Blood-brain barrier integrity is linked to cognitive function, but not to cerebral arterial pulsatility, among elderly.

Blood-brain barrier (BBB) disruption may contribute to cognitive decline, but questions remain whether this association is more pronounced for certain brain regions, such as the hippocampus, or represents a whole-brain mechanism. Further, whether human BBB leakage is triggered by excessive vascular pulsatility, as suggested by animal studies, remains unknown. In a prospective cohort (N = 50; 68-84 years), we used contrast-enhanced MRI to estimate the permeability-surface area product (PS) and fractional plasma volume ( v p ), and 4D flow MRI to assess cerebral arterial pulsatility. Cognition was assessed by the Montreal Cognitive Assessment (MoCA) score. We hypothesized that high PS would be associated with high arterial pulsatility, and that links to cognition would be specific to hippocampal PS. For 15 brain regions, PS ranged from 0.38 to 0.85 (·10-3 min-1) and v p from 0.79 to 1.78%. Cognition was related to PS (·10-3 min-1) in hippocampus (ß = - 2.9; p = 0.006), basal ganglia (ß = - 2.3; p = 0.04), white matter (ß = - 2.6; p = 0.04), whole-brain (ß = - 2.7; p = 0.04) and borderline-related for cortex (ß = - 2.7; p = 0.076). Pulsatility was unrelated to PS for all regions (p > 0.19). Our findings suggest PS-cognition links mainly reflect a whole-brain phenomenon with only slightly more pronounced links for the hippocampus, and provide no evidence of excessive pulsatility as a trigger of BBB disruption.

Arterial pulsation dependence of perivascular cerebrospinal fluid flow measured by dynamic diffusion tensor imaging in the human brain.

Perivascular cerebrospinal fluid (pCSF) flow is a key component of the glymphatic system. Arterial pulsation has been proposed as the main driving force of pCSF influx along the superficial and penetrating arteries; however, evidence of this mechanism in humans is limited. We proposed an experimental framework of dynamic diffusion tensor imaging with low b-values and ultra-long echo time (dynDTIlow-b) to capture pCSF flow properties during the cardiac cycle in human brains. Healthy adult volunteers (aged 17-28 years; seven men, one woman) underwent dynDTIlow-b using a 3T scanner (MAGNETOM Prisma, Siemens Healthcare, Erlangen, Germany) with simultaneously recorded cardiac output. The results showed that diffusion tensors reconstructed from pCSF were mainly oriented in the direction of the neighboring arterial flow. When switching from vasoconstriction to vasodilation, the axial and radial diffusivities of the pCSF increased by 5.7 % and 4.94 %, respectively, suggesting that arterial pulsation alters the pCSF flow both parallel and perpendicular to the arterial wall. DynDTIlow-b signal intensity at b=0 s/mm2 (i.e., T2-weighted, [S(b=0 s/mm2)]) decreased in systole, but this change was ∼7.5 % of a cardiac cycle slower than the changes in apparent diffusivity, suggesting that changes in S(b=0 s/mm2) and apparent diffusivity arise from distinct physiological processes and potential biomarkers associated with perivascular space volume and pCSF flow, respectively. Additionally, the mean diffusivities of white matter showed cardiac-cycle dependencies similar to pCSF, although a delay relative to the peak time of apparent diffusivity in pCSF was present, suggesting that dynDTIlow-b could potentially reveal the dynamics of magnetic resonance imaging-invisible pCSF surrounding small arteries and arterioles in white matter; this delay may result from pulse wave propagation along penetrating arteries. In conclusion, the vasodilation-induced increases in axial and radial diffusivities of pCSF and mean diffusivities of white matter are consistent with the notion that arterial pulsation can accelerate pCSF flow in human brain. Furthermore, the proposed dynDTIlow-b technique can capture various pCSF dynamics in artery pulsation.

Direct angiographic comparison of different velocity-selective saturation, inversion, and DANTE labeling modules on cerebral arteries.

