老年高血压患者降压治疗对脑血液循环影响初探

目的探索老年高血压患者长期降压治疗对脑血液循环的影响。方法采用颈部血管超声测定全脑血流量（CBF）技术,前瞻性随访142例老年高血压患者降压治疗前、治疗后1／2年及1年时血压与血流动力学参数。结果老年高血压患者降压治疗后CBF增高（治疗前616．41±107．96mL／min,疗程1／2年时629．73±103．63mL／min,疗程1年时635．69±106．31mL／min,P〈0．05）,SBP降幅大者治疗后CBF高（疗程1／2年时β0．147,95％,CI0．022～0．272,P=0．021,疗程1年时B0．161,95％CI0．018～0．313,P=0．037）,基础DBP高者治疗后CBF下降风险大（疗程1／2年时0R1．117,95％CI1．001～1．247,P=0．048,疗程1年时0R1．213,95％CI1．028～1．473,P=0．024）。结论老年高血压患者积极降压治疗安全且益丁脑血液循环,但对基础DBP高者需加强监测。     

计算机体层摄影术灌注成像研究超早期脑梗死患者脑血流动力学状态

目的通过观察超早期脑梗死区域计算机体层摄影术灌注成像变化,分析超早期脑梗死区域脑血流动力学状态及影响因素。方法选择17例突发偏瘫或失语、发病时间少于6 h、计算机体层摄影术常规扫描阴性的患者,立即行灌注成像检查。分析灌注成像相关数据,并且与20例正常人群进行比较。结果6 h内脑梗死患者患侧灰质及白质脑血流量、脑血流容积明显低于对侧,差异有显著性(均P<0.05);脑梗死组对侧与对照组比较,灰质区域的脑血流量下降、脑血流容积上升、达峰时间上升,白质区域的脑血流量上升、达峰时间上升,差异有显著性(P<0.05);发病年龄与病灶侧脑血流动力学状态呈显著性相关(脑血流量r=-0.707、脑血流容积r=-0.658)(P<0.05)。结论超早期脑梗死患者计算机体层摄影术灌注成像不仅有病灶侧大脑血流动力学改变,而且还有对侧大脑血流动力学改变;患者年龄也是影响病灶侧大脑血流动力学状态相关因素之一。     

REGIONAL CEREBRAL BLOOD FLOW MEASUREMENTS IN THE DIAGNOSIS OF DEMENTIA

The Xenon-133 regional cerebral blood flow technique (rCBF) was used to assess cortical perfusion in a group of 15 elderly patients (mean age = 79.1, SD = 8.7) with a probable diagnosis of Dementia of the Alzheimer type (DAT). Nine had mild DAT and six were in the moderate stages of DAT. These patients were compared with 15 age and sex matched normal elderly controls (mean age = 75.1, SD = 5.6). RCBF was measured in each patient and control at rest with eyes closed. The DAT patients had significantly lower mean global CBF than normal controls (t = -4.63, p< 0,0001). In addition, a further 15 normal elderly subjects aged 60 to 92 were assessed and combined with the original 15 to allow calculation of a normal range of rCBF for elderly individuals. Seventy-three per cent of the DAT patients fell below the lower limit of the normal range (39.3 - 59.3 ISI units). These results show the possible usefulness of rCBF as an aid in the diagnosis of early DAT.     

Cerebral atrophy precedes the change in cerebral blood flow in patients with ischemic cerebrovascular disease: a short-term follow-up study.

Cerebral atrophy and the decrease in cerebral blood flow (CBF) progress with advancing age. Which of them takes first place, the changes in CBF or cerebral atrophy? We investigated longitudinal changes in CBF and cerebral atrophy in 14 patients with ischemic cerebrovascular disease (CVD): 11 patients with supratentorial lacunar infarction and 3 with carotid transient ischemia attack who were neurologically stable during the 1-3 years of observation. Cerebral atrophy was estimated by the brain atrophy index (BAI): one of the CT area measurement methods, and CBF was measured using the 133Xe inhalation technique. While significant progression of cerebral atrophy was observed, there was no significant change in CBF. Cerebral atrophy precedes the change in CBF and CVD.     

