Orthostasis as a test for cerebral autoregulation in normal persons and patients with carotid artery disease.

Orthostasis reduces mean flow velocity (FVmean) in cerebral arteries. This might be used as an alternative provocation test for cerebral hemodynamics in patients with carotid artery disease (CAD). In 21 unilateral CAD patients and 21 controls, FVmean in both middle cerebral arteries (MCA) was measured by transcranial Doppler, together with blood pressure (BP) and heart rate (HR) during a tilt table test. Cerebrovascular reserve (CVR) was measured by an acetazolamide test. In all cases, FVmean dropped to a lower level (controls: 81.9 +/- 9.4% of baseline; patients: 84.3 +/- 7.9% symptomatic side, 85.6 +/- 9.0% contralateral). Impaired CVR patients showed a smaller (p < 0.01) decrease (90.6 +/- 3.3%) compared to contralateral (84.9 +/- 6.0%), to normal CVR patients (81.1 +/- 7.8%) and to controls. Heart rate increased in both groups (controls: +16.6 +/- 9.9%, patients +10.3 +/- 9.9%; p < 0.01); BP showed no change. Orthostasis induces a decrease of MCA FVmean as already previously described. This decrease is significantly smaller in patients with impaired CVR. Since BP does not change, some authors explain the lower MCA Fvmean during orthostasis as caused by sympathetic induced vasoconstriction of cerebral resistance vessels. The authors speculate that in impaired CVR-patients autoregulative protection against ischemia might limit vasoconstriction. In combination with standard tests for measurement of CVR, this test might be useful for evaluation of cerebral autoregulation.     

Phase-Contrast Magnetic Resonance Angiography for the Determination of Cerebrovascular Reserve

Cerebrovascular reserve (CVR) is the potential for cerebral arteriolar dilatation to occur, in response to decreased cerebral perfusion pressure, in order to maintain constant cerebral blood flow. Diminution or absence of CVR is considered a risk factor for stroke. Current methods for determining CVR include singlephoton emission computed tomography, positron emission tomography and transcranial Doppler (TCD) ultrasonography. However, significant advantages could derive from the utilization of magnetic resonance angiography (MRA) based on the concurrent acquisition of hemodynamic information (CVR and collateral flow) with phase?contrast (PC) techniques and vascular morphology with three?dimensional, time?of?flight methods. With a 1.5?T scanner and acetazolamide (AZM), an arteriolar dilator, CVR was determined in 7 normal subjects. Mean flow velocity in the middle cerebral arteries was determined by PC MRA before and after AZM administration. For comparative purposes, mean flow velocities in the same middle cerebral arteries were determined by TCD before and after AZM administration. The mean flow velocities were as follows (mean ± standard deviation, n = 7): 40 ± 8 (PC MRA) versus 61 ±10 cm/sec (TCD) before AZM treatment and 58 ±11 (PC MRA) versus 85 ±15 cm/sec (TCD) after AZM administration. The increase in mean flow velocity (before vs after AZM), that is, the CVR, was 45 ±11 % as shown by PC MRA and 39 ± 14% as shown by TCD. Although significant differences were present between the mean flow velocities measured before and those after AZM administration, as determined by PC MRA and TCD, the CVR was not significantly different (45 vs 39%, respectively). These preliminary results suggest that PC MRA may be a method for determining CVR.     

Investigation of cerebrovascular reactivity using transcranial Doppler sonography. Evaluation and comparison of different methods

Cerebrovascular reactivity was investigated in 20 patients and 20 healthy subjects by Transcranial Doppler (TCD) sonography with four methods. Flow velocity at the middle cerebral artery (MCA) was recorded in the following conditions: a) rest; b) 60" hyperventilation; c) maximum voluntary apnea; d) air re-breathing in a closed circuit; e) 30' following the intravenous injection of 10 mg/kg acetazolamide. Circulatory and respiratory diseases influencing MCA velocity were exclusion factors. Flow velocity variations observed in the four experimental conditions (b-e) were transformed into % values of basal velocity; in the c) and d) tests the Reactivity Indices were computed, i.e. the ratios between velocity changes and PaCO2 increases. Each method proved effective in modifying MCA flow velocity, and produced typical patterns. Apnea, CO2 inhalation during air re-breathing and acetazolamide injection revealed impaired cerebrovascular reactivity in patients with multifocal ischemic lesions. A good correlation was observed comparing the apnea method to both CO2 inhalation and acetazolamide injection.     

