an infused solution. RESULTS: The PSL and PCL values among unobstructed teats were not significantly different between lactating and nonlactating cows nor among quarters. In assessment of test-retest intrarater reliability, a high degree of correlation was detected for PSL (correlation coefficient, 0.94; 95% confidence interval, 0.90 to 0.96) and PCL (correlation coefficient, 0.92; 95% confidence interval, 0.86 to 0.95). Teats with TCO and FRO had higher PSL and PCL values, compared with unobstructed teats. Teats with FRO had significantly higher PSL but lower PCL than teats with TCO. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated the usefulness and reliability of the technique in assessing the milk-flow characteristics of the teat canal. The milk-flow pattern of teats with teat canal stenosis varies depending on the location of obstruction. This technique may be a valuable tool in evaluating the effectiveness of teat canal surgery.

Real-time hemodynamic assessment of downstream effects of intracranial stenoses in patients with orthostatic hypoperfusion syndrome.

BACKGROUND: Arterial flow velocity changes on transcranial Doppler can reflect changes in cerebral flow during position-induced ischemia if obtained during short-term monitoring of positional changes. SUBJECTS AND METHODS: Our multicenter group monitored symptomatic and asymptomatic arteries in patients with recurrent neurological deficits during positional changes and documented intracranial arterial stenosis. Bilateral posterior cerebral and middle cerebral arteries were monitored dependent on clinical symptom localization. The symptomatic artery was monitored distal to the intracranial stenosis, and mean flow velocities (MFV) were recorded at different body positions. The symptomatic artery relative MFV ratio was defined as the ratio of symptomatic artery MFV in the asymptomatic position--MFV in the symptomatic position/MFV in the asymptomatic position. RESULTS: Sixteen patients underwent transcranial Doppler monitoring: mean age 62 +/- 19 years, 11 (69%) men, 6 (40%) with transient ischemic attacks. Ten patients (63%) had posterior and 6 anterior circulation symptoms. Patients developed neurological symptoms while standing up (63%) and/or sitting (44%), walking (13%) or during neck extension (6%). Symptomatic artery MFV dropped by > or =25% from the resting to the symptomatic position in all patients except for one. The mean symptomatic artery MFV relative ratio was higher compared with the mean asymptomatic artery MFV relative ratio: 0.5 +/- 0.28 versus -0.02 +/- 0.1 (p = 0.001, Wilcoxon test). The symptomatic artery relative ratio of >0.25 had a 94% sensitivity and 100% specificity for predicting neurological symptom development during testing (kappa = 0.9, p < 0.001). CONCLUSIONS: A significant reduction in intracranial flow velocity distal to an intracranial stenosis can identify patients whose symptoms can worsen with positional changes. These patients may prove a target for interventional revascularization techniques.