The acetazolamide challenge: imaging techniques designed to evaluate cerebral blood flow reserve

Cerebral blood flow was analyzed by the stable xenon (Xe)/CT scanning technique in 29 patients with significant vascular lesions before and after administration of an acetazolamide (Diamox) vasodilatory challenge. Three response types were identified: I, normal flow before Diamox with flow augmentation after Diamox; II, low flow before Diamox with flow augmentation after Diamox; and III, low or normal flow before Diamox with no augmentation or decreased flow after Diamox. Twenty-four percent of the patients studied qualified for category III. We believe that patients in this category represent a group of individuals without blood flow reserve whose clinical management should include careful consideration of their hemodynamic status. The Xe/CT scanning technique with the addition of Diamox flow challenge is a clinically accessible and effective method for assessing cerebral blood flow and blood flow reserve.     

Aqueduct stenosis due to venous ectasia with a dural arteriovenous fistula

We report aqueduct compression by venous ectasia in a 65-year-old man with a dural arterio-venous fistula in the posterior cranial fossa draining into a superior vermian vein. Conventional and phase-contrast MRI showed the aqueduct stenosis and the causative dilated vein. Received: 9 November 1998 Accepted: 2 August 1999     

Cervical myelopathy associated with intracranial dural arteriovenous fistula: MR findings before and after treatment.

The MR findings in three patients with intracranial dural arteriovenous fistula associated with cervical myelopathy are described. The MR appearance of an enlarged cord with associated abnormal signal and enhancement is nonspecific and can simulate tumor, demyelination, and inflammation. Enlarged perimedullary vessels may not always be identifiable, but if present, should suggest the presence of an arteriovenous fistula.     

Impaired cerebral vasoreactivity after embolization of arteriovenous malformations: assessment with serial acetazolamide challenge xenon CT

Embolization of a portion of the nidus of an arteriovenous malformation not only may alter hemodynamics within the nidus, but also may change blood flow dynamics in adjacent normal vessels. Sequential acetazolamide-challenge xenon CT cerebral blood flow studies were performed in eight patients before and after embolization of arteriovenous malformations to assess the hemodynamic effects on the major vascular territories supplying the malformation. Acetazolamide is a potent cerebral vasodilator, and its administration combined with cerebral blood flow studies allows assessment of cerebral vasoreactivity. In seven of the eight patients, one or more parenchymal areas exhibited a normal cerebral blood flow augmentation response to acetazolamide before embolization, but diminished acetazolamide flow augmentation was seen after embolization, indicating abnormal vasoreactivity. We found that the decrease in vasoreactivity peaked 6-10 days after embolization. In one of the eight patients, a temporary delayed neurologic deficit developed during a period of impaired cerebral vasoreactivity following embolization. Our results suggest that embolization of an arteriovenous malformation can induce vasoreactivity changes in adjacent normal vessels. Because these changes appear to be somewhat time-dependent, an appropriate interval should be observed between embolization stages or before surgical resection of an arteriovenous malformation following embolization to allow hemodynamic equilibration to occur. Acetazolamide challenge combined with serial cerebral blood flow studies following embolization enables determination of this hemodynamic equilibration.     

Noninvasive magnetic resonance imaging evaluation of cerebral blood flow with acetazolamide challenge in patients with cerebrovascular stenosis.

To evaluate the utility of using magnetic resonance imaging (MRI) of cerebral blood flow (CBF) in conjunction with pharmacologic flow augmentation, the authors imaged 14 patients with ischemic symptoms referable to large artery cerebrovascular stenosis of the anterior circulation. CBF was measured by using continuous arterial spin labeling (CASL) both at rest and 10 minutes after 1 g intravenous acetazolamide on a commercial 1.5 Tesla scanner. Quantitative CBF images were calculated along with augmentation images showing the effects of acetazolamide. Interpretable studies were obtained from all patients. Based on the image data as well as a region of interest analysis of CBF changes in middle cerebral artery distributions, varying patterns of augmentation were observed that suggested differing mechanisms of ischemic symptomatology. The ability to obtain this information in conjunction with a structural MRI examination extends the diagnostic potential for MRI in cerebrovascular disease and allows the value of augmentation testing in clinical management to be assessed more widely. J. Magn. Reson. Imaging 1999;10:870-875.     

Subcortical calcification on CT in dural arteriovenous fistula with cortical venous reflux

We report 3 cases of dural arteriovenous fistula (dAVF) with cortical venous reflux (CVR) presenting calcification in the cortico-medullary junction at the bottom of cerebral sulci on unenhanced CT. This likely results from chronic venous congestion with resulting impaired perfusion of the involved parenchyma. dAVF with CVR, which is known to have poor prognosis without treatment, should be included in the differential diagnosis of subcortical calcification on CT.     