Multimodal tests of cerebrovascular reactivity in migraine: a transcranial Doppler study

Summary Altered cerebral vasoreactivity (CVR) has been implicated in migraine. To test this hypothesis, we studied CVR as measured by transcranial Doppler ultrasound (TCD) in 11 migraineurs and 12 healthy controls of similar age. Mean flow velocities (MFV) in the middle cerebral artery (MCA) were recorded during a cognitive and two motor tasks. MFV in the posterior cerebral artery (PCA) were measured during photic stimulation and observation of complex images. The increase of MFV in the MCA during the cognitive task was greater in migraineurs than in controls (9.1% vs 5.0% ;P = 0.06). The increase of MFV in both tests for PCA reactivity was significantly greater in migraineurs than in controls: 17.4% vs 9.9% for photic stimulation (P < 0.05) and 20.3% vs 10.2% for observation of complex images (P<0.05). Owing to overlap of individual results, the discriminative value of both tests was unsatisfactory. The variability of flow velocities as measured by standard deviations of MFV was significantly greater in migraineurs than in controls during all tests of PCA vasoreactivity. Differences in CVR between migraineurs and normal controls may be detected by TCD testing, in particular in the PCA territory. For individual diagnostic purposes, CVR tests proved to be insufficient.     

CBF and transcranial Doppler sonography during vasodilatory stress tests in patients with common carotid artery occlusion.

Cerebral blood flow (CBF) and the cerebral vasoreactivity was measured in patients with cerebrovascular disease and longstanding occlusion of the common carotid artery (CCA). In addition, regional CBF was correlated with transcranial doppler (TCD) measurements at baseline and during 6% CO2 inhalation and after intravenous administration of 1 g of acetazolamide. Twelve patients with a mean age of 62 years (range 45 to 71 years) were included, and the data compared to age-matched healthy controls. CBF was measured by intravenous injection of xenon-133 and SPECT (Tomomatic 564). TCD of the middle cerebral artery (MCA) was done by EME TC-64B. A very low global CBF value of 28 +/- 5 (SD) ml 100 g-1 min-1 was found at baseline as compared to 55 +/- 5 ml 100 g-1 min-1 in the normal controls. During 6% CO2-inhalation and after acetazolamide administration, CBF increased by 58 +/- 24% and 51 +/- 21%, respectively, indicating substantial collateral supply. Correlative analysis of CBF in the MCA territory and TCD in the MCA showed statistical significance only for the pooled data, i.e. compiling the data obtained during baseline and the two vasodilatory tests, and then only for the mean and peak TCD velocity (e.g. r = 0.59, p less than 0.002, n = 35, mean velocity, right side). We conclude that TCD measurements do not predict regional CBF in patients with CCA occlusion. The study emphasizes that these two methods yield supplementary information, with TCD measurements providing information of the circle of Willis and CBF studies of the flow distribution.     

