ABSTRACT
ABSTRACT Background: Cerebral autoregulation (CA) is the ability of intracranial vessels to maintain a constant cerebral blood flow (CBF) during changes of cerebral perfusion pressure (CPP) related to fluctuations in blood pressure, postural changes or increased metabolic demands. It has been suggested that individuals with silent cerebral small vessel disease (SVD) may have impaired CA, but information is inconclusive. We describe the protocol of a study aimed to assess the association between white matter hyperintensities (WMH) of presumed vascular origin and poor dynamic CA, and to determine the effects of head-up and body positioning in patients with this condition. Methods: Using a case-control study design, we will assess the relationship between severity of WMH and dynamic CA, measured by continuous transcranial Doppler assessment of CBF velocities in the middle cerebral arteries (MCAs) combined with beat-to-beat blood pressure monitoring. Dynamic CA will be analyzed by calculating the mean flow index as the ratio of median arterial pressure and mean flow velocities of the MCAs. Participants will be categorized as case-patients if the MRI shows moderate-to-severe WMH. For every case-patient, an age- and sex-matched healthy individual with no neuroimaging evidence of SVD will be selected as a control. Comment: This study will assess whether head-up and body positioning impairs dynamic CA in the setting of diffuse subcortical damage related to SVD, providing further evidence on the importance of CPP in maintaining the CBF. If positive, the study will provide evidence favoring the stop of aggressive hypertensive therapy or interventions promoting orthostatic hypotension to reduce the risk of further ischemic brain damage in these cases.
RESUMEN Antecedentes: La autorregulación cerebral (CA) es la capacidad de los vasos cerebrales de mantener un flujo sanguíneo constante durante cambios en la presión de perfusión cerebral (PPC) relacionados con fluctuaciones de la presión arterial, cambios posturales o aumento de las demandas metabólicas. Se ha sugerido que las personas con enfermedad de pequeño vaso cerebral pueden tener CA deteriorada, pero la información no es concluyente. Describimos el protocolo de un estudio cuyo objetivo es evaluar la asociación entre hiperintensidades de substancia blanca y CA dinámica deficiente, para determinar los efectos del posicionamiento de cabeza y cuerpo en estos pacientes. Métodos: Utilizando un diseño de caso-control, evaluaremos la relación entre la severidad de las hiperintensidades de substancia blanca y la CA dinámica, mediante Doppler transcraneal continuo de las velocidades de flujo en las arterias cerebrales medias (ACM) combinadas con monitoreo de la presión arterial. La CA dinámica se analizará calculando el índice de flujo medio y la relación entre la presión arterial media y las velocidades medias de flujo de las ACM. Los participantes se clasificarán como casos si la IRM muestra hiperintensidades de substancia blanca. Para cada caso, se seleccionará a un individuo sin evidencia de enfermedad de pequeño vaso como control. Comentario: Este estudio evaluará si el posicionamiento de la cabeza hacia arriba afecta la CA dinámica en el contexto del daño subcortical difuso relacionado con enfermedad de pequeño vaso, proporcionando evidencia adicional sobre la importancia de la PPC en el mantenimiento del flujo en estos sujetos. El estudio proporcionará evidencia sobre el uso de terapia hipertensiva agresiva o intervenciones que promueven la hipotensión ortostática para reducir el riesgo de daño cerebral isquémico.
ABSTRACT
The carotid intima media thickness (cIMT) is a predictor of cardiovascular events. The neck circumference (NC) has been investigated as a risk factor for increased cIMT with contradictory results. This study assessed the relationship between NC and cIMT in Atahualpa residents aged ≥40 years who had sonographic examination of carotid arteries (n = 590). We also discussed on potential pathogenetic mechanisms underlying this association. Participants belonged to the Native Ecuadorian (Amerindians) ethnic group. Non-parametric regression models were used to assess the aforementioned relationship, after adjusting for relevant confounders. The mean age of participants was 60.9 ± 12.7 years (58% women). The mean value of the cIMT was 0.85 ± 0.19 mm. The mean NC was 35.8 ± 34 cm. The NC was normally distributed, but the cIMT was not. Mean values of NC and cIMT were significantly greater in men than in women. Non-parametric models showed significant differences in median cIMT values according to quartiles of NC. Predictive cIMT margins increased by quartiles of NC, significantly among individuals in the 1st quartile as compared to the 3rd quartile. In this population of Amerindians, smaller NC is associated with lower values of cIMT. The pattern of this association is different in men than in women. Sex-related differences in cervical fat tissue distribution probably accounted for such differences.
