Detection of misery perfusion in the cerebral hemisphere with chronic unilateral major cerebral artery steno-occlusive disease using crossed cerebellar hypoperfusion: comparison of brain SPECT and PET imaging

Purpose

In patients with unilateral internal carotid or middle cerebral artery (ICA or MCA) occlusive disease, the degree of crossed cerebellar hypoperfusion that is evident within a few months after the onset of stroke may reflect cerebral metabolic rate of oxygen in the affected cerebral hemisphere relative to that in the contralateral cerebral hemisphere. The aim of the present study was to determine whether the ratio of blood flow asymmetry in the cerebellar hemisphere to blood flow asymmetry in the cerebral hemisphere on positron emission tomography (PET) and single photon emission computed tomography (SPECT) correlates with oxygen extraction fraction (OEF) asymmetry in the cerebral hemisphere on PET in patients with chronic unilateral ICA or MCA occlusive disease and whether this blood flow ratio on SPECT detects misery perfusion in the affected cerebral hemisphere in such patients.

Methods

Brain blood flow and OEF were assessed using ¹⁵O-PET and N-isopropyl-p-[¹²³I]iodoamphetamine (¹²³I-IMP) SPECT, respectively. All images were anatomically standardized using SPM2. A region of interest (ROI) was automatically placed in the bilateral MCA territories and in the bilateral cerebellar hemispheres using a three-dimensional stereotaxic ROI template, and affected-to-contralateral asymmetry in the MCA territory or contralateral-to-affected asymmetry in the cerebellar hemisphere was calculated. Sixty-three patients with reduced blood flow in the affected cerebral hemisphere on ¹²³I-IMP SPECT were enrolled in this study.

Results

A significant correlation was observed between MCA ROI asymmetry of PET OEF and the ratio of cerebellar hemisphere asymmetry of blood flow to MCA ROI asymmetry of blood flow on PET (r?=?0.381, p?=?0.0019) or SPECT (r?=?0.459, p?=?0.0001). The correlation coefficient was higher when reanalyzed in a subgroup of 43 patients undergoing a PET study within 3 months after the last ischemic event (r?=?0.541, p?=?0.0001 for PET; r?=?0.609, p?<?0.0001 for SPECT). The blood flow ratio on brain perfusion SPECT in all patients provided 100 % sensitivity and 58 % specificity, with 43 % positive and 100 % negative predictive values for detecting abnormally elevated MCA ROI asymmetry of PET OEF.

Conclusion

The ratio of blood flow asymmetry in the cerebellar hemisphere to blood flow asymmetry in the cerebral hemisphere on PET and SPECT correlates with PET OEF asymmetry in the cerebral hemisphere, and this blood flow ratio on SPECT detects misery perfusion in the affected cerebral hemisphere.     

Crossed "cerebral" diaschisis? Seven cases with unilateral cerebellar vascular lesion which showed decreased perfusion in the contralateral cerebral cortex

In 7 cases with unilateral cerebellar vascular lesion, decreased perfusion was observed in the contralateral cerebral cortex by single photon emission computed tomography (SPECT) with I-123 labeled N-isopropyl-p-iodoamphetamine (IMP). These cases had symptoms due to cerebellar lesions but did not show any cerebral cortical symptoms. Reduction of cerebral cortical perfusion appeared on more than 25 days after the onset of CVA, did not correlate with morphological changes by cranial X-ray computed tomography and digital subtraction angiography in acute phase, and was persistent or irreversible later. We made a guess this phenomenon was due to the remote neuronal effect through cerebellothalamic projection.     

Qualitative versus quantitative assessment of cerebrovascular reactivity to acetazolamide using iodine-123-N-isopropyl-p-iodoamphetamine SPECT in patients with unilateral major cerebral artery occlusive disease