Cerebral Blood Flow and Metabolic Rate in the Conscious, Freely Moving Rat: The Effects of Hypercapnia, and Acute Ethanol Administration

We propose a simple method that can be used to measure cerebral blood flow (CBF), cerebral oxygen consumption (CMRO2), and cerebral glucose consumption (CMRglu) in the conscious, freely moving rat. The method is based on the classical Kety-Schmidt approach, and uses a chronic cannula in the confluens sinuum. We tested the method by investigating the response of CBF, CMRO2, and CMRglu to hypercapnia and used the approach to investigate the effects of acute alcohol administration. Severe hypercapnia (PaCO2 approximately 80 mmHg) increased the CBF by a factor of 3.5, decreased the CMRO2 by 30%, and had no significant effect on the CMRglu. Under normocapnic conditions moderate blood alcohol levels (100-200 mg%) caused no significant effects on CBF, CMRO2, or CMRglu, but high blood alcohol levels (250-400 mg%) decreased all three parameters by approximately 25%. Under hypercapnic conditions high blood alcohol levels had no effect on CBF, CMRO2, and CMRglu.     

Reduced cerebral perfusion in elderly men with silent myocardial ischaemia and nocturnal blood pressure dipping

ObjectiveKnowledge about the impact of cardiovascular disease on cerebral autoregulation and cognition in aging is sparse. The aim of our study is to examine the association between cerebral blood flow (CBF), silent ST segment depression (STDE) on ambulatory ECG (LTER) and nocturnal blood pressure variations in elderly men.MethodsIn a cross-sectional cohort study “Men born in 1914”, eighty 83-year-old men were examined by CBF, LTER and ambulatory blood pressure monitoring (ABPM). The presence and the degree of STDE were analyzed in relation to regional CBF in nocturnal blood pressure dippers/non-dippers.ResultsFourty-five (56%) study subjects had STDE, 25 at both day and night and 20 only daytime. Subjects with STDE expressed lower CBF in left frontal, temporal, inferior parietal regions and bilateral superior parietal regions compared to men without STDE. Low regional CBF was most frequent in subjects with daytime STDE. Subjects with nocturnal diastolic blood pressure dip and STDE (22 subjects; 35%) had lower mean CBF in the parietal lobe and also correlation between STDE and CBF (r = 0.31–0.44, p = 0.056–0.006) compared to non-dippers with STDE. The lowest CBF in nocturnal dippers was observed in subjects with maximal STDE daytime.ConclusionSilent myocardial ischemia may contribute to cerebrovascular disease in non-demented elderly men. Cerebral perfusion seems to be most vulnerable to myocardial ischemia in elderly with nocturnal blood pressure dipping.     

Orthostatic hypotension in Alzheimer's disease: result or cause of brain dysfunction?

In Alzheimer's disease (AD), an association was found between autonomic dysfunction and frontal hypoperfusion in brain during orthostatic testing. To ascertain whether frontal hypoperfusion is dependent on longitudinal effects of hemodynamic disturbances, or contributes to them, we studied the relationship between the presence of orthostatic hypotension (OH) and resting cerebral blood flow (CBF) in late stages of AD. Twelve women with senile dementia of Alzheimer type (SDAT), and 15 non-demented women (mean age 82.6 years, SD 3.8 vs 81.8 years, SD 3.5) were examined with the orthostatic test. Four of 12 patients with SDAT, and 9 controls had OH (defined as systolic blood pressure fall > or = 20 mmHg). CBF was determined under resting conditions using 600 Mbq 99mTc HMPAO single photon emission computerized tomography (SPECT), and quantified in cortical areas in relation to cerebellum. In patients with SDAT and OH, CBF was lower in frontal and parieto-frontal cortical areas than in SDAT patients without OH. The former group was younger and had a shorter dementia duration. No significant differences in CBF were observed between controls with vs without OH. No differences in SDAT patients with or without OH were observed in the Berger dementia scale or Katz' ADL index. No difference in incidence of symptoms related to autonomic disturbances (diarrhea, obstipation, dysphagia, vertigo) was observed in either the SDAT or control group with regard to OH presence. We conclude that during the course of AD, OH can contribute to frontal brain changes and may exacerbate the disease. The further involvement of frontal dysfunction in aggravating blood pressure dysregulation in the elderly is discussed.     