ABSTRACT
BACKGROUND: No information is available on the distribution of cervicocephalic atherosclerosis in Amerindians. We aimed to assess the distribution of these lesions and their correlation with cardiovascular risk factors in Amerindians living in rural Ecuador. METHODS: Atahualpa residents aged ≥40years underwent head CT for assessment of carotid siphon calcifications (CSC) and sonographic examination for measurement of the carotid intima media thickness (cIMT). CSC were used as a surrogate of intracranial atherosclerosis and the cIMT as a surrogate of extracranial atherosclerosis. Linear regression and multinomial logistic regression models were fitted to assess the association between cIMT and CSC, and to evaluate differences in risk factors across individuals with atherosclerosis involving both arterial beds when compared with those with extra- or intracranial atherosclerosis alone, or no atherosclerosis. RESULTS: Of 590 participants, 145 had high calcium content in the carotid siphons and 87 had a cIMT >1mm (25% versus 15%, P < .001). Thirty-eight (7%) individuals had atherosclerosis at both vascular beds, 107 (18%) had intracranial atherosclerosis, and 49 (8%) had extracranial atherosclerosis alone. The cIMT and CSC were independently associated (P = .008). When compared with participants without atherosclerosis, those with atherosclerosis at both vascular beds were older, more often male, hypertensive and diabetic. Subjects with intracranial atherosclerosis alone were older, and those with extracranial atherosclerosis alone reported less physical activity than those without atherosclerosis. CONCLUSION: Intracranial atherosclerosis is more common than extracranial atherosclerosis in Amerindians. Traditional risk factors only explain a minority of cases of cervicocephalic atherosclerosis in this population.
Subject(s)
Carotid Artery Diseases/ethnology , Indians, South American , Intracranial Arteriosclerosis/ethnology , Rural Health/ethnology , Aged , Carotid Artery Diseases/diagnostic imaging , Carotid Intima-Media Thickness , Chi-Square Distribution , Ecuador/epidemiology , Female , Humans , Intracranial Arteriosclerosis/diagnostic imaging , Linear Models , Logistic Models , Male , Middle Aged , Multidetector Computed Tomography , Multivariate Analysis , Odds Ratio , Plaque, Atherosclerotic , Risk Factors , Vascular Calcification/diagnostic imaging , Vascular Calcification/ethnologyABSTRACT
RESUMEN El diagnóstico de muchas de las enfermedades neurológicas no transmisibles requiere de la práctica de una resonancia magnética, la cual no se encuentra disponible en regiones rurales o remotas. Es importante realizar esfuerzos destinados a encontrar pruebas diagnósticas portátiles que sirvan como tamizaje para la identificación de personas que necesitan ser sometidas a una IRM. Como parte del Proyecto Atahualpa, hemos invitado a todos los participantes ≥60 años para la práctica de una IRM de cerebro y aproximadamente el 80% de las personas han aceptado el procedimiento. Por lo tanto, tenemos la oportunidad única de probar la validez de pruebas no-invasivas que puedan ser utilizadas como substitutos de resonancia para identificar candidatos a hacerse dicho examen. Hasta la fecha, hemos estudiado el valor del índice tobillo-brazo, la confiabilidad de la relación neutrófilos-linfocitos, la exactitud de la presencia de retinopatía hipertensiva y el valor del Doppler transcraneal para la detección de personas con enfermedad de pequeño vaso cerebral. Los individuos con índice tobillo-brazo anormal tiene 4 veces más riesgo de tener un infarto lacunar silente que aquellos con índice normal. Una relación neutrófilos-linfocitos elevada es pobremente sensitiva pero altamente específica para detectar personas con por lo menos un marcador de imagen de enfermedad de pequeño vaso. Los individuos con retinopatía hipertensiva Grados 2-3 tienen casi 4 veces más riesgo de tener hiperintensidades de sustancia blanca que aquellos con retinopatía Grado 1 o sin retinopatía. Finalmente, la correlación del índice de pulsatilidad de las arterias intracraneales para detectar marcadores de enfermedad de pequeño vaso es pobre. Seguimos en la búsqueda de una prueba económica y confiable que permita la identificación de sujetos aparentemente sanos, con riesgo de desarrollar eventos cerebrovasculares catastróficos.