Evaluation of cerebrovascular reserve using xenon-enhanced CT scanning in patients with symptomatic middle cerebral artery stenosis

Cerebrovascular reserve (CVR) is an important prognostic factor in patients with major cerebral arterial steno-occlusive disease. However, few studies have examined CVR in symptomatic intracranial stenosis without ipsilateral extracranial internal carotid artery stenosis. This study sought to evaluate CVR in patients with symptomatic middle cerebral artery (MCA) stenosis using xenon-enhanced computed tomography (Xe/CT) with acetazolamide (ACZ) challenge. Twelve patients with symptomatic MCA stenosis were recruited. All patients were examined by Xe/CT to quantitatively measure resting cerebral blood flow (CBF) and received ACZ challenge to evaluate CVR. For resting CBF, no significant differences were found between the sides in four regions of interest. After the ACZ challenge test, the CVR was significantly different between hemispheres (ipsilateral versus contralateral CVR: 12.9 ± 24.3% versus 28.0 ± 16.8%, respectively; p = 0.005) and in the MCA territory (ipsilateral versus contralateral CVR: 8.7 ± 24.7% versus 29.3 ± 24%, respectively; p = 0.003). However, no significant differences in CVR were detected between cortical comparisons and white matter comparisons from the two sides. Thus, ACZ-challenge Xe/CT is useful for the measurement of CBF and CVR in these patients. Impaired CVR is an important characteristic of patients with symptomatic MCA stenosis.     

Detection of impaired cerebrovascular reactivity in patients with chronic cerebral ischemia using whole-brain 7T MRA

BackgroundCerebrovascular reactivity (CVR) to acetazolamide (ACZ) on single-photon emission computed tomography (SPECT) can be used to assess the severity of chronic cerebral ischemia; however, this is an invasive method. We examined whether whole-brain magnetic resonance angiography (MRA) at 7T could non-invasively detect impaired CVR in patients with chronic cerebral ischemia by demonstrating the leptomeningeal collaterals (LMCs).MethodsFifty-seven patients with symptomatic unilateral cervical stenosis underwent whole-brain time-of-flight MRA at 7T and cerebral perfusion SPECT before/after the ACZ challenge. MRA images were visually assessed based on 6-point grading systems to evaluate the development of LMCs toward the middle cerebral artery (MCA) and antegrade flow of MCA. CVR of the affected side was calculated from the SPECT data. Subsequently, we compared the LMC grades on MRA with CVR on SPECT.ResultsCVR was significantly lower in grades ≥ 2 of LMCs than in grades 0–1 (P < 0.05) when applying LMCs from the anterior cerebral artery (ACA) and/or posterior cerebral artery (PCA). These differences were more evident than those in the grading of the antegrade MCA flow. The LMC grades from ACA/PCA readily detected reduced CVR (< 18.4%) with a sensitivity/specificity of 0.79/0.82.ConclusionThe development of LMCs on whole-brain MRA at 7T can non-invasively detect reduced CVR with a high sensitivity/specificity in patients with unilateral cervical stenosis.     

Relationship between the flow pattern and vasomotor reactivity in the ophthalmic artery,siphon and vessels within the circle of Willis in the unilateral internal carotid artery occlusion

Abstract

The aim was to study a relationship between the flow pattern in the ophthalmic artery (OA), the siphon and vessels within the circle of Willis. 27 patients, 22 males and 5 females; mean age 63 ± 15 years (SD) with unilateral occlusion of the internal carotid artery (ICA) were examined by 3-dimensional Transcranial Doppler scanner Flow signals from the OA, the siphon and intracranial vessels were registered before and after i.v. injection of 1 g acetazolamide. Pathological flow pattern was found in 18 patients in the OA on the occluded side consisting of 12 retrograde and 6 isoelectric flow directions. After acetazolamide injection retrograde systolic velocities (SV) increased significantly (p < 0.01), but anterograde velocities remained unchanged as did 3 isoelectric flow patterns, 2 turned to retrograde and one to anterograde flow direction. In the siphon lower resting anterograde mean velocities (MV) were found on both sides (p < 0.05) compared to normal subjects. Six patients had the same retrograde flow as in the OA. After acetazolamide MV in the siphon increased (p <0.01) only on the nonoccluded side. Baseline retrograde ophthalmic SVand MV in the siphon correlated (p < 0.01 and p < 0.05 respectively) with MV in the middle cerebral artery (MCA) according to linear regression analysis (x - 0.78 and 0.59 respectively). All patients, having impaired vasomotor reactivity (VMR) <11% in the anterior cerebral artery (ACA) on the occluded side, had pathological flow pattern in the OA. Patients with greatest difference (A) between MV in the ACA on the nonoccluded and occluded side had a tendency to anterograde flow (r = 0.56, p < 0.05). Pulsative index (PI) in the ACA on the occluded side was lowest in the category with retrograde flow in the OA (0.67± 0.14) and differed (p < 0.05) from normals and from the category with isoelectric and anterograde flow. Correlation of retrograde flow direction in the OA and baseline MV in the MCA and low PI in the ACA on the occluded side indicates a supplying ophthalmic collateral to the anterior brain circulation. Impaired VMR in the ACA on the occluded side in connection with pathological flow pattern in the OA may reflect an exhaustion of the ACA as a supplying vessel. [Neurol Res 1996; 18: 521-527]     