BACKGROUND AND PURPOSE: Qualitative measurement of regional cerebrovascular reactivity (rCVR) to acetazolamide with single-photon emission CT (SPECT) has been widely used to determine the severity of hemodynamic impairment. We attempted to validate the accuracy of qualitative assessment by using SPECT to detect reduced rCVR compared with rCVR determined quantitatively in patients with unilateral major cerebral artery occlusion. METHODS: Regional cerebral blood flow was assessed with iodine-123-N-isopropyl-p-iodoamphetamine ((123)I-IMP) at rest and after acetazolamide activation in 133 patients with previously symptomatic, unilateral internal carotid or middle cerebral artery occlusion. Quantitative values were calculated by using the (123)I-IMP autoradiographic method and analyzed for each cerebral hemisphere as the percentage change in rCBF between resting and activation studies (%(Hem)). Qualitative rCVR was determined for the target hemisphere distal to the occlusion as the cerebral-interhemispheric asymmetry index (AI(Hem)) and as an index of flow difference between the target cerebral and ipsilateral cerebellar hemispheres (FI(Hem-Cbl)). Values 2 SDs below the mean in healthy volunteers were defined as decreased. RESULTS: Fair agreement was observed between %(Hem) and both AI(Hem) change (resting vs activation, kappa = 0.409) and FI(Hem-Cbl) change (resting vs activation, kappa = 0.440). When %(Hem) was assumed to represent the true determinant of assessing rCVR, AI(Hem) change and FI(Hem-Cbl) change demonstrated sensitivities of 68% and 78%; specificities, 72% and 76%; positive predictive values, 48% and 56%; false-positive incidences, 28% and 24%; and false-negative incidences, 32% and 22% for detecting patients with reduced rCVR, respectively. CONCLUSION: Subgroups of patients with hemodynamic impairment cannot be accurately defined by using rCVR qualitatively measured with SPECT.     

Highly diffusion-sensitized tensor imaging of unilateral cerebral arterial occlusive disease

BACKGROUND AND PURPOSE: Selective neuronal death is a well-recognized histopathologic sequel to moderate ischemic brain damage. However, radiologic visualization of these changes has not been established, even with diffusion tensor imaging (DTI). We sought to determine whether DTI with b values > or =1900 s/mm(2) reveals occult diffusion abnormalities in patients with cerebral arterial occlusive disease. METHODS: Six patients (five men, one woman; mean age +/- standard deviation, 66 +/- 8 years) with unilateral internal carotid or middle cerebral arterial occlusive disease but not parenchymal T2 hyperintensity underwent 3T fast DTI with b < or = 1300 s/mm(2) and slow DTI with b > or = 1900 s/mm(2). We postprocessed mean diffusibility and fractional anisotropy (FA) images from the fast and slow DTI datasets. Standardized asymmetry indices (AIs) were used to identify regional asymmetries. Diagnostic accuracy among the DTI modalities was assessed by means of receiver operating characteristic analysis. RESULTS: In hemispheres ipsilateral to occluded vessel, AIs were significantly elevated on fast mean-diffusibility images of white matter at the levels of the internal capsule (95% confidence interval [CI]: 1.00, 1.09; P = .045) and corona radiata (95% CI: 1.01, 1.12; P = .034). AIs were significantly decreased on slow FA images at the internal capsule (95% CI: 0.84, 0.98; P = .018) and white matter at the internal capsule level (95% CI: 0.92, 1.00, P = .043). The slow FA map had the highest accuracy (89.8%) for detecting the hemisphere ipsilateral to arterial occlusion. CONCLUSION: Slow FA maps acquired by using DTI with high b values are useful for visualizing ischemic brain damage in apparently normal WM.     

