99mTc-HMPAO-SPECT with acetazolamide challenge to detect hemodynamic compromise in occlusive cerebrovascular disease

Deep learning-based interpretation of basal/acetazolamide brain perfusion SPECT leveraging unstructured reading reports

PURPOSE

Basal/acetazolamide brain perfusion single-photon emission computed tomography (SPECT) has been used to evaluate functional hemodynamics in patients with carotid artery stenosis. We aimed to develop a deep learning model as a support system for interpreting brain perfusion SPECT leveraging unstructured text reports.

METHODS

In total, 7345 basal/acetazolamide brain perfusion SPECT images and their text reports were retrospectively collected. A long short-term memory (LSTM) network was trained using 500 randomly selected text reports to predict manually labeled structured information, including abnormalities of basal perfusion and vascular reserve for each vascular territory. Using this trained LSTM model, we extracted structured information from the remaining 6845 text reports to develop a deep learning model for interpreting SPECT images. The model was based on a 3D convolutional neural network (CNN), and the performance was tested on the other 500 cases by measuring the area under the receiver-operating characteristic curve (AUC). We then applied the model to patients who underwent revascularization (n = 33) to compare the estimated output of the CNN model for pre- and post-revascularization SPECT and clinical outcomes.

RESULTS

The AUC of the LSTM model for extracting structured labels was 1.00 for basal perfusion and 0.99 for vascular reserve for all 9 brain regions. The AUC of the CNN model designed to identify abnormal perfusion was 0.83 for basal perfusion and 0.89 for vascular reserve. The output of the CNN model was significantly improved according to the revascularization in the target vascular territory, and its changes in brain territories were concordant with clinical outcomes.

CONCLUSION

We developed a deep learning model to support the interpretation of brain perfusion SPECT by converting unstructured text reports into structured labels. This model can be used as a support system not only to identify perfusion abnormalities but also to provide quantitative scores of abnormalities, particularly for patients who require revascularization.

Characteristics of cerebral hemodynamics assessed by CT perfusion in moyamoya disease

Due to the recent development of multidetector row computed tomography (CT), hemodynamic parameters can now be conveniently obtained with CT perfusion. The purpose of this study is to characterize the hemodynamic parameters of CT perfusion in moyamoya disease, and to discuss the differences in collateral circulation between moyamoya disease and atherosclerotic disease. A total of 16 hemispheric sides of 15 patients with moyamoya disease and 10 hemispheric sides of 9 patients with atherosclerotic disease who underwent bypass surgery were included. CT perfusion was performed with ¹²³I-IMP SPECT. Cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) values obtained by CT perfusion using standard singular value decomposition as the deconvolution algorithm in moyamoya disease were calculated. Preoperative values of these parameters were compared with those of atherosclerotic disease. Then, the postoperative changes of these parameters were analyzed. In the impaired side, CBF as measured by CT perfusion was correlated with that measured by ¹²³I-IMP SPECT. In moyamoya disease, CBV as measured by CT perfusion was significantly increased compared to in atherosclerotic disease, yet CBF was significantly decreased in atherosclerotic disease. Postoperatively, the asymmetry ratios of MTT were significantly improved, especially in atherosclerotic disease compared with moyamoya disease. On CT perfusion, the parameters included transit time and arrival time. CBV increase in moyamoya disease and postoperative improvement of MTT, especially in atherosclerotic disease, were unique characteristics in each. This might be due to the difference of collateral circulation and compensatory mechanisms between moyamoya disease and atherosclerotic disease.

Perfusion computed tomography evaluation of cerebral hemodynamic impairment in patients with unilateral chronic steno-occlusive disease: a comparison with the acetazolamide challenge 99mTc-hexamethylpropyleneamine oxime single-photon emission computed tomography

PURPOSE

The purpose of this study was to determine which pefusion computed tomography (PCT) parameter is the most valid predictor of cerebral vascular reserve (CVR) as determined by Tc-hexamethylpropyleneamine oxime single-photon emission computed tomography (SPECT).

METHODS

Single-photon emission computed tomography with acetazolamide challenge and PCT were used in 23 patients with unilateral steno-occlusive vascular disease. After coregistration of the PCT and SPECT images, we assessed the relationship between the PCT parameters and SPECT findings and the predictive values of the PCT parameters for decreased CVR.