PURPOSE: This study evaluated the velocity-selective (VS) MRA with different VS labeling modules, including double refocused hyperbolic tangent, eight-segment B1-insensitive rotation, delay alternating with nutation for tailored excitation, Fourier transform-based VS saturation, and Fourier transform-based inversion. METHODS: These five VS labeling modules were evaluated first through Bloch simulations, and then using VSMRA directly on various cerebral arteries of healthy subjects. The relative signal ratios from arterial ROIs and surrounding tissues as well as relative arteria-tissue contrast ratios of different methods were compared. RESULTS: Double refocused hyperbolic tangent and eight-segment B1-insensitive rotation showed very similar labeling effects. Delay alternating with nutation for tailored excitation yielded high arterial signal but with residual tissue signal due to the spatial banding effect. Fourier transform-based VS saturation with half the time of other techniques serves as an efficient nonsubtractive VSMRA method, but the remaining tissue signal still obscured some small distal arteries that were delineated by other subtraction-based VSMRA, allowing more complete cancelation of static tissue. Fourier transform-based inversion produced the highest arterial signal in VSMRA with minimal tissue background. CONCLUSION: This is the first study that angiographically compared five different VS labeling modules. Their labeling characteristics on arteries and tissue and implications for VSMRA and VS arterial spin labeling are discussed.

Assessment of arterial pulsatility of cerebral perforating arteries using 7T high-resolution dual-VENC phase-contrast MRI.

PURPOSE: Directly imaging the function of cerebral perforating arteries could provide valuable insight into the pathology of cerebral small vessel diseases (cSVD). Arterial pulsatility has been identified as a useful biomarker for assessing vascular dysfunction. In this study, we investigate the feasibility and reliability of using dual velocity encoding (VENC) phase-contrast MRI (PC-MRI) to measure the pulsatility of cerebral perforating arteries at 7 T. METHODS: Twenty participants, including 12 young volunteers and 8 elder adults, underwent high-resolution 2D PC-MRI scans with VENCs of 20 cm/s and 40 cm/s at 7T. The sensitivity of perforator detection and the reliability of pulsatility measurement of cerebral perforating arteries using dual-VENC PC-MRI were evaluated by comparison with the single-VENC data. The effects of temporal resolution in the PC-MRI acquisition and aging on the pulsatility measurements were investigated. RESULTS: Compared to the single VENCs, dual-VENC PC-MRI provided improved sensitivity of perforator detection and more reliable pulsatility measurements. Temporal resolution impacted the pulsatility measurements, as decreasing temporal resolution led to an underestimation of pulsatility. Elderly adults had elevated pulsatility in cerebral perforating arteries compared to young adults, but there was no difference in the number of detected perforators between the two age groups. CONCLUSION: Dual-VENC PC-MRI is a reliable imaging method for the assessment of pulsatility of cerebral perforating arteries, which could be useful as a potential imaging biomarker of aging and cSVD.

Systematization of the brain base arteries in ostrich (Struthio camelus)

Thirty ostrich (Struthio camelus) brains were used, injected with latex, to describe the arteries of the brain base.The largest occurrences of the arteries were: The cerebral carotid artery (100%), the intercarotid anastomosis(100%). The caudal branch of the cerebral carotid artery was, on the right (R), developed (53.3%) and vestigial(46.7%); on the left (L), developed (66.7%) and vestigial (33.3%). The ventral tectal mesencephalic artery onthe R (53.3%), on the L (66.7%), direct branch of the cerebral carotid artery on the R (43.3%), on the L (30%)and, direct branch of the basilar artery (3.3%) in both antimeres. The basilar artery was a single vessel (80%),double in (13.3%) and “in island” formation (6.7%). The caudal ventral cerebellar artery was single (96.7%),double (3.3%) on the R and, single (93.3%), double (6.7%) on the L. The dorsal spinal artery was a collateralbranch of the caudal ventral cerebellar artery on the R (96.7%), on the L (93.3%). The ventral spinal artery wasdouble (90%) and single (10%). The rostral branch of the cerebral carotid artery (100%). The caudal cerebralartery, on the R, was double (90%) and single (10%); on the L, was double (53.3%) and single (46.7%). Themiddle cerebral artery was a single vessel (100%). The cerebroethmoidal artery was single (100%). The rostralcerebral artery was single (90%), double (10%) on the R and single (96.7%), double (3.3%) on the L. Thecerebral arterial circle was rostrally open (100%) and, caudally, open (80%) and closed (20%).

