Evaluation of Cerebral Vasoreactivity by SPECT and Transcranial Doppler Sonography using the Acetazolamide Test

Vasoreactivity induced by acetazolamide in patients with vascular dementia versus Alzheimer's disease

Acetazolamide vasoreactive test measures the increment of cerebral blood flow caused by compensatory vasodilatation ability of cerebral vessels which can be detected by transcranial Doppler ultrasound (TCD). This study aimed to compare the vascular reactivity in patients with vascular dementia (VaD) and Alzheimer's disease (AD).

PATIENTS AND METHODS

AD and VaD patients were recruited from the King Chulalongkorn Hospital Dementia Clinic. Thai Mini-mental State Examination was used for dementia detection. AD and possible VaD were defined by NINCDS/ADRDA and NINDS-AIREN criteria. Patients with extracranial carotid artery stenosis >50% and intracranial artery stenosis were excluded. TCD examination was performed using DWL Multi Dop-T. TCD was performed on MCA with insonation depth between 45 and 60 mm. Baseline end diastolic velocity (EDV), mid systolic velocity (MSV) and peak systolic velocity (PSV) were recorded. The velocities were obtained at 2, 5, 10 and 20 min after acetazolamide (1000 mg) injection. Mean baseline velocities (Vo) and velocities after acetazolamide injection (Va) were compared. Percentage of mean increment velocities was calculated {[(Va-Vo)/Vo]x100%}. Percentage differences of mean velocity change from Vo to Va at each recorded minute were compared. SPSS for Windows version 11.5.0. was used.

RESULT

Nine AD (5 males) and 9 VaD (6 males) were selected. Average ages of VaD and AD groups were 66.11 years-old and 75.22 years-old respectively. Mini-mental State Examination (MMSE) score in VaD and AD were 21.13 and 19.00. Mean baseline EDV and MSV in VaD were higher than AD but mean PSV was lower. The percentage of velocity change after acetazolamide in AD was higher than VaD at 5, 10 and 20 min. However the differences were not statistically significant.

CONCLUSION

Acetazolamide vasoreactive test using TCD may be the additional criterion to differentiate VaD from AD. Further study with more number of subjects for the study or higher dose of acetazolamide may be needed to reveal the significant difference of vasoreactive response between VaD and AD patients.

Acetazolamide vasoreactivity evaluated by transcranial power harmonic imaging and Doppler sonography

BACKGROUND

Cerebral vasoreactivity (CVR) in the major cerebral arteries evaluated by transcranial Doppler sonography has shown some correlation with CVR in the brain tissue measured by other neuroradiological modalities. To clarify vasoreactive differences in the brain tissue and the major cerebral arteries, we have evaluated the relationship of acetazolamide (ACZ) CVR between transcranial ultrasonic power harmonic imaging (PHI) and color Doppler sonography (CDS), in cases ofparenchymal pathology with and without occlusive vascular lesions.

MATERIALS AND METHODS

The subjects were 31 stroke patients with intraparenchymal pathologies, 15 with (occlusive group) and 16 without (non-occlusive group) occlusive carotid and/or middle cerebral artery lesions. CVR based on values before/after ACZ (angle-collected CDS velocity in the middle and posterior cerebral arteries, PHI contrast area size, peak intensity, time to peak intensity), and correlation of CVR between PHI and CDS were compared between the side with and without lesions in both groups.

FINDINGS

(a) PHI CVR tended to be more disturbed than CDS CVR. CVR side differences were not significant. (b) CVR correlations between PHI and CDS were always lower in the pathological sides.

CONCLUSIONS

CVR in brain tissue evaluated by PHI is susceptible to disturbance in comparison with CDS, due to both parenchymal and vascular occlusive pathologies.

Dynamic autoregulation testing in patients with middle cerebral artery stenosis

BACKGROUND AND PURPOSE

Cross-spectral analysis (CSA) of spontaneous oscillations in cerebral blood flow velocity (CBFV) and arterial blood pressure is considered a sensitive and convenient method for dynamic autoregulation testing. So far, it has been unclear whether CSA can be used to assess stenoses of the intracranial arteries.

METHODS

This study for the first time applies CSA to 26 patients with low-, moderate-, and high-degree M1 stenoses and 14 normal control subjects. Using CSA, we studied spontaneous oscillations (M waves, 3 to 9 cpm; B waves, 0.5 to 3 cpm) in continuous recordings of transcranial Doppler of the middle cerebral artery and simultaneously recorded beat-to-beat blood pressure.

RESULTS

A gradual decrease in pulsatility indexes confirmed the increasing hemodynamic relevance of the stenoses. Compared with control subjects, M-wave phase shifts between CBFV and blood pressure were gradually reduced with increasing degree of M1 stenosis (control subjects, 44.6+/-21.1 degrees; high-degree stenosis, 16.7+/-19.5 degrees ). The phase relation between B waves in blood pressure and CBFV was shifted to positive values (low-degree stenosis, -9.7+/-108.4 degrees; high-degree stenosis, 50.9+/-43.8 degrees ).

CONCLUSIONS

Because B- and M-wave phase shifts seem to characterize the degree of autonomy of CBFV modulation, this study suggests that with increasing degree of M1 stenosis, the arteriolar function is impaired. It shows that CSA is of indicative use for the assessment of intracranial artery stenosis.