RESULTS

All PCT parameters of cerebral blood flow, cerebral blood volume, and mean transit time (MTT) were significantly correlated with SPECT regional cerebral blood flow ratios (P < 0.01). The MTT values more strongly correlated with acetazolamide effect than with cerebral blood volume or cerebral blood flow (P < 0.001). The MTT difference (values in the pathological hemisphere minus the values in the contralateral hemisphere) was a threshold of 1.5 seconds, with a sensitivity of 88% and a specificity of 70% for predicting decreased CVR.

CONCLUSION

Mean transit time is the most predictive parameter for assessing decreased CVR in patients with unilateral steno-occlusive vascular disease.

Cerebrovascular reactivity in depressed patients without vascular risk factors

INTRODUCTION

Cerebrovascular reactivity (CVR) seems to be gaining importance as a prognostic factor for stroke risk. CVR reflects the compensatory dilatory capacity of cerebral arterioles to a dilatory stimulus; this mechanism plays an important role in maintaining a constant cerebral blood flow. Evaluating factors that influence CVR will help prevention or early detection of cerebrovascular disease (CVD). In this study we aimed to measure the CVR in vascular-risk free depressed individuals so as to evaluate the effect depression has on CVR and hence its role as a stroke risk factor.

METHODS

Using acetazolamid (ACZ) stimulation, CVR was assessed with a transcranial Doppler ultrasound in 25 non-smoking depressed patients (average age: 48.48 +/- 14.40) and in 25 healthy non-smoking controls (average age: 46.76 +/- 13.69) by calculating the difference between the maximal mean blood flow velocity at baseline and the maximal mean blood flow velocity after ACZ stimulation.

RESULTS

Basal Cerebral Blood flow in Patients was 50.6 cm/s (SD: 11.6) versus controls 52.80 cm/s (SD: 12.70) whereas after stimulation maximal blood flow velocity was 72.64 cm/s (SD: 15.75) in patients versus 80.20 cm/s (SD: 18.43) in controls. In an analysis of covariance we found that cerebrovascular reactivity was significantly reduced in the vascular-risk free depressed sample. Age had a significant influence whereas gender did not.

DISCUSSION

Major Depression appears to decrease cerebrovascular reactivity supporting the idea of increased risk for stroke in depressed patients. The mechanisms leading to this phenomenon and its subtle subgroup differences should be further investigated.

Correlative assessment of cerebral blood flow obtained with perfusion CT and positron emission tomography in symptomatic stenotic carotid disease

Twelve patients with ICA stenosis underwent dynamic perfusion computed tomography (CT) and positron emission tomography (PET) studies at rest and after acetazolamide challenge. Cerebral blood flow (CBF) maps on perfusion CT resulted from a deconvolution of parenchymal time-concentration curves by an arterial input function (AIF) in the anterior cerebral artery as well as in both anterior choroidal arteries. CBF was measured by [(15)O]H(2)O PET using multilinear least-squares minimization procedure based on the one-compartment model. In corresponding transaxial PET scans, CBF values were extracted using standardized ROIs. The baseline perfusion CT-CBF values were lower in perfusion CT than in PET (P>0.05). CBF values obtained by perfusion CT were significantly correlated with those measured by PET before (P<0.05) and after (P<0.01) acetazolamide challenge. Nevertheless, the cerebrovascular reserve capacity was overestimated (P=0.05) using perfusion CT measurements. The AIF selection relative to the side of carotid stenosis did not significantly affect calculated perfusion CT-CBF values. In conclusion, the perfusion CT-CBF measurements correlate significantly with the PET-CBF measurements in chronic carotid stenotic disease and contribute useful information to the evaluation of the altered cerebral hemodynamics.

Single-Photon Emission CT Imaging in Acute Stroke

Single-photon emission CT (SPECT) is an underused noninvasive imaging tool for the management of patients who have acute or chronic ischemia. SPECT was introduced in the late 1970s and is a proven, cost-effective means for the evaluation of regional cerebral blood flow and cerebrovascular reserve. Evaluation of cerebral blood flow using SPECT has become more accessible with the commercial availability of tracers that cross the blood-brain barrier and are retained by cells of the central nervous system.