Cerebrovascular reactivity in young and old patients with obstructive sleep apnea

ObjectiveImpaired cerebrovascular reactivity (CVR) in patients with obstructive sleep apnea syndrome (OSAS) increases the risk of ischemic stroke. CVR also decreases with age in normal individuals. However, it is unclear whether OSAS affects CVR differently in young and old patients. The aim of this study was to compare CVR in old and young patients with OSAS via transcranial Doppler (TCD) measurements of changes in cerebral blood flow velocity in the middle cerebral artery (MCAmv) during breath holding and hyperventilation.MethodsA total of 20 old patients (≥65 y) and 40 young patients (<65 y) with similar distributions of sex and OSAS severity were recruited for this study. The breath-holding index (BHI) and the hyperventilation index (HVI) were calculated to measure CVR.ResultsNo differences were found in MCAmv at baseline, apnea or hyperventilation between the two groups with different OSAS severities. However, reduced BHI (P < 0.01) and HVI (P < 0.01) were found in the young group with increasing severity of OSAS. Notably, the decline in BHI and HVI associated with OSAS severity was steeper in young patients than in old patients (P < 0.01).ConclusionsThese findings suggest that CVR in young patients is more impacted by OSAS severity than that in old patients, suggesting the existence of age-related cerebrovascular susceptibility to OSAS.     

Scientific Session IV: Impact of Neurosonology on Therapeutic Decisions

To assess the impact of brain activation and subarachnoid haemorrhage (SAH) on flow velocity changes after visual stimulation, we examined 27 healthy controls ( 13 subjects examined with closed and opened eyes), 12 patients with SAH while eyes were kept open, 9 patients under general anesthesia without brain disease and 5 patients with vegetative state after brain injury. All subjects were examined with bilateral TCD monitoring of one PCA and contralateral MCA during rest (30s) and stimulation with 10 Hz flashlight (30s). Ten cycles of stimulation were averaged for estimation of the specific flow response (SFR), which was computed as percent increase of PCNMCA ratio. In controls, SFR was significantly higher with opened eyes (mean, 15.8%) than closed eyes (mean, 11.8%, p < 0.01, Wilcoxon test). SFR was significantly decreased in early stage of SAH (mean, 4,83%, p < 0.01) and normalized during course of disease. Four of 5 patients with abolished SFR suffered delayed ischemia due to vasospasm. Of 7 patients with preserved SFR, 5 had vasospasm by ultrasonic or angiographic criteria, but none had delayed ischemia. No SFR was observed in general anesthesia and apallic state. We conclude that vasoneuronal coupling depends on stimulus directed attention. Furthermore, abolished SFR in SAH might indicate a high risk of delayed ischemia due to vasospasm.     