高扩散梯度因子值扩散张量成像在评价单侧大脑中动脉闭塞供血区及远隔部位脑白质中的应用价值

目的 采用高b值DTI研究常规MRI上无异常的单侧大脑中动脉闭塞供血区及远隔部位脑白质的影像特征.方法 选取34例常规MRI无异常信号的单侧大脑中动脉闭塞患者,行高b值(2200 s/mm2) DTI成像.所得图像进行后处理,镜像对称法选取双侧放射冠区侧脑室体部层面、内囊前肢、内囊后肢、大脑脚、脑桥中部层面为R0I,测量患者以上部位患、健侧的各向异性分数(FA)值、ADC值及本征值(λ1、λ2、λ3),采用配对t检验比较患者患侧与健侧各测量值.结果 34例患者中,大脑中动脉M1段闭塞左侧16例、右18例.放射冠区健侧FA值、ADC值及λ1、λ2、λ3值分别为0.443±0.033,(5.804±0.282)×10-3、( 5.651±0.350)×10-3、(6.099±0.353)×10-3、(6.372±0.355)×10-3 m2/s,患侧各值分别为0.419±0.032,(5.975±0.272)×10-3、(5.704±0.365)× 10-3、(6.412±0.368)× 10-3、(6.605±0.343)×10-3 mm2/s,患侧FA值较健侧减小(t=11.614,P＜0.01),ADC、λ1、λ2及λ3值较健侧增大(t值分别12.421、7.447、10.244、9.890,P值均＜0.01).患侧内囊前肢及后肢FA值分别为0.609 ±0.026、0.674±0.033,λ1值分别为(5.330±0.462) ×101、(5.171±0.456)×10-3 mm2/s,健侧对应部位FA值和λ,值分别为0.622±0.026、0.694±0.034,(5.064±0.448) ×10-3、(4.924±0.365)×10-3 mm2/s,患侧内囊前、后肢FA值较健侧减小(t值分别7.823、8.013,P值均＜0.01),λ1值较健侧增大(t值分别7.811、8.800,P值均＜0.01),ADC、λ2及λ3值两侧比较差异无统计学意义.大脑脚、脑桥的各测量值在两侧间比较差异均无统计学意义.结论 高b值DTI可敏感评价MRI无异常信号的闭塞脑动脉供血区的脑白质损害,其远隔部位脑白质未见损害.     

Clinical implication and prognosis of normal baseline cerebral blood flow with impaired vascular reserve in patients with major cerebral artery occlusive disease

Objective  

To investigate the prognosis of patients with cerebrovascular steno-occlusive disease who have preserved baseline cerebral blood flow (CBF) and reduced cerebral vasoreactivity (CVR), they were followed up after scans of positron emission tomography (PET).     

Crossed cerebellar diaschisis in herpes simplex encephalitis

Diaschisis is extremely rare in patients with viral encephalitis. We report the phenomenon of crossed cerebellar diaschisis (CCD) in a 73-year-old man with acute herpes simplex type-1 (HSV-1) encephalitis. The diagnosis of HSV-1 encephalitis was confirmed by detecting HSV-1 deoxyribonucleic acid in the cerebrospinal fluid (CSF). Magnetic resonance images (MRI) showed enhancing lesions at bilateral temporal lobes, insular cortices, and right frontoparietal lobes. Increase signal intensity on T2-weighted images was seen in the mesecephalon. Technetium-99m ethyl cysteinate dimer (99mTc-ECD) single photon emission computed tomography (SPECT) of the brain showed a large area of hypoperfusion in the right frontotemporoparietal lobes. The side-to-side cerebellar count revealed 19% reduction of the radioisotope tracer uptake in the left cerebellum. The phenomenon of CCD was proposed to be due to both anterograde disconnection of the corticopontocerebellar tracts and retrograde deafferentation of dentatothalamocortical projections.     

Spontaneous improvement in reduced vasodilatory capacity in major cerebral arterial occlusive disease

Reduced vasodilatory capacity resulting from occlusive lesions of the major cerebral arteries may return to normal without surgical revascularisation. We aimed to determine prospectively the frequency and predictors of recovery of impaired haemodynamics as demonstrated by acetazolamide (ACZ) reactivity on single-photon emission computed tomography (SPECT). Vasoreactivity was measured by ¹²³I-IMP SPECT with an ACZ challenge, in 37 medically treated patients with unilateral occlusive disease of the internal carotid or middle cerebral artery at an interval of 1–2 years. Each ACZ challenge test was analysed semiquantitatively by calculating the degree of increase in cerebral blood flow (CBF) asymmetry after ACZ administration (ΔAI). Vasodilatory capacity was abnormal initially in 20 patients (65 %); eight of whom (40 %) exhibited spontaneous normalisation on follow-up. Although the baseline characteristics did not differ significantly between patients with or without increase in reactivity, logistic regression analysis revealed that the initial ΔAI (P < 0.05) and the type of vascular lesion (stenosis or occlusion) (P < 0.05) correlated significantly with a return towards normal of reduced ACZ reactivity. Spontaneous improvement of impaired vasodilatory capacity may not be a rare phenomenon. We found that mild reduction in the initial ACZ reactivity and a stenosis, but not complete occlusion, were independent factors contributing to normalisation of impaired cerebral haemodynamics. Received: 12 October 1998/Accepted: 27 April 1999     