Acetazolamide as a vasodilatory stimulus in cerebrovascular diseases and in conditions affecting the cerebral vasculature

Pathologic processes affecting the brain vessels may damage cerebral vasodilatory capacity. Early detection of cerebral dysfunction plays an important role in the prevention of cerebrovascular diseases. In recent decades acetazolamide (AZ) has frequently been used for this purpose. In the present work the mechanism of action and the previous studies are reviewed. The authors conclude that AZ tests are useful in cerebrovascular research. Further investigations are recommended to prove how impaired reserve capacity and reactivity influence the stroke risk in patients and whether these tests may indicate therapeutic interventions.

Aspirin or amiloride for cerebral perfusion defects in cocaine dependence

Cocaine dependent (CD) patients have regional cerebral blood flow (rCBF) deficits that may be related to occlusion of blood vessels by vasoconstriction and abnormal platelet aggregation. This study determined whether aspirin, which reverses platelet aggregation, or amiloride, a vasodilator, significantly reversed this rCBF hypoperfusion. This 1-month randomized trial compared clusters of voxels with significant hypoperfusion in recently abstinent CD patients after aspirin (325 mg daily), amiloride (10 mg daily) or placebo treatment. Forty-nine primary CD patients and 18 non-drug abusing controls were compared using single photon emission computed tomography (SPECT) neuroimaging with 99mTc-hexamethyl-propyleneamine-oxime and statistical parametric mapping (SPM). Platelet aggregation to adenosine diphosphate (ADP) was examined after treatment to determine whether rCBF improvement was related to decreased platelet aggregation. Following treatment, areas of hypoperfusion were improved with amiloride, unchanged with aspirin, and worsened with placebo in comparison to baseline levels. Platelet aggregation after ADP showed no significant change during the month, but reduced rCBF significantly improved after 1-month treatment with amiloride compared with placebo and cocaine abstinence alone.

Fully automated quantification of regional cerebral blood flow with three-dimensional stereotaxic region of interest template: validation using magnetic resonance imaging--technical note

The previously reported three-dimensional stereotaxic region of interest (ROI) template (3DSRT-t) for the analysis of anatomically standardized technetium-99m-L,L-ethyl cysteinate dimer (99mTc-ECD) single photon emission computed tomography (SPECT) images was modified for use in a fully automated regional cerebral blood flow (rCBF) quantification software, 3DSRT, incorporating an anatomical standardization engine transplanted from statistical parametric mapping 99 and ROIs for quantification based on 3DSRT-t. Three-dimensional T2-weighted magnetic resonance images of 10 patients with localized infarcted areas were compared with the ROI contour of 3DSRT, and the positions of the central sulcus in the primary sensorimotor area were also estimated. All positions of the 20 lesions were in strict accordance with the ROI delineation of 3DSRT. The central sulcus was identified on at least one side of 210 paired ROIs and in the middle of 192 (91.4%) of these 210 paired ROIs among the 273 paired ROIs of the primary sensorimotor area. The central sulcus was recognized in the middle of more than 71.4% of the ROIs in which the central sulcus was identifiable in the respective 28 slices of the primary sensorimotor area. Fully automated accurate ROI delineation on anatomically standardized images is possible with 3DSRT, which enables objective quantification of rCBF and vascular reserve in only a few minutes using 99mTc-ECD SPECT images obtained by the RVR method.

Cerebral haemodynamic aspects of severe carotid stenosis: asymptomatic vs symptomatic

OBJECTIVES

to compare cerebral haemodynamics in patients with asymptomatic and symptomatic severe (> or =70%) internal carotid artery (ICA) stenosis.

METHODS

we assessed 195 consecutive patients, 116 with asymptomatic carotid stenosis (ACS) and 79 with symptomatic carotid stenosis (SCS). Using transcranial Doppler we assessed cerebral vasoreactivity (CVR) following acetazolamide test, the middle cerebral artery flow velocity ratio after/before carotid clamping (mv-MCA ratio), and the carotid back pressure (CBP) during crossclamping.