The severity of anaemia depletes cerebrovascular dilatory reserve in children with sickle cell disease: a quantitative magnetic resonance imaging study

Overt ischaemic stroke is one of the most devastating complications in children with sickle cell disease (SCD ). The compensatory response to anaemia in SCD includes an increase in cerebral blood flow (CBF ) by accessing cerebrovascular dilatory reserve. Exhaustion of dilatory reserve secondary to anaemic stress may lead to cerebral ischaemia. The purpose of this study was to investigate CBF and cerebrovascular reactivity (CVR ) using magnetic resonance imaging (MRI ) in children with SCD and to correlate these with haematological markers of anaemia. Baseline CBF was measured using arterial spin labelling. Blood‐oxygen level‐dependent MRI in response to a CO ₂ stimulus was used to acquire CVR . In total, 28 children with SCD (23 not on any disease‐modifying treatment, 5 on chronic transfusion) and 22 healthy controls were imaged using MRI . Transfusion patients were imaged at two time points to assess the effect of changes in haematocrit after a transfusion cycle. In children with SCD , CBF was significantly elevated compared to healthy controls, while CVR was significantly reduced. Both measures were significantly correlated with haematocrit. For transfusion patients, CBF decreased and CVR increased following a transfusion cycle. Lastly, a significant correlation was observed between CBF and CVR in both children with SCD and healthy controls.     

The effect of losartan on global and focal cerebral perfusion and on renal function in hypertensives in mild early ischaemic stroke

BACKGROUND: Secondary prevention of stroke with antihypertensive drugs is now standard practice, but it is unclear how soon after a cerebrovascular event antihypertensive therapy should be initiated or re-started. Due to impaired cerebral autoregulation, changes in systemic blood pressure may be reflected in cerebral perfusion, especially in hypertensive patients immediately post-stroke. Conversely, early initiation in hospital may better assure continued long-term treatment. We have investigated the effect of the angiotensin II receptor antagonist (ARA) losartan on mean arterial blood pressure (MABP), global and focal cerebral blood flow (CBF), and glomerular filtration rate (GFR) in hypertensive patients 2-7 days after stroke. METHODS: Twenty-four patients without occlusive carotid disease but with MABP between 110 and 145 mmHg were studied within 2-7 days of ischaemic stroke/transient ischaemic attack (TIA). They were randomized to receive either placebo or losartan (25 or 50 mg daily). MABP and internal carotid artery (ICA) flow were measured at baseline, over the following 24 h and at 2 weeks. Brain hexamethylpropyleneamine oxime single photon emission computed tomography (HMPAO SPECT) was performed before dosing and at the estimated time of peak drug effect (6-8 h after the first dose). GFR was measured at baseline and at 2 weeks. RESULTS: The mean National Institutes of Health (NIH) score of randomized patients was 2.6; losartan was generally well tolerated and no patient suffered a deterioration in neurological function. A mean placebo-corrected intra-subject reduction in MABP of 9.5 mmHg was observed in treated patients from 1-12 h (P = 0.0001), with a maximal fall of 18.1 mmHg at 9 h post-dose (P = 0.002). No change occurred in ICA flow, or cortical or hemispheric CBF measured by HMPAO SPECT. No significant change in GFR was seen within or between groups. DISCUSSION: Losartan may be introduced within 2-7 days of mild stroke in hypertensive patients in whom significant carotid occlusive disease has been excluded without affecting global or regional CBF, or affecting GFR.     