Crossed cerebellar diaschisis in chronic Broca's aphasia

The cerebellum has anatomical connections to the cerebral cortex, through which it can affect language function. To study these connections, we investigated patients with chronic Broca's aphasia using MRI and single-photon emission computed tomography (SPECT). We selected 15 such patients (9 male, 6 female, aged 17–64 years, mean age 56 years) from 30 chronically aphasic patients. Using the results of SPECT, we divided them into patients with (group 1) and without (group 2) crossed cerebellar diaschisis (CCD). We compared the language function of the two groups. Patients in group 1 showed classical Broca's aphasia, while patients in group 2 showed mainly word-finding difficulty. Patients with CCD hat infarcts involving the lower part of the frontal gyrus but patients without CCD did not, which suggests that this region may have functional and anatomical connections with the cerebellum. Our findings support the notion that the cerebellum contributes to language. Received: 3 July 1996 Accepted: 7 November 1996     

Crossed cerebellar diaschisis and loss of consciousness during temporary balloon occlusion of the internal carotid artery.

We encountered a case of crossed cerebellar diaschisis during temporary balloon occlusion of the internal carotid artery in a 59-year-old woman. The rapidity of the diaschisis was unusual and SPECT scanning was adequate to show the early defect.     

Significance of increased oxygen extraction fraction in five-year prognosis of major cerebral arterial occlusive diseases.

In major cerebral arterial occlusive diseases, patients with increased oxygen extraction fraction (OEF), which is measured with PET, may be at increased risk for cerebral ischemia. However, the clinical significance of increased OEF remains unclear. This study investigated whether increased OEF is an independent predictor of 5-y risk of subsequent stroke. METHODS: We prospectively evaluated the relationship between the regional hemodynamic status of cerebral circulation and the subsequent risk of stroke in 40 patients with symptomatic internal carotid or middle cerebral arterial occlusive diseases who underwent PET. Patients were divided into two hemodynamic categories according to the mean hemispheric value of OEF-in the hemisphere supplied by the artery with symptomatic disease: one group with increased OEF and one with normal OEF. All patients were followed for 5 y with medical treatment until the recurrence of stroke or death. RESULTS: During 5 y, 11 total and 9 ipsilateral ischemic strokes occurred. The incidences of all ischemic strokes in patients with increased OEF and in those with normal OEF were 5 of 7 and 6 of 33 patients, respectively. There were 4 ipsilateral ischemic strokes in patients with increased OEF and 5 in those with normal OEF. Kaplan-Meier analysis revealed that the risks of all stroke and ipsilateral ischemic stroke in patients with increased OEF were significantly higher than in those with normal OEF (log-rank test; P<0.0002 and P<0.0018, respectively). Multivariate analysis with the Cox proportional hazards model showed that increased OEF significantly increased stroke recurrence: the relative risk was 7.2 (95% confidence interval [CI], 2.0-25.5; P<0.005) for all stroke and 6.4 (95% CI, 1.6-26.1; P<0.01) for ipsilateral stroke. An increase in the absolute OEF value was a better predictor of recurrent ischemic stroke than was OEF asymmetry. CONCLUSION: These findings suggest that an increased OEF is an independent predictor of 5-y risk of subsequent stroke. Identification of patients with increased OEF may have clinical significance in preventing recurrent stroke.     

Significance of postoperative crossed cerebellar hypoperfusion in patients with cerebral hyperperfusion following carotid endarterectomy: SPECT study