RESULTS

no significant differences between the two groups were demonstrated regarding CVR (47 vs 39%), mv-MCA ratio (50 vs 52%), or CBP (36 vs 44 mmHg). However, in patients with contralateral ICA occlusion all three variables were significantly lower as compared to patients with patent contralateral ICA. Also patients who needed a shunt during surgery had significantly lower values of mv-MCA ratio and CBP. Patients who suffered peri-operative neurologic deficits (n=6; 3%) did not differ from patients who had an uneventful course.

CONCLUSIONS

clinical state of ICA stenosis is independent of cerebral haemodynamics. Occluded contralateral ICA is more important for predicting cerebral ischaemia caused by carotid clamping. Finally, none of the haemodynamic parameters showed predictive value for peri-operative neurologic morbidity.

Cerebrovascular reactivity to acetazolamide in alert patients with cerebral infarction: usefulness of first-pass radionuclide angiography using 99m Tc-HMPAO in monitoring cerebral haemodynamics

Cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) were studied in 75 patients with cerebral infarction. All patients were alert with the symptoms of hemiparesis and/or aphasia, and were divided into two groups: 42 patients had occlusion or stenosis of >75% at the internal carotid artery or main trunk of middle cerebral artery; and 33 patients did not. Hemispheric mean CBF was measured by performing first-pass radionuclide angiography using 99mTc-hexamethylpropylene amine oxime. CVR was measured as the percentage change from the baseline mean CBF value after the administration of 500 mg acetazolamide. The CVR in both groups was significantly impaired (5.2+/-6.3%, P<0.001 and 7.7+/-6.1%, P<0.01, respectively) compared with normal controls (14.7+/-3.3%), although the mean CBF was not significantly reduced compared with age-matched controls. In the 12 patients with unilateral carotid occlusion, five patients with good collateral flow via the anterior communicating artery showed preserved CVR (11.0+/-7.8%), but those without did not (1.6+/-7.0%). CVR is impaired in alert patients with cerebral infarction, although the mean CBF is not reduced, and good collateral flow via the anterior communicating artery in patients with carotid occlusion may be a sign of well-preserved haemodynamic status.

Relationship between depression and cerebrovascular disease: conceptual issues

OBJECTIVES

The association between cerebrovascular disease (CVD) and depression has been well described, but our understanding of various aspects of the relationship between these two disorders remains limited.

METHOD

Based on a selective literature review, this paper examines empirical evidence and discusses conceptual issues concerning hierarchical, interactive, and co-morbid relationships between CVD and depression.

RESULTS

The concept of vascular depression minimizes the importance of the contribution of psychosocial factors. The interactive and co-morbid relationships have been largely neglected in psychiatric research. There is evidence that depression may increase the risk of CVD morbidity in patients with vascular disease and delay recovery in stroke patients, implying an interactive relationship. The concurrent existence of these two disorders based on common etiological factors such as genetic vulnerability, alcoholism and personality traits seems plausible.

CONCLUSIONS

A modified comorbidity model may guide investigation into the hierarchical, interactive and common etiological relationships between CVD and depression.

Changes in cerebral blood flow and vasoreactivity in response to acetazolamide in patients with transient global amnesia

OBJECTIVE

Previous reports about changes in cerebral blood flow (CBF) in transient global amnesia disclosed decreased flow in some parts of the brain. However, CBF analyses in most reports were qualitative but not quantitative. The purpose of this study was to determine changes in CBF in transient global amnesia.

METHODS

The CBF was measured and the vasoreactive response to acetazolamide was evaluated in six patients with transient global amnesia using technetium-99m hexamethylpropylene amine oxime single-photon emission computed tomography (SPECT). The CBF was measured during an attack in two patients and soon after an attack in the other four. About one month later, CBF was re-evaluated in each patient.

RESULTS

Two patients examined during an attack and one patient examined five hours after an attack had increased blood flow in the occipital cortex and cerebellum. Three patients examined at six to 10 hours after an attack had decreased blood flow in the thalamus, cerebellum, or putamen. These abnormalities of blood flow almost disappeared in all patients one month after onset. The vasodilatory response to acetazolamide, which was evaluated initially using SPECT, was poor in areas of increased blood flow. By the second evaluation of CBF with acetazolamide, the vasodilatory response had returned to normal.