Vasoreactivity in patients with periventricular white matter lucency

OBJECTIVES: Cerebral hypoperfusion has been evidenced in patients with periventricular white matter lucency (PWML), however, our knowledge is limited regarding vasoreactivity (VR) changes in these patients. Therefore, we compared the cerebral blood flow velocity (CBFV) responses during different vasoregulatory challenges in healthy volunteers, to those in patients with PWML. MATERIAL AND METHODS: In 20 patients with PWML and in 20 healthy volunteers the VR of the middle cerebral artery (MCA) system was measured by analyzing the changes of CBFV during different stimulation paradigms (ventilation, tilting and acetazolamide tests). During transcranial Doppler (TCD) registration the systemic blood pressure, the expiratory partial CO(2) pressure (pCO(2)) and the electroencephalograph (EEG) were monitored. RESULTS: The relative velocity change was significantly smaller in the PWML group than in the normal control group during hypercapnia (16 +/- 12% vs 32 +/- 17%; P < 0.001) and this finding was confirmed by assessment of pCO(2)-corrected velocity change (4.7 +/- 3.7 cm/s/kPa vs 18.4 +/- 6.8 cm/s/KPa; P < 0.001). Although CBFV measurements during acetazolamide test tended to support these findings, the changes of other parameters measured did not reach the level of significance. One patient showed considerable orthostatic reaction (mean arterial blood pressure decrease by 70 mmHg) but it was not associated with significant changes in CBFV. CONCLUSION: Patients with PWML showed an impaired VR in the MCA flow territory supporting the concept of the microangiopathic origin of leukoaraiotic changes.     

Assessment of ophthalmic artery collateral pathway in the hemispheric cerebral hemodynamics in patients with severe unilateral carotid stenosis

The role of ophthalmic artery collateral pathway in hemispheric hemodynamics in patients with severe carotid stenosis is controversial. The aim of the present study was to address this question comparing the asymmetry of the velocity in middle and anterior cerebral arteries (MCAs and ACAs) and cerebrovascular reactivity (CVR) in MCA on stenotic side in the patients with unilateral severe stenosis of internal carotid artery (ICA) in patients with and without ophthalmic artery collateral pathway. The cohort of 118 patients with carotid stenosis was prospectively assembled. Fifty patients who had severe unilateral ICA stenosis (71%-99%) by Duplex Ultrasound (DUS) were observed by transcranial Doppler (TCD). Cerebral blood flow velocity in MCA and ACA in both sides, direction of blood flow in ophthalmic artery (OA) and CVR on the side of stenosis were determined. There were 14 patients with retrograde blood flow in OA (Group I). The remaining 36 patients with anterograde flow in OA composed Group II. The degree of interarterial asymmetry of peak and mean velocity (Vpeak and Vmean) in MCA and ACA and CVR in MCA were compared in both groups. The degree of ACA asymmetry by Vpeak was 44.0% +/- 6.9% in Group I and 38.3% +/- 3.9% in Group II (p = 0.49), by Vmean 40.3% +/- 6.7% and 36.6% +/- 3.8% (p = 0.63) respectively. The degree of MCA asymmetry by Vpeak was 24.2% +/- 2.8% in Group I and 19.5% +/- 5.0% in Group II (p = 0.42), by Vmean 23.5% +/- 2.9% and 20.6% +/- 5.1% (p = 0.63) respectively. CVR in Group I was 26.1% +/- 6.1%, in Group II 29.0% +/- 6.7% (p = 0.65). The ophthalmic collateral pathway has no influence on hemispheric cerebral hemodynamics in patients with severe unilateral carotid stenosis.     

Feasibility of transcranial Doppler and single photon emission computed tomography in compound neuroactivation task

The aim of this study was to test feasibility of transcranial Doppler (TCD) and single photon emission computed tomography (SPECT) during compound neuroactivation task. The study was performed in 60 healthy right-handed volunteers. Cerebral blood flow velocity was measured by TCD in both middle cerebral arteries (MCA) at baseline and during computer game. The same stimulus and response pattern was used in 15 subjects that additionally underwent brain SPECT. Percentage differences between measurements were determined through quantitative result assessment. Both methods detected a statistically significant cerebral blood flow increase during neuroactivation. Correlation of TCD and SPECT showed statistically significant correlation only for the increase of cerebral blood flow velocity in the right MCA and for the right-sided cerebral blood flow increase, demonstrating that both methods partially measure similar cerebral blood flow changes that occur during neuroactivation. Comparison of TCD and SPECT showed TCD to be inadequately sensitive method for evaluation of cerebral blood flow during complex activation paradigm.     