Flow-sensitive alternating inversion recovery (fair) imaging for retrograde cortical venous drainage related to intracranial dural arteriovenous fistula

Introduction  

To evaluate the hypothesis that flow-sensitive alternating inversion recovery (FAIR) magnetic resonance (MR) imaging can detect retrograde cortical venous drainage (RCVD) in patients with intracranial dural arteriovenous fistula (DAVF).     

MR imaging findings of intracranial dural arteriovenous fistulas: relations with venous drainage patterns

BACKGROUND AND PURPOSE: Venous drainage patterns are a major determinant of clinical outcome in intracranial dural arteriovenous fistula (DAVF) patients. In this study, we sought to identify MR imaging finding differences between DAVF types classified on the basis of venous drainage patterns. METHODS: Twenty-seven patients diagnosed as having DAVFs by conventional angiography were included. Medical records (n = 27), and MR imaging (n = 27) and MR angiography (MRA; n = 11) findings were retrospectively reviewed. MR imaging findings included flow void cluster, engorged ophthalmic vein/proptosis, white matter hyperintensity, intracranial hemorrhage, dilated leptomeningeal or medullary vessels, venous pouch, and leptomeningeal or medullary vascular enhancements. MRA findings included identifiable fistula, venous flow-related enhancement, and prominent extracranial vessels. Patients' presentations and MR imaging findings were compared among angiographic type I, II, and III cases (according to Borden's classification), and MRA findings were compared between cases with and without retrograde leptomeningeal venous drainage (RLVD). RESULTS: Patient presentations were aggressive in one (13%) of the type I cases, 5 (50%) of the type II cases, and 8 (100%) of the type III cases (P = .002). Aggressive presentations included hemorrhage, focal neurologic deficits, seizures, intracranial hypertension, and an altered mental status. MR images showed significantly higher frequencies of dilated leptomeningeal or medullary vessels in a higher type [0 in type I, 5 (42%) in type II, and 7 (100%) in type III], and of leptomeningeal or medullary vascular enhancements [0 in type I, 4 (33%) in type II, and 7 (100%) in type III]. By using MRA, fistulas were identified only in cases with RLVD (5 [83%]). Venous flow-related enhancement was present in 10 cases (91%). A sole false-negative case on MRA, as compared with conventional angiography, resulted from nonvisualization of the slow venous flow (8%). No false-positive fistula was found at the other intracranial sites in all cases. Overall, MRA assessment for DAVF was adequate for both fistula and venous flow-related enhancement in 10 cases (91%) and inadequate in a remaining case because of the fistular location out of field. CONCLUSION: MR imaging demonstration of leptomeningeal or medullary vascular dilation and enhancements may be associated with features that are considered predictors of a poor outcome and indicates a need for urgent therapy in intracranial dural AVF patients. MRA is a complementary tool for the identification of dural AVF with venous flow-related enhancement.     

A comparative study of simple methods to quantify cerebral blood flow with acetazolamide challenge by using iodine-123-IMP SPECT with one-point arterial sampling

The aim of this study was to compare the accuracy of simplified methods for quantifying rCBF with acetazolamide challenge by using 123I-N-isopropyl-p-iodoamphetamine (IMP) and SPECT with one-point arterial sampling. After acetazolamide administration we quantified rCBF in 12 subjects by the following three methods: (a) the modified microsphere method, (b) the IMP-autoradiographic (ARG) method based on a two-compartment one-parameter model, and (c) the simplified method based on a two-compartment two-parameter model (functional IMP method). The accuracy of these methods was validated by comparing rCBF values with those obtained by the standard method: the super-early microsphere method with continuous withdrawal of arterial blood. On analyzing rCBF in each flow range (0-0.25, 0.25-0.5, 0.5-0.75 and more than 0.75 ml/g/min), rCBF values obtained by both methods (a) and (c) showed significant correlations (p < 0.01) with those obtained by the standard method in every range, but rCBF values obtained by method (b) did not significantly correlated in the high flow range (0.5-0.75 and more than 0.75 ml/g/min). Method (c) was found to be the most accurate, even though it needs two serial SPECT scans. When requiring one SPECT scan, method (a) was considered to be superior to method (b) because of its accuracy, especially in high flow regions loaded with acetazolamide.     

Enhanced cervical MRI in identifying intracranial dural arteriovenous fistulae with spinal perimedullary venous drainage

Diagnosis of an intracranial dural arteriovenous fistula (DAVF) with spinal perimedullary venous drainage is challenging because the presenting symptoms are usually related to dysfunction of the spine, not of the brain. Repeated spinal angiograms are usually performed before the diagnosis is finally made by cerebral angiography. We report two cases of intracranial DAVFs with spinal perimedullary venous drainage. In both cases contrast-enhanced cervical MRI demonstrated dilated lower brainstem and upper spinal veins, which, we believe, is a good indicator of the existence of such drainage. We suggest that, in cases with perimedullary serpentine enhancement on thoracic or lumbar MR images, additional Gd-enhanced cervical spinal MR imaging should be performed. The simple process of tracing the veins upwards may avoid a lot of unnecessary examinations and delay in the diagnosis. Received: 3 July 1997 Accepted: 6 August 1997     

Regional cerebral blood flow response to oral amphetamine challenge in healthy volunteers.