CONCLUSIONS

In a patient with transient global amnesia, CBF increased in the vertebrobasilar territory during the attack and decreased afterwards. The vasodilatory response to acetazolamide may be impaired in the parts of the brain with increased blood flow. It is suggested that transient global amnesia is distinct from migraine but may share the same underlying mechanism.

Noninvasive quantitative measurements of regional cerebral blood flow using technetium-99m-L,L-ECD SPECT activated with acetazolamide: quantification analysis by equal-volume-split 99mTc-ECD consecutive SPECT method

Resting- and acetazolamide (Acz)-activated-regional cerebral blood flow (rCBF) measurements were performed by consecutive single-photon emission computed tomography (SPECT) studies before and after Acz administration using equal-volume-split technetium-99m-L,L-ethyl cysteinate dimer. Quantitative rCBF images were converted from qualitative axial SPECT images by the application of Patlak plot graphical analysis with radionuclide angiography and Lassen's linearization correction. Total time span required for this study was 53 minutes. The unaffected side of 37 studies with unilateral vascular lesions and 45 studies without apparent vascular lesions showed 132 +/- 17% and 140 +/- 15% increase of mean CBF (mCBF), respectively, under Acz administration. Comparing these values, the Acz-activated rCBF increases of less-affected and affected hemispheres of 23 studies with bilateral vascular lesions (116 +/- 13% and 113 +/- 12%, respectively) was lower with high statistical significance (P < 0.001). For the other 20 cases, physiologic saline was administered instead of Acz. This group showed no changes in mCBF under placebo administration (after placebo/baseline; 100 +/- 6%). Acetazolamide-activated rCBF increase was recognized clearly and easily using quantitative images. This noninvasive method is easy to perform and may be helpful to detect regional abnormalities of hemodynamic reserve in cerebrovascular diseases.

Assessment of cerebrovascular reactivity by dynamic susceptibility contrast-enhanced MR imaging

In patients with cerebrovascular disease the acetazolamide (ACZ) test is performed to evaluate the decrease in cerebral perfusion pressure (CPP) through the investigation of the vasomotor reactivity (VMR). This latter is currently assessed with ACZ with several methods. Recently, magnetic resonance imaging (MRI) techniques have been developed that are sensitive to stimulus-induced changes in blood flow. Dynamic susceptibility contrast material-enhanced gradient-echo MRI techniques (DSC-MRI) might be an attractive tool to assess VMR. We aimed to test the ability of DSC-MRI in the assessment of VMR. Relative hemodynamic parameters rCBV, MTT, and rCBF were evaluated at baseline after the first injection of gadopentetate dimeglumine and 10 min after the intravenous administration of ACZ (1 g) with a second bolus of contrast agent. Assessment of hemodynamic parameters was performed over the whole hemisphere and also within regions of interest. The significances of the mean differences, before and after ACZ, were assessed with repeated-measures ANOVA with two within factors: laterality (right-left) and ACZ. DSC-MRI with ACZ test was performed in ten healthy controls (aged 51.4+/-16.2 years). The cerebral hemispheric ratio for the three parameters (cerebral blood volume (CBV), mean transit time (MTT), and cerebral blood flow (CBF)) ranged between 1.01 and 1.03. The mean gray matter-to-white matter ratio for CBV, CBF and MTT were 2.44, 2.41 and 1.05, respectively. As the laterality effect was not significant, left and right hemispheric values were averaged. A significant increase of all hemodynamic parameters was observed after ACZ (P<0.01-0.001). The same changes for CBV, CBF and MTT were observed after ACZ according to the regions of interest (P<0.006-0.015). DSC-MRI is a non-invasive method which enables the assessment of VMR. This technique may be added to any conventional MRI in order to detect a hemodynamic impact of an ICA stenosis. Therefore, it might be useful in determining the appropriate management when the indication for surgical versus medical therapy is in question.