Reduced middle cerebral artery velocity during cross-clamp predicts cognitive dysfunction after carotid endarterectomy

Transcranial Doppler (TCD) is a useful monitor that can be utilized during carotid endarterectomy (CEA). Cognitive dysfunction is a subtler and more common form of neurologic injury than stroke. We aimed to determine whether reduced middle cerebral artery (MCA) mean velocity (MV) predicts cognitive dysfunction and if so, whether a threshold of increased risk of cognitive dysfunction can be identified. One hundred twenty-four CEA patients were included in this observational study and neuropsychometrically evaluated preoperatively and 24 hours postoperatively. MCA–MV was measured by TCD and percentage of baseline during cross-clamp was calculated (MV_cross-clamp/MV_baseline). Patients with cognitive dysfunction had significantly lower MV during cross-clamp than those without cognitive dysfunction (33.1 ± 13.7 cm/s versus 39.6 ± 16.0 cm/s, p = 0.02). In the final multivariate model, each percent reduction in MV was significantly associated with greater risk of cognitive dysfunction (odds ratio [OR]: 0.05 [95% confidence interval {CI} 0.01–0.23], p < 0.001) while statin use was associated with lower risk (OR: 0.33 [95% CI 0.12–0.92], p = 0.03). Using receiver operator characteristic curve analysis, the Youden index identified 72% of baseline MV during cross-clamp as the cutoff of maximum discrimination. Significantly more patients with MV < 72% of baseline during cross-clamp exhibited cognitive dysfunction than patients with MV ⩾ 72% of baseline (74.1% versus 27.1%, p < 0.001). Reduced MCA–MV during cross-clamp is a predictor of cognitive dysfunction exhibited 24 hours after CEA. MCA–MV reduced to <72% of baseline, or a ⩾28% reduction from baseline, is the threshold most strongly associated with increased risk of cognitive dysfunction. These observations should be considered by all clinicians that utilize intraoperative monitoring for CEA.     

Cerebral hemodynamic response induced by the Tower of Hanoi puzzle and the Wisconsin Card Sorting test

Transcranial Doppler sonography (TCD) was applied in normal subjects to investigate the effect of prefrontal functions like the Tower of Hanoi (TOH) task and the Wisconsin Card Sorting test (WCST) on cerebral hemodynamics. In 20 healthy volunteers, left and right middle cerebral artery (MCA) and anterior cerebral artery (ACA) were insonated. The TOH task and the WCST were administered while cerebral blood flow velocity (CBFV) was registered. Each test was repeated once per artery pair. There was a visuomotor test to control the motor and visual stimulations. Three phases of CBFV time course were detected: an initial peak within 5 s, a following decrease within 25 s and a steady state beginning at 40 s. The TOH task, WCST and visuomotor tests had different mean CBFV during the initial peak (MCA: P<0.05; ACA: P<0.05) as well as for the decrease (ACA: P<0.01) and the steady state (MCA: P<0.01; ACA: P<0.01). The TOH showed an increased mean CBFV as compared with the WCST during the steady state (MCA: P<0.01; ACA: P<0.05). However, temporal modulation of mean CBFV during category shift of the WCST resulted in significantly increased values after category shift (MCA: P<0.001; ACA: P<0.01) as compared with CBFV before the category shift. These findings showed a different CBFV pattern during the TOH task and WCST than during the visuomotor test. In conclusion, TCD was able to assess CBFV in prefrontal functions, using a high resolution in time.     