双排螺旋CT脑灌注成像在超早期脑梗死诊断中的价值

目的　探讨双排螺旋CT脑灌注成像技术在超早期脑梗死诊断中的意义。　方法　 对18例短暂性脑缺血发作患者行头部CT平扫,选择基底核区或感兴趣区行CT脑灌注成像,获 取脑血流量(CBF)、脑血容量(CBV)和对比剂平均通过时间(MTT)图;出院时复查CT,与 入院时CT片比较。对同一例患者脑灌注后资料作统计学分析。　结果　患者发病90min后,CT 脑灌注即可显示出病灶区域血流灌注异常,与对侧相比CBF、CBV下降,MTT延长。对于CT平 扫未见病灶的患者,可预示有无梗死灶的存在、位置及范围;对于已有梗死灶的患者可预示病灶 的发展趋势。12例CT脑灌注异常的同一例患者,左、右两侧半球脑实质内CBF、CBV及MTT差 异均具有显著意义(P<0.05～0.01),6例无CT脑灌注异常者,差异无显著意义(P>0.05～ 0.01)。　结论　CT脑灌注成像技术可超早期预示脑梗死病灶及其发展趋势,有重要的临床应用 价值。统计学分析可作为诊断脑血流灌注异常的一种补充。     

脑梗死患者脑血流动力学的多层螺旋CT灌注成像研究

目的 探讨CT灌注成像(CTPI)在老年性脑梗死脑血流动力学研究中的价值.方法 48例临床拟诊脑梗死的患者,发病24 h内行CT 16层平扫及CTPI检查,测定兴趣区的脑血流量(CBF)、对比剂平均通过时间(MTT)和对比剂峰值时间(TTP),并与对侧相应脑组织灌注参数比较;所有病例3～10 d后行MRI随访.结果 本组中40.9%的患者CT平扫显示缺血灶,93.2%的患者CTPI显示异常灌注.CTPI发现异常灌注的敏感性为93.2%,特异性为100%;缺血区CBF减低,MTT、TTP延长,与对照区域比较差异有统计学意义(P＜0.01).结论 CTPI能够敏感地反映缺血脑组织的血流动力学状态,为老年性脑梗死的早期诊断、早期治疗提供重要信息.

Abstract：

Objective To study the value of CT perfusion imaging(CTPI)on brain hemodynamic of the aged with cerebral infarction. Methods The 48 patients who were doubted with cerebral infarction underwent 16-slice CT plain scanning and CTPI within 24 hours of onset. The cerebral blood flow(CBF), mean transit time(MTT)and time to peak(TTP)of contrast-medium in region of interest(FOV)were used as brain hemodynamic parameters in comparation with contralateral regions. All cases were followed up with MRI after 3-10 days. Results Ischemia lesion was found on CT plain scanning in 40.9% of patients, while 93.2% of patients showed abnormal perfusion on CTPI. The sensibility of CTPI in identifying ischemia area was 93.2%, and the specificity was 100%. CBF in research area was significantly reduced, MTT and TTP were remarkably increased in contrast to counterparts(P＜0.01). Conclusions CT perfusion imaging can sensitively reveal the hemodynamic condition of cerebral ischemia, which could provide the important information for early diagnosis and treatment of the elderly with brain infarction.     

First-dose effects of enalapril and atenolol upon blood pressure and cerebral blood flow in patients with mild hypertension on diuretic therapy

The present single-blind, randomised, cross-over, placebo-controlled study was set up to compare the first-dose effects upon blood pressure (BP) and cerebral blood flow (CBF, measured by Xenon inhalation) of a single oral dose of atenolol 50 mg and enalapril 5 mg in ten hypertensive patients receiving a thiazide diuretic. It was found that a) the timing and degree of fall in BP after the first dose of atenolol and enalapril on a diuretic background were similar and generally not associated with symptoms or a fall in CBF, and b) dizziness, which is sometimes associated with the first-dose effect of ACE inhibitors in hypertensives on diuretics, can occasionally occur accompanied by a substantial fall (43%) in CBF in the absence of marked falls in systolic blood pressure. It is suggested that the latter event may be linked to a disturbance of cerebral autoregulation in part dependent on localised renin-angiotensin systems.     