Changes in local cerebral blood flow by neuroactivation and vasoactivation in patients with impaired cognitive function

Imaging of local cerebral blood flow (lCBF) may serve as an important supplementary tool in the aetiological assessment of dementias. In early or preclinical disease, however, there are less characteristic changes in lCBF. In the present study it was investigated whether vasoactivation or neuroactivation may produce more pronounced local lCBF deficits. Local CBF was investigated by using technetium-99m hexamethylpropylene amine oxime and single-photon emission tomography (SPET) in 80 patients (50 with mild cognitive impairment and 30 with dementia of Alzheimer type (DAT), all without evidence of cerebrovascular disease) at rest (baseline) and during activation. In 31 studies patients underwent vasomotor activation with acetazolamide, while 62 studies were performed under cognitive challenge (neuroactivation by labyrinth task). Cortical activity relative to that of cerebellum increased significantly in a right temporal region and tended to increase in other cortical regions upon vasoactivation. In contrast, neuroactivation reduced cortical activity relative to that of cerebellum in several left and right temporal and in left parietal regions. Visual classification of SPET images of patients with probable DAT by three observers resulted in a reduction of the number of definitely abnormal patterns from 9/12 to 4/12 by vasoactivation and an increase from 10/18 to 15/18 by neuroactivation. Correspondingly, abnormal ratings in patients with mild cognitive dysfunction were reduced from 7/19 to 5/19 by vasoactivation and were increased from 12/21 to 18/21 by neuroactivation. In conclusion, vasoactivation does not enhance local relative perfusion deficits in patients with cognitive impairment of non-vascular aetiology, whereas neuroactivation by labyrinth task produces more pronounced local flow differences and enhances abnormal patterns in lCBF imaging.

Omental transplantation using a superficial temporal artery previously used for encephaloduroarteriosynangiosis

BACKGROUND

Childhood moyamoya disease is a chronically progressive cerebrovascular occlusive disease affecting the territories of the anterior, middle, and posterior cerebral arteries. Surgery used in treatment of moyamoya disease to vascularize the brain include direct and indirect anastomoses.

METHODS

Intracranial omental transplantation (OMT) was performed using a branch of the superficial temporal artery (STA) that had been used previously for encephaloduroarteriosynangiosis (EDAS) in five children with moyamoya disease. All five children continued to have paraparetic transient ischemic attacks (TIAs), urinary incontinence, and/or progressive mental retardation even after EDAS and/or STA-middle cerebral artery (MCA) anastomosis and encephalomyosynangiosis (EMS) to the territory of the MCA. Previously performed EDAS gave insufficient collaterals to the territory of the MCA in four of the five patients and sufficient collaterals to the territory of the MCA in the remaining patient. OMT was performed after stripping of a branch of the STA used in EDAS that gave insufficient collaterals to the brain in the former four patients; and the latter patient was performed using a parietal branch of the STA distal to the distal burr hole drilled in the previous EDAS.

RESULTS

OMT resulted in marked improvement in neurologic conditions in all five patients. Four of the five patients suffered no TIAs postoperatively, while the remaining patient still had TIAs but at a markedly decreased frequency.

CONCLUSIONS

In summary, OMT using a branch of the STA used in previously performed EDAS is required for patients with moyamoya disease who continue to manifest paraparesis, urinary incontinence, and/or progressive mental retardation even after multiple EDAS.

Clinical significance of the ophthalmic artery in carotid artery disease

A total of 141 subjects with tight stenosis (> or = 75%) or occlusion of internal carotid artery were followed up at intervals 3-6 months regularly for 40 +/- 16 months. The direction of ophthalmic artery flow was used as a parameter of risk indicator on cerebral ischemic events. Eleven patients with bilateral carotid tight stenosis/occlusion were excluded in the analysis. Thus, the 130 carotid arteries were divided into three groups: (1) carotid artery with ipsilateral hemispheric TIA or stroke (85 patients), (2) carotid arteries with contralateral hemispheric TIA/stroke or VBI (15 patients), and (3) carotid arteries of asymptomatic patients (30 patients). The symptomatic carotid artery group (group 1) had significantly more often reversed ophthalmic flow than the other two groups (group 2 and 3, p < 0.001). During follow-up prospectively for four years, 41 patients had cerebral ischemic events, three had cardiac ischemic events and six died of malignancy. Patients with reversed OA flow had more often subsequent cerebral ischemic events than those with forward flow (27 vs 14, p = 0.010). However, the difference remained significant only in the asymptomatic patients (group 3, 4 vs 0, P < 0.001), not for groups 1 and 2, after further analysis. Our work supported that the clinical role of ophthalmic artery collateral varied between asymptomatic and symptomatic patients.