Evaluation of cerebrovascular reactivity by ultrasonography in type 2 diabetic patients with hypertension

BACKGROUND: Cerebrovascular reactivity (CVR) reflects cerebrovascular reserve capacity, and cerebrovascular reactivity damage prognosticates a very high risk of stroke. OBJECTIVE: To evaluate CVR by detecting the increase rate of blood flow volume of middle cerebral artery (MCA) before and after breathholding in diabetic patients with hypertension, and observe the effects of hypertension on cerebrovascular reserve capacity of diabetic patients. DESIGN: Controlled observation. SETTINGS: Department of Function, Affiliated Hospital of Hebei University; Department of Special Diagnosis, the 202 Hospital of Chinese PLA. PARTICIPANTS: Inpatients or outpatients with type 2 diabetes mellitus (DM) or primary hypertension admitted to Departments of Gastroenterology and Cardiology, Affiliated Hospital of Hebei University and the 202 Hospital of Chinese PLA from April to December 2004 were involved in this experiment. Inclusive criteria: type 2 DM met the criteria of the report on diabetes diagnosis announced in 1999 by WHO expert committee, totally 88 patients were involved. Primary hypertension met the diagnosis criteria announced in 1999 by WHO/ISH, totally 42 patients were involved. Another group of 43 concurrent subjects who received physical examination served as controls. According to the disease condition, the involved patients were assigned into 3 groups: DM group (only diabetic patients), hypertension group (only hypertension patients) and DM complicated with hypertension group (diabetic patients with hypertension). Informed consent for the examination was obtained from all the involved subjects. METHODS: Before MCA of subjects was detected, bilateral carotid artery was routinely detected by high-frequency ultrasonography. Subjects were rejected when stenosis rate of unilateral internal carotid artery or common carotid artery ≥ 70%. Vessels were expanded with transcranial color Duplex Doppler by breath holding test for detecting vascular reactivity. Hypercapnia was created by BHT. The mean velocity and diameter of blood flow were detected under the quiescent condition and 25 s after breath holding with transcranial color-coded duplex sonography. The volume of blood flow of MCA was calculated according to the following formula: Volume of blood flow of MCA (mL/ min) = (the diameter of blood flow /2) 2×π×mean blood flow velocity×60. The increase rates of mean blood flow velocity and blood flow volume of patients with hypercapnia were calculated as compared with under the quiescent condition to evaluate cerebrovascular reactivity. MAIN OUTCOME MEASURES: Mean blood flow velocity, blood flow diameter and MCA blood flow volume as well as the increase rates of them. RESULTS: Among the 173 participates, 103 patients and 39 healthy controls were involved in the final analysis, and the other 31 dropped out due to not accomplishing the examination. ①Comparison of blood flow parameter of MCA under the quiescent condition: The mean blood flow velocity of DM complicated by hypertension group was significantly higher than that of DM group (P < 0.05) and control group (P < 0.05); The blood flow diameter of DM complicated by hypertension group was significantly smaller than that of control group (P < 0.01). Under the quiescent condition, significant difference was not found in the intergroup comparison of blood flow volume of MCA. ② Comparison of increase rate of blood flow parameter: In the DM group, hypertension group, DM complicated by hypertension group and control group, the increase rate of mean blood flow velocity of was （29.34±4.50）%,（29.35±4.35）%,（26.68±4.99）% and （30.99±3.54）%, respectively, the increase rate of blood flow volume of MCA was （35.32±5.08）%,（35.36±6.16）%,（31.78±7.11）% and（37.26±4.17）%, respectively, and the increase rate of blood flow diameter was （2.29±1.09）%,（2.27±0.95）%,（1.97±1.05）% and（2.36±0.46）%, respectively. The increase rate of mean blood flow velocity and that of blood flow volume of MCA in the DM complicated by hypertension group were significantly lower than those in the other 3 groups (P < 0.05). CONCLUSION: CVR is markedly lowered and cerebrovascular reserve capacity is damaged in diabetic patients with hypertension.     