The short-term effects of reducing elevated blood pressure in elderly patients with propranolol and dyazide

Propranolol and Dyazide (25 mg hydrochlorothiazide and 50 mg triamterene) were used singly to reduce the elevated blood pressure (systolic ranging from 170 to 271 mmHg and diastolic ranging from 100 to 141 mmHg) of 38 elderly hypertensive patients whose ages ranged from 69 to 91 years. Each compound was administered for a period of four weeks with a wash-out period of four weeks in between. The following parameters were assessed before and after each treatment period: cerebral blood flow (CBF), mental functions, cardiac output (CO), electrocardiogram, glomerular filtration rate (GFR) and serum biochemistry. Both systolic and diastolic blood pressure were significantly reduced following the administration of either compound. No significant change in CBF and CO could be observed after reducing the blood pressure whether Propranolol or Dyazide was used. The GFR was, however, significantly reduced and the plasma creatinine significantly increased following Dyazide but not Propranolol administration. As expected the administration of the latter compound was associated with a significant bradycardia. No significant change could be observed in the other parameters studied.     

Transdermal glyceryl trinitrate lowers blood pressure and maintains cerebral blood flow in recent stroke

High blood pressure (BP) is common in acute stroke and is independently associated with a poor outcome. Lowering BP might improve outcome if it did not adversely affect cerebral blood flow (CBF) or cerebral perfusion pressure. We investigated the effect of glyceryl trinitrate ([GTN] an NO donor) on quantitative CBF, BP, and cerebral perfusion pressure in patients with recent stroke. Eighteen patients with recent (<5 days) ischemic (n=16) or hemorrhagic (n=2) stroke were randomly assigned (2:1) to transdermal GTN (5 mg) or control. CBF (global, hemispheric, arterial territory, and lesion, using xenon computed tomography) and BP (peripheral and central) were measured before and 1 hour after treatment with GTN. The effects of GTN on CBF and BP were adjusted for baseline measurements (ANCOVA). GTN lowered peripheral systolic BP by (mean) 23 mm Hg (95% CI, 2 to 45; P=0.03) and central systolic BP by 22 mm Hg (95% CI, 0 to 44; P=0.048). In contrast, GTN did not alter CBF (mL/min per 100 g): global -1.2 (95% CI, -6.5 to 4.2; P=0.66) and ipsilateral hemisphere -1.4 (95% CI, -7.6 to 4.9; P=0.65) or area of stroke oligemia, penumbra, or core (as defined by critical CBF limits). Contralateral CBF did not change: hemisphere 0 (95% CI, -7 to 6; P=0.96). GTN did not alter cerebral perfusion pressure or zero-filling pressure. Significant reductions in BP after transdermal GTN are not associated with changes in CBF or cerebral perfusion pressure or cerebral steal in patients with recent stroke. Trials need to assess the effect of lowering BP on functional outcome.     

Theophylline effect on the cerebral blood flow response to hypoxemia

Cerebral oxygen delivery (CO2D) remains nearly constant over a wide range of cerebral perfusion pressure and arterial oxygen content. In response to a decrease in arterial oxygen content secondary to hypoxemia, cerebral blood flow (CBF) increases, a response likely mediated by the release of adenosine. We studied the effect of theophylline, a potent adenosine antagonist, on CBF and cerebral oxygen delivery (CO2D) during hypoxemia in five healthy adult male volunteers. The CBF was measured using 133Xe clearance under conditions of (1) normoxemia (O2 saturation greater than 95 percent); (2) hypoxemia (O2 saturation = 80 percent); (3) normoxemia following aminophylline (the ethylene diamine salt of theophylline) 6 mg/kg intravenously; and (4) hypoxemia following aminophylline. Aminophylline decreased CBF and CO2D during both normoxemia and hypoxemia, but did not prevent the increase in CBF accompanying hypoxemia, suggesting that the increase in CBF in response to hypoxemia may not be mediated by adenosine or that customary doses of aminophylline are insufficient to inhibit adenosine-mediated cerebral vasodilation in response to hypoxemia. The significant decrease in CBF and CO2D observed following aminophylline is potentially clinically important and should be considered in the selection of bronchodilator therapy.     