Systematization, distribuiton and Territory of the rostral cerebral artery on the brain surface in chinchilla

The present study has analyzed thirty chinchilla (Chinchilla lanigera) brains, injected with latex, aiming tosystematize and describe the distribution and the vascularization territories of the rostral cerebral artery. Therostral cerebral artery was the terminal branch of the terminal branch, right and left, of the basilar artery,projected from the emittion of the middle cerebral artery, rostromedially, crossing dorsally the optic nerve untilit reaches the cerebral longitudinal fissure, ventrally. Its branches were distributed mostly on the paleopallium,supplying the olfactory trigone, the medial olfactory tract, the olfactory peduncle and the olfactory bulb.The branches to the neopallium vascularized the entire medial surface, except for the tenctorial part of it, thefrontal pole and a zone that was extended from the frontal to the occipital poles, medially to the vallecula,on the convex surface of the cerebral hemisphere. The first collateral branch of the rostral cerebral artery wasthe medial branch, which entered into the longitudinal fissure of the brain and continued as rostral interhemisphericartery. The rostral cerebral artery continued rostrally emitting central branches and the medialand lateral arteries of the olfactory bulb, to the paleopallial region of the chinchilla brain. After the emittion ofthe medial artery of the olfactory bulb, the rostral cerebral artery continued to follow the cerebral longitudinalfissure, as internal ethmoidal artery, its terminal branch.

Doppler transcraniano convencional em voluntários assintomáticos: variabilidade e valores de referência para parâmetros de fluxo sanguíneo / Reference values for measures of blood flow velocities and impedance indexes in healthy individuals through conventional transcranial Doppler

OBJETIVO: Estabelecer valores de referência para medidas de velocidade sanguínea e índices de impedância em indivíduos saudáveis por meio do Doppler transcraniano convencional (DTC) e observar suas variações em relação à idade e sexo. MÉTODO: Foram examinados 88 voluntários assintomáticos, sem antecedentes de doença cerebrovascular, cardíaca ou vascular periférica. Os exames de DTC foram realizados pelo mesmo examinador, sendo as artérias cerebrais médias, anteriores e posteriores estudadas por meio da janela temporal e as artérias vertebrais e basilar por meio da janela suboccipital. Foram arquivados os valores de velocidade média (VM), velocidade de pico sistólico (VPS), velocidade diastólica final (VDF) e índices de resistência (IR) e pulsatilidade (IP) de cada segmento arterial examinado. RESULTADOS: Os limites de referência encontrados por nós foram semelhantes aos descritos por outros autores para todos os parâmetros estudados. Houve tendência das velocidades de fluxo diminuírem e dos índices de impedância aumentarem com o avançar da idade. Os valores de velocidade nas mulheres foram superiores aos encontrados em homens. CONCLUSÃO: O DTC se mostrou útil na avaliação hemodinâmica cerebral de nossa população. Os nossos resultados são semelhantes aos de outros estudos, tanto nos valores de referência quanto na sua relação com a idade e o sexo.