Different Flow Patterns in Infarction of the Middle Cerebral Artery

Difficulties exist in distinguishing patients with currently recanalized mainstem occlusion of the middle cerebral artery (MCA) from branch occlusion. Thirty-five patients, 8 women and 27 men, at a mean age of 64 ± 15 (standard deviation) years, with clinical signs of infarction in the MCA territory confirmed by computed tomography (CT), were evaluated by repeated clinical and transcranial Doppler sonography within 2 days of the event, 2 to 5 days later, and at 2 weeks after admission. The quotient MCA 1/MCA C, derived to evaluate side differences, is defined as mean velocity (MV) in the MCA on the infarcted (I) side divided by MV in the MCA on the contralateral (C) side. Occlusion of the MCA was found in 13 of 35 patients at the first examination. A very high MV of 94 ± 6 em/sec with an abnormal turbulent flow pattern was found in 3 patients at the first examination, consistent with pseudostenosis after recanalization. The remaining 19 patients with a patent MCA had a lower MV in the affected side compared to the healthy side (37 ± 15 and 54 ± 20 em/sec, p < 0.001). Five (38%) of 13 patients with acute MCA mainstem occlusions demonstrated recanalization at the second examination, within 1 week after the onset of stroke, with a MV of 82 ± 44 em/sec and pulsatility index (PI) of 0.68 ± 0.38, which differed (p < 0.05) from the MV of 46 ± 19 em/sec and PI of 0.99 ± 0.20 in the remainder. The MCA 1/MCA C quotient revealed a difference (p < 0.01) between primarily patent vessels and recanalization at the second examination. A tendency to a better prognosis was found in originally patent or later recanalized vessels. Progression of neurological signs was noted in 3 (23%) of 13 patients with MCA occlusion and in 1 (4%) of 22 with nonoccluded MCAs.     

急性脑梗死各临床亚型患者的脑血管反应性的变化

目的 探讨急性脑梗死各临床亚型患者脑血管反应性(CVR)的变化.方法 将70例急性脑梗死患者分为3个亚组:动脉硬化性血栓形成性脑梗死(AI)组(22例)、腔隙性脑梗死(LI)组(33例)和心源性脑梗死(CI)组(15例).应用经颅多普勒超声(TCD)检测各组患者双侧大脑中动脉(MCA)的平均流速(Vm)、脉动指数(PI)、阻力指数(RI)指标,通过屏气试验测定屏气指数(BHI);并与20名正常对照组进行比较. 结果与正常对照组相比,AI组Vm、PI、RI均显著升高(P<0.05～0.01),BHI明显降低(P<0.01);LI组Vm、BHI均显著降低(均P<0.05);而CI组各参数与正常对照组相比差异无统计学意义. 结论急性脑梗死各亚组的CVR改变并不相同,AI、LI组CVR损害更为明显,CVR检测对急性脑梗死各亚型的血液动力学研究有重要意义.     

Tissue oxygen saturation and pulsatility index as markers for amnestic mild cognitive impairment: NIRS and TCD study

ObjectiveTo evaluate the utility of near-infrared spectroscopy (NIRS) and transcranial Doppler (TCD) parameters as potential markers for amnestic mild cognitive impairment (aMCI).MethodsBy means of NIRS and TCD, noninvasive and inexpensive technologies, we studied 21 patients with aMCI (10 M and 11 F, 70.2 ± 7.3 years) and 10 age matched healthy controls.ResultsBy means of NIRS, we found a significant mean decrease of tissue oxygen saturation of cortex microcirculation (TOI), – 27%, p < 0.0005, on the temporal–parietal cortex of both side compared to the controls. By means of TCD, we found a significant mean increase of pulsatility index (PI), p < 0.0007, of middle cerebral artery (MCA) of both side compared to the controls. Cerebrovascular risk factors were present in 81% of the aMCI patients.ConclusionsOur study reveals that the TOI reduction on the temporal-parietal cortex of both side and the increase of PI in both MCA are associated with a clinical diagnosis of aMCI patients.SignificanceThe reduction of TOI may be considered a new marker for aMCI, especially when combined with the increase of PI in MCA.