The effect of continuous positive airway pressure on total cerebral blood flow in healthy awake volunteers

Purpose

Continuous positive airway pressure (CPAP) is the gold standard treatment for obstructive sleep apnea. However, the physiologic impact of CPAP on cerebral blood flow (CBF) is not well established. Ultrasound can be used to estimate CBF, but there is no widespread accepted protocol. We studied the physiologic influence of CPAP on CBF using a method integrating arterial diameter and flow velocity (FV) measurements obtained for each vessel supplying blood to the brain.

Methods

FV and lumen diameter of the left and right internal carotid, vertebral, and middle cerebral arteries were measured using duplex Doppler ultrasound with and without CPAP at 15 cm H₂O, applied in a random order. Transcutaneous carbon dioxide (PtcCO₂), heart rate (HR), blood pressure (BP), and oxygen saturation were monitored. Results were compared with a theoretical prediction of CBF change based on the effect of partial pressure of carbon dioxide on CBF.

Results

Data were obtained from 23 healthy volunteers (mean?±?SD; 12 male, age 25.1?±?2.6 years, body mass index 21.8?±?2.0 kg/m²). The mean experimental and theoretical CBF decrease under CPAP was 12.5 % (p?<?0.001) and 11.9 % (p?<?0.001), respectively. The difference between experimental and theoretical CBF reduction was not statistically significant (3.84?±?79 ml/min, p?=?0.40). There was a significant reduction in PtcCO₂ with CPAP (p?=?<0.001) and a significant increase in mean BP (p?=?0.0017). No significant change was observed in SaO₂ (p?=?0.21) and HR (p?=?0.62).

Conclusion

Duplex Doppler ultrasound measurements of arterial diameter and FV allow for a noninvasive bedside estimation of CBF. CPAP at 15 cm H₂O significantly decreased CBF in healthy awake volunteers. This effect appeared to be mediated predominately through the hypocapnic vasoconstriction coinciding with PCO₂ level reduction. The results suggest that CPAP should be used cautiously in patients with unstable cerebral hemodynamics.     

The effect of high-dose phenylephrine versus epinephrine on regional cerebral blood flow during CPR

Prior studies have not found the alpha agonist phenylephrine, in a dose of 0.1 mg/kg, to be as effective as 0.20 mg/kg of epinephrine in improving regional cerebral blood flow (CBF) during CPR in swine. We undertook this study to assess whether higher doses of phenylephrine might improve regional CBF. Fifteen swine were allocated to receive either epinephrine 0.2 mg/kg, phenylephrine 1.0 mg/kg, or phenylephrine 10 mg/kg. Regional CBF measurements were made during normal sinus rhythm, during CPR, and during CPR following drug administration. Epinephrine 0.2 mg/kg was significantly better in improving regional CBF to the left and right cerebral cortices, cerebellum, midbrain, and cervical cord than was phenylephrine 1.0 mg/kg. There was no significant difference in regional CBF between the animals receiving epinephrine 0.2 mg/kg and phenylephrine 10 mg/kg. The study shows that large doses of epinephrine and phenylephrine may be required during CPR to improve regional cerebral blood flow following a prolonged arrest.     

Cerebral Blood Flow in Hyperammonemia: Heterogeneity and Starling Forces in Capillaries