OBJECTIVE: To establish reference values for measures of blood flow velocities and impedance indexes in healthy individuals through conventional transcranial Doppler (TCD) and to observe their variations in relation to the age and sex. METHOD: 88 asymptomatic volunteers were examined without antecedents of cardiac, peripheral or cerebrovascular diseases. The TCD were accomplished by the same examiner. The middle, anterior and posterior cerebral arteries were studied through the temporal acoustic window and the vertebral and basilar arteries through the suboccipital acoustic window. The values of mean velocity (MV), peak-systolic velocity (PSV), final diastolic velocity (FDV), resistance index (RI) and pulsatility index (PI) of each examined arterial segment were filed. RESULTS: The reference limits found by us were similar to the described by other authors for all of the studied parameters. There was tendency of the flow velocities decrease and of the impedance indexes increase with moving forward of the age. The values of velocities in the women were superior to the found in men. CONCLUSION: TCD was shown useful in the evaluation of hemodynamic cerebral for our population. Our results are similar to the other studies, so much in the reference values as in relationship with the age and the sex.

A systematic study of the brain base arteries and their blood supply sources in the chinchilla (Chinchilla lanigera - Molina 1782)

The origin of the blood supply to the brain and arteries of the ventral surface of the brain was studied in 31 adult chinchillas (Chinchilla lanigera). The arterial system was filled with latex 603 via the brachioencephalic trunk and the left subclavian artery, both of which arose from the aortic arch in most cases. The right and left internal carotid arteries (100% and 93.3%, respectively) did not contribute to the brain supply. The vertebral arteries were present in all cases and formed the basilar artery (96.7%) that gave off the ventral spinal artery caudally in all cases. The caudal cerebellar artery was single (80%) or double (20%) on the right, and single (70%) or double (30%) on the left. The rostral cerebellar artery was present as a caudal vessel on the right (73.3%) and on the left (70%), and as a rostral vessel in all cases. The rostral tectal artery was single in all cases. The caudal cerebral artery was single (53.3%), double (36.7%) or triple (10%) on the right, and single (46.7%), double (46.7%) or triple (6.7%) on the left. The hypophyseal artery was present in all cases. The internal ophthalmic artery was present only on the right (26.7%), or only on the left (23.3%). The middle cerebral artery was single in all cases on both sides. The rostral cerebral artery was present as a well-developed (96.7%) or vestigial (3.3%) vessel in both antimeres, gave off lateral arteries to the olfactory bulb and the median rostral inter-hemispheric artery, and ended as the internal ethmoidal artery. The cerebral arterial circle was open (70%) or closed (30%) rostrally, and closed caudally in all cases. The brain was supplied almost exclusively by the vertebral-basilar system.

Anatomy of the caudal cerebral artery on the surface of opossum brain (Didelphis albiventris)

The anatomy of the caudal cerebral artery of the opossum Didelphis albiventris was examined in 30 brains with the cervical segment of the spinal cord attached. For examination, the arterial system of the brains was perfused with colored latex and fixed in 20 per cent formalin. The caudal cerebral artery originated from the caudal communicating artery at the level of the cerebral peduncles, then went to the transversal fissure from where it sent three main branches to the mesencephalic tectum on the dorsal surface of the thalamus, the stria medullaris, the pineal body and the tentorial and medial surfaces of the cerebral hemisphere. The caudal cerebral artery was present in all specimens and gave rise to two main collateral branches - the tentorial hemispheric branch and the rostral tectal artery. The tentorial hemispheric branch originated from the caudal communicating artery on the right and left sides in 83.3 per cent and 80 per cent of the cases respectively, from the caudal communicating artery on both sides in 10 per cent of the samples and from the middle-rostral cerebral trunk in 6.7 per cent of the preparations ont the right side and in 10 per cent on the left side. The rostral tectal artery on the right was single in 96.7 per cent of the cases and double in 3.3 per cent; on the left side, the artery was single in all specimens. After giving rise to two collateral rami, the caudal cerebral artery crossed the dorsal surface of the thalamus, giving off small branches to the pineal gland and the stria medullaris. At the level of the rostral tubercle of the thalamus, the artery ran towards the medial surface of the cerebral hemisphere. The terminal branch anastomosed with the tentorial hemispheric ramus to form the caudal inter-hemispheric artery in 93.3 per cent and 86.7 per cent of the cases on the right and left sides, respectively.