Purpose Cerebral hyperperfusion after carotid endarterectomy (CEA) results in cerebral hyperperfusion syndrome and cognitive impairment. The goal of the present study was to clarify the clinical significance of postoperative crossed cerebellar hypoperfusion (CCH) in patients with cerebral hyperperfusion after CEA by assessing brain perfusion with single-photon emission computed tomography (SPECT). Methods Brain perfusion was quantitatively measured using SPECT and the [¹²³I]N-isopropyl-p-iodoamphetamine-autoradiography method before and immediately after CEA and on the third postoperative day in 80 patients with ipsilateral internal carotid artery stenosis (≥70%). Postoperative CCH was determined by differences between asymmetry of perfusion in bilateral cerebellar hemispheres before and after CEA. Neuropsychological testing was also performed preoperatively and at the first postoperative month. Results Eleven patients developed cerebral hyperperfusion (cerebral blood flow increase of ≥100% compared with preoperative values) on SPECT imaging performed immediately after CEA. In seven of these patients, CCH was observed on the third postoperative day. All three patients with hyperperfusion syndrome exhibited cerebral hyperperfusion and CCH on the third postoperative day and developed postoperative cognitive impairment. Of the eight patients with asymptomatic hyperperfusion, four exhibited CCH despite resolution of cerebral hyperperfusion on the third postoperative day, and three of these patients experienced postoperative cognitive impairment. In contrast, four patients without postoperative CCH did not experience postoperative cognitive impairment. Conclusions The presence of postoperative CCH with concomitant cerebral hyperperfusion reflects the development of hyperperfusion syndrome. Further, the presence of postoperative CCH in patients with cerebral hyperperfusion following CEA suggests development of postoperative cognitive impairment, even when asymptomatic.     

Resting and hypercapnic rCBF in patients with unilateral occlusive disease of the internal carotid artery

Regional cerebral blood flow was measured by the 133Xe inhalation technique in 15 patients with severe unilateral internal carotid artery stenosis (75%) or occlusion, and in the absence of evidence of any sign of occlusive disease in other main afferent cerebral arteries. A comparison with normal subjects showed that lowered resting flow in both hemispheres was a common finding in all patients. Interhemispheric asymmetry was present only in patients with occlusion and the precentral, posterior temporal, and occipital regions were the most seriously affected. The CO2 reactivity was substantially reduced in both hemispheres of all stenotic and occluded patients, but occluded patients showed an increased reduction of CO2 reactivity only in the ipsilateral hemisphere. In addition to an hypothetical age effect, the atherosclerotic involvement of the cerebral vascular system leads to a reduction of flow and loss of CO2 reactivity in both hemispheres. In this context, the collateral supply capacity is not overloaded in case of a unilateral severe stenosis but fails in case of a unilateral occlusion of the internal carotid artery. A suitable estimate of the blood flow reduction as a result of occlusion is made by the hemispheric and regional laterality indices applied in resting and hypercapnia conditions. These indices could be used as indicators for endarterectomy or bypass surgery as well as a sensitive means for appreciating cerebral blood flow response to treatment.     

Evaluation of crossed cerebellar diaschisis in 30 patients with major cerebral artery occlusion by means of quantitative I-123 IMP SPECT

Quantitative crossed cerebellar diaschisis (CCD) and the correlation with a reduction in supratentorial regional cerebral blood flow (rCBF) and cerebrovascular reserve capacity (CVR) were investigated in clinically stable patients with major cerebral artery occlusion by the iodine-123-N-isopropyl-p-iodoamphetamine (I-123 IMP) single photon emission computed tomography (SPECT) method. Thirty patients with major cerebral artery occlusion underwent SPECT by the I-123 IMP autoradiographic method. Regional CBF was measured in the cerebral hemisphere, frontal and parietal lobes, temporo-parietal lobe, and cerebellum both at rest and after administration of acetazolamide. Eighteen of 30 patients (60%) had CCD. CCD was significantly related to magnetic resonance imaging evidence of infarction. Quantitative CCD was 17% and the CVR in the cerebellum was preserved in patients with CCD. There was a significant difference in CBF and CVR between the affected and normal sides in all regions of interest in the patients without CCD [CBF (ml/100 g/min): hemisphere (H), normal side (N): 31.4 +/- 6.8, affected side (A): 27.5 +/- 7.4; p < 0.05. CVR: H, N: 0.56 +/- 0.38, A: 0.42 +/- 0.18; p < 0.01]. CCD is common in patients with major cerebral artery occlusion, and quantitative I-123 IMP SPECT is helpful in detecting CCD in clinically stable patients with occlusion of major cerebral arteries.     

Cerebrovascular occlusive complications in osteopetrosis major

Summary We report the case of a 16-year-old patient with osteopetrosis major, complaining of transient sensory and motor disturbances in the left upper limb and diziness on changing the position of his head. Selective angiography of the cerebral vessels showed severe narrowing of the internal carotid artery within the petrous carotid canal and in its supraclinoid portion. The cervical vertebral arteries showed multiple stenosis within the vertebral canal. These findings are explained by narrowing of the basal foramina by the osteopetrotic bone.