Functional brain imaging is a powerful tool for examining the central nervous system (CNS) response to pharmacologic challenges. Amphetamine is of interest both because of its role as a stimulant of the dopaminergic system and because of its use to alter mood in mood-disordered patients, particularly in patients suffering from depression. In this study, we report the effects of oral D-amphetamine relative to placebo on regional cerebral blood flow (rCBF) measured by SPECT in healthy volunteers to characterize the normal CNS response to this primarily dopaminergic stimulant. METHODS: SPECT was used to assess changes in rCBF induced by amphetamine in 16 healthy volunteers. Subjects received placebo and then 0.4 mg/kg oral amphetamine in a fixed-order single-blind design and were imaged on a triple-head tomograph. Another six healthy volunteers received placebo at both times to assess normal rCBF variability. rCBF changes were assessed with a three-dimensional voxel-based analysis integrated into an automated coregistration system. Data were automatically normalized to whole-brain counts and coregistered. Resultant rCBF changes were evaluated parametrically through the formation of an image whose voxel values were based on the paired t statistic. RESULTS: Amphetamine increased rCBF in two mesial prefrontal zones (Brodmann's areas 8 and 10), inferior orbital frontal lobe (area 11), brain stem (ventral tegmentum), anteromesial temporal lobe (amygdala), and anterior thalamus. Amphetamine decreased rCBF to motor cortex, visual cortex, fusiform gyrus, posterolateral temporal lobe, and right lateral temporal lobe. CONCLUSION: Our data suggest that amphetamine induces focal increases and decreases in rCBF in healthy volunteers in areas primarily innervated by dopamine pathways and in areas with secondary (primarily limbic) affiliations. These data are consistent with glucose metabolic data from autoradiographic studies in animals, in which the largest increases are seen in brain stem, followed by striatum, thalamus, and frontal and sensory cortices. Frontopolar and temporal increases observed in our study appear to be unique to humans.     

静脉窦开通治疗硬脑膜动静脉瘘伴静脉窦闭塞3例

目的 探讨静脉窦开通治疗硬脑膜动静脉瘘(DAVF)伴静脉窦闭塞的效果.方法 回顾性分析2009年9月至2015年5月收治的3例DAVF伴静脉窦闭塞患者临床资料.结果 1例患者经单纯开通静脉窦后治愈DAVF,2例患者经机械性开通联合球囊扩张恢复静脉窦主干通畅后症状明显好转;均未出现介入治疗并发症.结论 部分DAVF伴静脉窦闭塞患者静脉窦开通后正常脑静脉回流通畅,横窦、乙状窦周围DAVF瘘口能达到彻底、永久闭合.静脉窦开通恢复有效血流动力学是治疗DAVF伴静脉窦闭塞的有效方法.     

Intraosseous venous structures adjacent to the jugular tubercle associated with an anterior condylar dural arteriovenous fistula

Purpose

Although involvement of the osseous component with an anterior condylar dural arteriovenous fistula (AC-DAVF) has been frequently described, osseous venous structures in which AC-DAVFs develop have not been fully elucidated. We investigated osseous venous structures adjacent to the hypoglossal canal in normal controls and patients with AC-DAVFs.

Methods

The study included 50 individuals with unruptured aneurysms as normal controls and seven patients with AC-DAVFs. Osseous venous structures adjacent to the hypoglossal canal in normal controls were analyzed using computed tomography (CT) digital subtraction venography. In patients with AC-DAVFs, the fistulous pouches, draining veins, and surrounding venous structures were examined using cone beam CT.

Results

In 46.0% of laterals in normal controls, osseous venous structures were visualized within the jugular tubercle superomedially to the hypoglossal canal. We named these structures the jugular tubercle venous complex (JTVC). The JTVC was always continuous with the anterior condylar vein and was sometimes connected to surrounding venous channels. We detected nine fistulous pouches in the seven patients with AC-DAVFs. The fistulous pouches were in the JTVC (33.3%), anterior condylar vein (33.3%), and other venous channels within the exoccipital region (33.3%).

Conclusion

Although the JTVC is a venous structure frequently found in normal people, it had not been investigated until now. The venous channel between the anterior condylar vein and JTVC is a common origin site for AC-DAVFs, and it was associated with 66.6% of the AC-DAVF cases in the current study.