The transsylvian approach is "minimally invasive" but not "atraumatic"

OBJECTIVE

In light of the competition between microneurosurgery and alternative methods such as stereotactic radiosurgery, we tested the hypothesis that changes in the cerebral circulation after microneurosurgery are common among patients without evidence of cerebrovascular or neoplastic disease.

METHODS

Blood flow velocities (BFVs) were recorded with transcranial Doppler ultrasonography, before surgery and every other day after surgery, for a group of 50 patients who underwent transsylvian selective amygdalohippocampectomies for treatment of hippocampal sclerosis. Hexamethylpropylene amine oxime-single-photon emission computed tomographic testing, including acetazolamide testing of cerebrovascular reactivity, was performed during the second postoperative week for 20 of the 50 patients.

RESULTS

BFVs in basal arteries ipsilateral to the surgical approach increased significantly (P < 0.001) from preoperative baseline values of approximately 52 +/- 13 cm/s (mean +/- standard deviation) to values of approximately 86 +/- 27 cm/s on postoperative Day 3 and reached their maximal values of approximately 115 +/- 37 cm/s after a median of 7 days. BFVs in contralateral vessels exhibited a similar but somewhat attenuated pattern. Hexamethylpropylene amine oxime-single-photon emission computed tomography demonstrated ipsilateral regions of hypoperfusion in 100.0% of the cases and contralateral hypoperfusion in 80.0%. Cerebrovascular reactivity was impaired in 83.3% of the cases ipsilaterally and in 33.3% contralaterally.

CONCLUSION

A significant proportion of patients who undergo microneurosurgical procedures develop bilateral alterations of their cerebral circulation. The elevations in mean BFV values represent cerebral vasospasm. Because these changes remain asymptomatic for the majority of patients, the transsylvian approach can be considered "minimally invasive" but not "atraumatic." Alternative surgical routes and alternative treatment modalities should be investigated in a similar manner.

Influence of acetazolamide and CO2 on extracranial flow volume and intracranial blood flow velocity

BACKGROUND AND PURPOSE

The vasomotor response can be tested by means of transcranial Doppler sonography. If a constant vessel diameter is assumed, the flow velocity changes will reflect blood flow volume changes. This hypothesis is difficult to verify. Simultaneous assessment of intracranial flow velocity and extracranial flow volume changes may solve this problem.

METHODS

We tested vasomotor response in 32 volunteers (age, 42+/-18 years) with 5% CO2. Acetazolamide (1 g) was tested in 15 volunteers (age, 28+/-8 years). To evaluate drug-dependent flow changes in the external carotid artery territory, acetazolamide was administered in 7 patients with unilateral occlusion of the internal carotid artery without evidence of collateralization through the ophthalmic artery (age, 67+/-12 years). Simultaneous recording included measurements of flow volume in the common carotid arteries (M-mode color duplex system) and flow velocity in the middle cerebral arteries.

RESULTS

With CO2 and acetazolamide, intracranial flow velocity increased by 31% and 39%, respectively, with a simultaneous increase of common carotid artery flow volume of 47% and 50%, respectively. No change in extracranial flow volume was observed in patients with an occluded internal carotid artery.

CONCLUSIONS

These data show not only the expected increase of flow velocity in the middle cerebral artery but also suggest an increase in cross-sectional vessel diameter of 6% and 4% with CO2 and acetazolamide, respectively. It remains unresolved whether this observation is due to a direct effect of the drug on the vessel walls or is simply pressure dependent.

Acetazolamide induced myocardial ischemia in patients with severe coronary artery disease

Acetazolamide (ACZ)-augmented brain SPECT is commonly used for evaluating cerebral vascular reserve in patients with cerebrovascular disease. ACZ may cause myocardial ischemia in patients with coronary artery disease. To evaluate the risk of induction of myocardial ischemia with ACZ-augmented myocardial SPECT, we performed combined ACZ-augmented Tl-201 myocardial SPECT (ACZ-myo SPECT) with Tc-99m HMPAO brain SPECT in patients with severe coronary artery disease.

METHODS

Nine patients underwent combined ACZ-myo SPECT with Tc-99m HMPAO brain SPECT. (1) For qualitative analysis, SPECT images were divided into 13 segments to calculate the total defect scores. (2) Six ROIs were placed on the slices in the myocardial SPECT short-axis images and the regional uptake ratio was obtained as the ratio of the mean counts in the myocardium to the maximal count in the slice. The total defect score and regional uptake ratio of ACZ-myo SPECT were compared with those of early and delayed dipyridamole Tl-201 myocardial SPECT (DP-Tl SPECT) images.

RESULTS

(1) In the 21 coronary artery territories with coronary stenosis > or = 75%, the total defect score in ACZ-myo SPECT, early and delayed DP-Tl SPECT images were 3.52 +/- 4.14*, 4.19 +/- 4.65* and 2.25 +/- 3.34, respectively (*: p < 0.05 vs. delayed DP-Tl SPECT images). (2) In 44 of 54 ROIs with coronary stenosis > or = 75%, the regional uptake ratio of ACZ-myo SPECT, early and delayed DP-Tl SPECT images were 0.670 +/- 0.166**, 0.677 +/- 0.194**, 0.721 +/- 0.178, respectively (**: p < 0.01 vs. delayed DP-Tl SPECT images). Systolic blood pressure fell at 11 min after ACZ infusion without electrocardiographic ST-T changes or chest pain.

CONCLUSION

As ACZ has the potential to cause myocardial ischemia, ACZ-augmented brain SPECT should be performed with caution in patients with severe coronary artery disease associated with cerebrovascular disease.