Percutaneous transluminal angioplasty in the treatment of atherosclerotic disease of the anterior cerebral circulation and hemodynamic evaluation

Nineteen patients between 56 and 76 years of age with clinically symptomatic atherosclerotic stenotic lesions at or distal to the C-5 segment in the carotid arterial system underwent percutaneous transluminal angioplasty (PTA). The 19 patients had a total of 19 stenotic lesions, including two lesions in the C-5 segment, three in the C-4 segment, and three in the C-2 segment of the carotid artery, six in the M1 segment and three in the M2 segment of the middle cerebral artery, and two in the A2 segment of the anterior cerebral artery. Both prior to and more than 6 months after PTA, angiograms were performed and cerebral perfusion was measured using 99mTc-hexamethyl-propyleneamine-oxime single-photon emission computerized tomography, before and after the administration of 10 mg/kg acetazolamide. Percutaneous transluminal angioplasty could be performed in 13 (68.4%) of the 19 patients. The mean degree of stenosis (+/- standard deviation) was 83.1% +/- 8.6% before PTA, but only 35.8% +/- 17.3% on the follow-up angiograms. Restenosis was detected in follow-up angiograms in five (38.5%) of the 13 patients. Seven of the 13 patients exhibited improvement in their neurological condition after PTA and had shown subnormal cerebral perfusion and subnormal vasodilatory response to administration of acetazolamide prior to undergoing PTA. On the other hand, the remaining six patients exhibited no improvement in neurological condition after PTA, and four of these patients (66.7%) had shown normal perfusion and five (83.3%) had shown normal vasodilatory response to administration of acetazolamide prior to undergoing PTA. These findings suggest that PTA may be indicated for patients with atherosclerotic stenotic lesions in the anterior cerebral circulation who have subnormal cerebral perfusion and low vasodilatory response to administration of acetazolamide.

A study of acetazolamide-induced changes in cerebral blood flow using 99mTc HMPAO SPECT in patients with cerebrovascular disease

For semiquantification of SPECT studies we tried to calculate cerebral 99mTc-HMPAO uptake related to injected dose and estimated brain volume. The method was applied to SPECT investigations of 27 patients who had at least one ischaemic attack and a confirmed 80-100% stenosis of the corresponding internal carotid artery (ICA). Vascular reactivity was tested by parenteral administration of acetazolamide (AZ). Increase in HMPAO uptake after AZ was evident in both hemispheres, although the increase (AZ effect) was significantly lower in the affected hemisphere (+24% versus +28%). No interhemispheric uptake differences were seen in patients with largely normal SPECT studies, although local asymmetries in HMPAO deposition were visible. Patients with low density lesions on CT and with a well-demarcated lesion in the same location on SPECT revealed interhemispheric uptake differences, with lower uptake on the affected side. This was not due solely to alterations in the lesion, but also to reduced HMPAO uptake and AZ effect in the surrounding area. The AZ effect showed no correlation with angiographic findings, indicating no major haemodynamic influence of the ICA stenosis on cerebral hemisphere perfusion. Calculated cerebral HMPAO uptake changes after AZ administration were in good accordance with absolute cerebral blood flow measurements, and made interindividual comparisons possible. However, as changes in the area around an infarct or local reduction in vascular reserve may not be reproduced adequately by uptake calculations, visual inspection is still necessary.