In the brain hyperammonemia interferes with ion homeostasis, membrane potentials, neurotransmission, and neurotransmitter recycling and reduces metabolic rates for oxygen and glucose. Because, cerebral blood flow (CBF) is closely coupled to metabolism, CBF is most often reduced in diseases associated with hyperammonemia. However, in severe cases of hyperammonemia, as in patients with acute liver failure, Reye's syndrome, and inherited metabolic disorders of the urea cycle, the normal regulation of CBF is also impaired. One of the most prominent findings is a failure of CBF autoregulation that uncouples metabolism from CBF. Clinically failure of autoregulation may imply that both cerebral hypoxia and hyperaemia may develop in the patient depending on the driving pressure of the brain, i.e., cerebral perfusion pressure. In addition a gradual nonreactive dilatation of the cerebral arterioles often aggravates the mismatch between nutritive demands and delivery in the brain. The reason for arteriolar dilation and homogeneous capillary blood flow is not settled but seems not to be mediated by excessive release of nitro oxide. More likely the arachidonic acid cascade with increased synthesis of prostaglandins, cytochrome P450 metabolites, and potassium channel activation are implicated in this vasodilatation. The combination of cerebral hyperaemia, increased hydrostatic capillary blood pressure, and accumulation of organic and nonorganic osmolytes within the brain during hyperammonemia clearly will favor cerebral capillary water influx. This imbalance between colloid osmotic and hydrostatic pressures in patients with severe hyperammonemia means that simple interventions based on physiological principles may help ameliorate cerebral hyperaemia and water influx. Thus, it is suggested that not only monitoring of intracranial pressure (ICP) and cerebral perfusion are pivotal to help prevent high ICP but also basic clinical information, such as Tp, PaCO₂, and plasma sodium/glucose concentrations, should be closely followed and corrected.     

Cerebral hemodynamics in multiple cerebral infarction with or without dementia

Cerebral blood flow and metabolism in 25 patients with multiple cerebral infarcts (14 with dementia) and 5 healthy age-matched controls were measured to investigate the difference in cerebral blood low (CBF) and cerebral oxygen consumption (CMRO2) between patients with dementia and patients without dementia. None of the patients had any lesions in the cortex, but all had multiple lesions in the basal ganglionic region, and in the white matter, according to CT images. CBF, CMRO2 and oxygen extraction fraction were measured by positron emission tomography (PET) using the 15O2, C15O2 steady state inhalational technique. In patients with multiple cerebral infarcts the absolute values of CBF and CMRO2 were decreased significantly from normal control values, and there was no significant difference in the absolute values of CBF and CMRO2 between patients with dementia and patients without dementia. In most patients with dementia, relative values (regional value/mean cortical value) of CBF and CMRO2 decreased in the frontal and the parietal cortex. Four patients had repeated PET studies. In two of them, decrease in CMRO2 was preceded by decrease in CBF. These results suggest that dysfunction of frontal cortex and parietal cortex, and chronic ischemia might be related to the occurrence of dementia in patients with multiple cerebral infarcts, which were in the basal ganglia and the white matter.     

Blood Pressure is Associated With Cerebral Blood Flow Alterations in Patients With T2DM as Revealed by Perfusion Functional MRI

Type 2 diabetes mellitus (T2DM) and hypertension are both associated with cognitive impairment and brain function abnormalities. We investigated whether abnormal cerebral blood flow (CBF) patterns exists in T2DM patients and possible relationships between aberrant CBF and cognitive performance. Furthermore, we examined the influence of hypertension on CBF alterations in T2DM patients.T2DM patients (n = 38) and non-T2DM subjects (n = 40) were recruited from clinics, hospitals, and normal community health screenings. Cerebral blood flow images were collected and analyzed using arterial spin labeling perfusion functional magnetic resonance imaging (fMRI). Regions with major CBF differences between T2DM patients and non-T2DM controls were detected via 1-way ANOVA. The interaction effects between hypertension and T2DM for CBF alterations were also examined. Correlation analyses illustrated the association between CBF values and cognitive performance and between CBF and blood pressure.Compared with non-T2DM controls, T2DM patients exhibited decreased CBF, primarily in the visual area and the default mode network (DMN); decreased CBF in these regions was correlated with cognitive performance. There was a significant interaction effect between hypertension and diabetes for CBF in the precuneus and the middle occipital gyrus. Additionally, blood pressure correlated negatively with CBF in T2DM patients.T2DM patients exhibited reduced CBF in the visual area and DMN. Hypertension may facilitate a CBF decrease in the setting of diabetes. T2DM patients may benefit from blood pressure control to maintain their brain perfusion through CBF preservation.