Medida da velocidade de fluxo nas artérias cerebrais utilizando ultra-som Doppler transfontanela antes e após o tratamento cirúrgico da hidrocefalia / Transfontanellar Doppler ultrasound measurement of cerebral blood velocity before and after surgical treatment of hydrocephalus

Vinte e sete crianças portadoras de hidrocefalia de diversas etiologias, diagnosticadas pelo exame clínico, neurosonografia e tomografia cerebral computadorizada, foram submetidas a avaliação por ultra-som Doppler (US-Doppler) transfontanela para medida da velocidade de fluxo sanguíneo e cálculo do índice de resistência (IR) nas artérias cerebrais anteriores, médias e carótidas internas. Todas as crianças foram submetidas a avaliações no pré-operatório e no 1º, 7º, 30º e 60º dias do pós-operatório. Concluímos ser a técnica de neurosonografia e US-Doppler útil no diagnóstico da hidrocefalia, na indicação e controle das derivações liquóricas e no acompanhamento das modificações dos valores do IR comparando-os no pré e pós-operatório imediato e tardio do tratamento cirúrgico da hidrocefalia. Os resultados obtidos permitiram-nos ainda, pela comparação dos valores do IR entre as diversas artérias avaliadas nos diferentes estágios do estudo, concluir serem as artérias cerebrais anteriores representativas das alterações máximas que ocorrem na resistência vascular cerebral em pacientes pediátricos portadores de hidrocefalia.

Energetic and spatial constraints of arterial networks

Aneurismas intracranianos e vasculopatia de hiperfusäo em pacientes com malformaçöes arteriovenosas cerebrais resultam do elevado stress hemodinâmicos na rede arterial cerebral. O estabelecimento de uma norma para a geometria arterial cerebral deve resultar em melhores critérios preventivos e de planejamento terapêutico para essas patologias. Uma rede arterial deve distribuir-se no espaço para todo o órgäo perfundido, e ao mesmo tempo possibilitar a perfusäo tecidual com adequado custo energético e mínimo stress hemodinâmico. O custo total do fluxo sangüíneo é a soma do custo Pf para propulsäo do sangue através dos vasos (que aumenta com a reduçäo do calibre das artérias) e do custo metabólico Pm do tecido sangüíneo e dos vasos que diminui com a reduçäo do calibre das artérias). O equilíbrio entre Pf e Pm resulta no mínimo custo total quando artérias de grande e pequeno calibre organizam-se em uma hierarquia de ramificaçöes tal que o raio interno do vaso é proporcional ao cubo do fluxo sangüínio (princípio do trabalho mínimo), o que significa que em cada ramificaçäo arterial o raio do tronco (r0) e dos ramos (r1 e r2) estäo relacionados de acordo com a regra

Evaluación de los índices de flujos sanguíneos maternos y fetales en la colestasia intrahepática del embarazo / Evaluation of maternal and fetal blood flow indexes in pregnancy intrahepatic cholestasis

Nuestro objetivo fue observar si existen alteraciones de los índices de flujo sanguíneo en pacientes portadoras de una colestasia intrahepática del embarazo. Se estudiaron 51 pacientes gestantes de tercer trimestre, las que se dividieron en; grupo normal n=15, grupo con colestasia intrahepática del embarazo n=36; 21 pacientes anictéricas y 15 pacientes ictéricas, con bilirrubinemia >1,2 mg por ciento En todas se determinaron los índices de flujo en las arterias uterina, umbilicales y cerebrales fetales. No existieron diferencias significativas en la paridad, edad materna, edad gestacional, peso de nacimiento, ni apgar de los recién nacidos. Tampoco se apreciaron diferencias significativas en ninguno de los índices de flujo en los territorios mencionados. Concluimos que las pacientes portadoras de una colestasia intrahepática no presentan alteraciones de los índices de flujo evidenciables por medio de la técnica del doppler