Percutaneous transluminal angioplasty for severe stenosis of the posterior cerebral artery: case report

The Stealth dilation catheter was used for the intravascular treatment of a patient who had hemodynamically significant stenosis of the posterior cerebral artery and had a history of recurrent transient ischemic attacks associated with right hemiparesis and ipsilateral hemianopia dating from March 1993. Cerebral perfusion studies prior to and after the intravenous administration of acetazolamide demonstrated regions of moderately low perfusion and low hemodynamic reserve in the territories of the left middle and posterior cerebral arteries. Cerebral angiograms demonstrated severe stenosis of the left posterior cerebral artery and occlusions of both middle cerebral arteries, which had leptomeningeal anastomoses with the posterior cerebral arteries. Percutaneous transluminal angioplasty (PTA) was performed using the Stealth catheter on the stenotic segment of the left posterior cerebral artery after left superficial temporal artery-middle cerebral artery anastomosis. The patient manifested marked improvement in her neurologic condition just after PTA, in association with marked increase in cerebral perfusion and hemodynamic reserve in the territories of the left middle and posterior cerebral arteries. We have presented evidence that PTA can be used to treat patients with stenosis of the first segment of the posterior cerebral artery and hemodynamic compromise in the territory that artery supplies.

Acetazolamide reactivity on 123I-IMP single photon emission computed tomography in patients with major cerebral artery occlusive disease: correlation with positron emission tomography parameters

Single photon emission computed tomography (SPECT) with acetazolamide challenge has increasingly been used for evaluating hemodynamic reserve in stroke patients. The accuracy of this test, however, has not been validated with positron emission tomography (PET). In 14 patients who had occlusive disease of the internal carotid artery or the trunk of the middle cerebral artery (MCA) with minimal or no infarction on computed tomography (CT) and magnetic resonance imaging (MRI), we compared acetazolamide reactivity on SPECT with N-isopropyl-p-[123I]-iodoamphetamine to hemodynamic parameters determined with gas inhalation labeled 15O steady-state PET studies. The asymmetry index (AI)--i.e., the percentage of the activity rate of the ischemic MCA territory versus the contralateral one, was determined by SPECT. Acetazolamide reactivity expressed as delta AI, or change in AI after acetazolamide challenge, was significantly lower in seven patients than -8.4%, the lower limit of the 95% confidence interval for the normal reactivity. Values of ipsilateral CBF, cerebral blood volume (CBV)/CBF, and oxygen extraction fraction (OEF) and contralateral OEF were significantly different between patients with normal and reduced acetazolamide reactivity. Values of delta AI were correlated with OEF (r = -0.87; p < 0.001) and CBV/CBF (r = -0.56; p < 0.05). All patients with OEF > 0.52, the mean + 2 SD calculated from five normal volunteers, also had reduced acetazolamide reactivity, while the patients with normal OEF values had normal reactivity. The present study has demonstrated that SPECT studies with an acetazolamide challenge can detect the Stage II hemodynamic failure.

Carotid endarterectomy for unstable and compelling neurologic conditions: do results justify an aggressive approach?

PURPOSE

In a retrospective study the outcome of 70 carotid endarterectomies (CEA) in 68 patients with neurologically unstable conditions or anatomically compelling findings on carotid angiography was examined to more accurately identify patients who might benefit from CEA in this setting.

METHODS

Out of a total of 1734 CEAs performed from 1978 to 1992, five groups of patients were selected: group A, stroke in evolution with tight stenosis (n = 5); group C, crescendo transient ischemic attacks (CTIA) continuing despite heparin (n = 14); group D, CTIA (above criteria) ceasing with heparin (n = 21); and group E, anatomically compelling situation on carotid angiography (n = 13). Data collected included preoperative and postoperative Neurologic Event Severity Score (NESS), CHAT classification, arteriosclerosis risk factors, demographics, and long-term overall and transient ischemic attack/stroke-free survival rates.

RESULTS

Risk factors and demographics were similar in all groups. By NESS criteria the conditions of 97.3% of patients in the neurologically unstable groups A to C were improved or stabilized after operation, with one deterioration (2.7%). All patients in group B either stabilized or improved. In group D, one patient's NESS deteriorated, resulting in 3.5% overall morbidity rate and no deaths for groups A to D. Follow-up showed an overall survival rate by Kaplan-Meier analysis equivalent to a matched control population, with 85% alive at 5 years. The cumulative TIA/stroke-free survival rate at 5 years was 75%.

CONCLUSIONS

In this retrospective series, CEA performed for compelling or unstable neurologic findings carried low morbidity and mortality rates. Early aggressive surgical therapy of neurologically unstable patients may be warranted because our results improved on the anticipated natural history of the conditions studied. Further clarification of proper patient selection is necessary before this principle can be applied broadly.