ABSTRACT Diagnosis of many non-communicable neurological diseases require the use of MRI, which is not readily available in remote rural populations. Efforts should be directed to find portable screening diagnostic tools that may help identify candidates for MRI screening. In the Atahualpa Project, all participants aged ≥60 years have been invited for the practice of MRI, and about 80% of them have underwent the procedure. Therefore, we have the unique opportunity to test the accuracy of non-invasive exams to be used as surrogates to MRI for identifying candidates for the practice of this exam. To date, we have assessed the value of the ankle-brachial index ABI), the reliability of the neutrophil-to-lymphocyte ratio (NLR), the accuracy of hypertensive retinopathy, and the value of transcranial Doppler (TCD) to detect individuals with cerebral small vessel disease. Individuals with an abnormal ABI have 4 times de odds of having a silent lacunar infarct than those with a normal ABI. A high NLR has a poor sensitivity but is highly specific for detecting persons with at least one imaging signature of small vessel disease. Individuals with hypertensive retinopathy Grades 2-3 are almost four times more likely to have moderate-to-severe white matter hyperintensities than those with no- or only Grade 1 retinopathy. Finally, the correlation between the pulsatility indexes of major cerebral arteries with imaging markers of small vessel disease, as assessed by TCD, was poor. We are still in the search of some non-expensive and readily available biomarker that allow the identification of apparently healthy persons at risk of suffering a catastrophic cerebrovascular event.
ABSTRACT
PURPOSE: To assess the role of temporal bone characteristics in transcranial Doppler (TCD) insonation failures in Amerindians living in rural Ecuador. METHODS: We evaluated thickness and texture of temporal bones in community-dwelling Amerindians ≥65 years old undergoing TCD. Using receiver operator characteristics curve analysis and generalized estimating equations, we investigated factors associated with insonation failures. RESULTS: Of 65 participants (mean age 74.7 ± 6.7 years, 60% women), 32 (49%) had uni- or bilateral insonation failure through temporal windows. Considering temporal bones independently, 57 of 130 (44%) had poor insonation. Mean thickness was higher (4.7 ± 1.2 versus 2.7 ± 0.9, p < 0.0001), and texture more often heterogeneous (93% versus 22%, p < 0.0001) in bones with poor acoustic windows. Thickness, better predicting poor insonation, was ≥3.6 mm if used alone, and ≥2.7 mm if used together with heterogeneous texture. For every millimeter of increase in thickness, subjects were 2.9 times more likely to have insonation failures. Per se, heterogeneous texture increased by 3.2 times the odds for poor insonation. In all models, being woman increased the odds for poor insonation by six to nine times. CONCLUSIONS: Temporal bone thickness and texture are independent predictors of TCD insonation failure in Amerindians.
Subject(s)
Bone Density , Indians, Central American/ethnology , Temporal Bone/diagnostic imaging , Ultrasonography, Doppler, Transcranial , Aged , Aged, 80 and over , Ecuador/ethnology , Female , Humans , Male , ROC Curve , Research Design , Sex Factors , Temporal Bone/chemistryABSTRACT
BACKGROUND: In a population-based sampling study conducted in community-dwelling older adults living in rural Ecuador, we aimed to assess the relation among sleep-disordered breathing, cerebral pulsatility index, and diffuse small vessel disease. METHODS: Of 25 participants, 9 (36%) had moderate-to-severe sleep-disordered breathing, characterized by an apnea/hypopnea index ≥15 per hour, and 10 (40%) had moderate-to-severe white matter hyperintensities, graded according to the modified Fazekas scale. Mean (SD) pulsatility index in the middle cerebral artery was 1.18 (0.19) and positively correlated with the apnea/hypopnea index (R = .445, P = .03, [Pearson's correlation coefficient]). The middle cerebral artery pulsatility index was increased in persons with moderate-to-severe sleep-disordered breathing compared with persons who had none-to-mild sleep-disordered breathing (mean [SD] 1.11 [0.12] vs. 1.3 [0.23], P = .01). No significant differences were found in the prevalence of moderate-to-severe white matter hyperintensities across groups of sleep-disordered breathing (P = .40) or in the mean apnea/hypopnea index across groups of persons with none-to-mild or moderate-to-severe white matter hyperintensities (P = .16). CONCLUSIONS: This pilot study shows that moderate-to-severe sleep-disordered breathing correlates with cerebral pulsatility, but such association might be independent of diffuse small vessel disease.
Subject(s)
Cerebrum/physiopathology , Pulsatile Flow , Respiration , Sleep Wake Disorders/physiopathology , Aged , Cerebrum/blood supply , Female , Humans , Magnetic Resonance Imaging , Male , Pilot Projects , Ultrasonography, Doppler, TranscranialABSTRACT
BACKGROUND: Diagnosis of cerebral small vessel disease (SVD) is a challenge in remote areas where magnetic resonance imaging (MRI) is not available. Hospital-based studies in high-risk or stroke patients have found an association between the pulsatility index (PI) of intracranial arteries - as derived from transcranial Doppler (TCD) - and white matter hyperintensities (WMH) of presumed vascular origin. We aimed to assess the reliability of cerebral pulsatility indices to identify candidates for MRI screening in population-based studies assessing prevalence of SVD. METHODS: A representative sample of stroke-free Atahualpa residents aged ≥65 years investigated with MRI underwent TCD. Using generalized linear models, we evaluated whether the PI of major intracranial arteries correlate with WMH (used as a proxy of diffuse SVD), after adjusting for demographics and cardiovascular risk factors. RESULTS: Out of 70 participants (mean age 70.6 ± 4.6 years, 57% women), 28 (40%) had moderate-to-severe WMH. In multivariate models, there were no differences across categories of WMH in the mean PI of middle cerebral arteries (1.10 ± 0.16 vs. 1.22 ± 0.24, ß: 0.065, 95% confidence interval (CI): -0.084-0.177, P = 0.474) or vertebrobasilar arteries (1.11 ± 0.16 vs. 1.29 ± 0.27, ß: 0.066, 95% CI: -0.0024-0.156, P = 0.146). CONCLUSIONS: Cerebral PI should not be used to identify candidates for MRI screening in population-based studies assessing the burden of SVD.
ABSTRACT
BACKGROUND: There is no information on transcranial Doppler (TCD) failures due to poor insonation among native inhabitants of Latin America. METHODS: Seventy Ecuadorian natives and 70 age- and sex-matched individuals of European origin underwent TCD. The same investigators performed all exams using the same equipment and protocol. Using the McNemar's test for correlated proportions, we compared TCD failures related to poor insonation across ethnic groups. RESULTS: Out of 140 participants, 56 (40%) had one or more suboptimal/absent acoustic windows. These persons were older (p = 0.01) and were more often women (p < 0.0001) than those with all optimal windows (irrespective of race/ethnicity). In the matched-pair analysis, Amerindians were more likely to have suboptimal/absent acoustic windows than individuals of European origin (OR: 2.8, 95% CI: 1.3-6.5, p = 0.006). CONCLUSION: Amerindians are almost three times more likely to have insonation failures related to poor acoustic windows than their European counterparts.
