D.R. Rutgers

A Longitudinal Study of Collateral Flow Patterns in the Circle of Willis and the Ophthalmic Artery in Patients With a Symptomatic Internal Carotid Artery Occlusion

BACKGROUND AND PURPOSEnThe purpose of the present study was to assess whether the direction of flow via the circle of Willis and the ophthalmic artery (OphA) changed over time in patients with a symptomatic occlusion of the internal carotid artery (ICA) who did not experience recurrent cerebral ischemic symptoms.nnnMETHODSnSixty-two patients with a symptomatic ICA occlusion were investigated within 6 months after symptoms occurred. The investigations were repeated after 6 and 12 months. The directions of flow in the A1 segment and the posterior communicating artery (PCoA), both on the side of the symptomatic ICA occlusion, were assessed with the use of magnetic resonance angiography. The pattern of collateral flow via the circle of Willis was categorized as via the A1 segment only, via the PCoA only, via the A1 segment plus the PCoA, or no collateral flow via the circle of Willis. The direction of flow in the OphA was investigated with transcranial Doppler sonography. CO(2) reactivity was determined with transcranial Doppler sonography to investigate whether changes in flow patterns were accompanied by changes in cerebrovascular reactivity.nnnRESULTSnThere were no statistically significant changes over time in the direction of blood flow in the A1 segment and the PCoA or in the pattern of collateral flow via the circle of Willis. On average, 72% of patients with a unilateral ICA occlusion (n=41) had willisian collateral flow compared with 37% of patients with a bilateral ICA occlusion (n=21; P<0.05). Patients with a unilateral ICA occlusion tended to a lower prevalence of reversed flow via the OphA over time. CO(2) reactivity did not change significantly in any patient group. In patients with a unilateral ICA occlusion, decreased CO(2) reactivity was associated with a higher prevalence of absent willisian collateral flow and a lower prevalence of collateral flow via the A1 segment plus the PCoA.nnnCONCLUSIONSnThe absence of recurrent cerebral ischemic symptoms in patients with a symptomatic ICA occlusion is not associated with an improvement in collateral flow via the circle of Willis or the OphA during 1.5-year follow-up.

Preoperative MRA Flow Quantification in CEA Patients Flow Differences Between Patients Who Develop Cerebral Ischemia and Patients Who Do Not Develop Cerebral Ischemia During Cross-Clamping of the Carotid Artery

Background and Purpose We sought to investigate whether preoperative volume flow in the internal carotid arteries (ICAs), the basilar artery (BA), and the middle cerebral arteries (MCAs) and collateral flow via the circle of Willis differ between patients who do and patients who do not develop cerebral ischemia during clamping of the carotid artery in carotid endarterectomy (CEA). Methods Quantitative volume flow in the ICAs, BA, and MCAs and directional flow in the circle of Willis were measured preoperatively with 2-dimensional phase-contrast MR angiography in 86 CEA patients. During the operation, electroencephalographic (EEG) recordings were obtained that were monitored by a clinical neurophysiologist. Reference volume flow values were assessed in 24 control subjects. Results In patients with an ICA stenosis without contralateral ICA occlusion (n=62), of whom 16% developed ischemic EEG changes during clamping, preoperative flow in the clamped ICA was significantly higher in patients with cerebral ischemia than in patients without (mean, 278 versus 160 mL/min;P <0.05). Flow in the contralateral ICA (156 versus 273 mL/min;P <0.01), flow in the BA (116 versus 165 mL/min;P <0.05), and presence of collateral flow via the circle of Willis to the clamped ICA (0% versus 37%;P <0.05) were significantly lower. MCA flow did not differ significantly between groups. Additionally, in patients with an ICA stenosis and a contralateral ICA occlusion (n=24), of whom 42% developed cerebral ischemia, preoperative flow in the clamped ICA was significantly higher in patients with cerebral ischemia than in patients without (309 versus 239 mL/min;P <0.05). BA flow, MCA flow, and presence of willisian collateral flow (0% versus 14%) did not differ significantly between groups. Conclusions Preoperative volume flow in the clamped ICA is significantly higher in CEA patients with ischemic EEG changes during clamping than in CEA patients without such changes. The latter patients probably have better developed collateral pathways preoperatively.

Sustained Bilateral Hemodynamic Benefit of Contralateral Carotid Endarterectomy in Patients With Symptomatic Internal Carotid Artery Occlusion

Background and Purpose— We sought to investigate whether in patients with a symptomatic internal carotid artery (ICA) occlusion, endarterectomy of a severe stenosis of the contralateral carotid artery can establish long-term cerebral hemodynamic improvement. Methods— Nineteen patients were studied on average 1 month before and 6 months after contralateral carotid endarterectomy (CEA). Volume flow in the main extracranial and intracranial arteries was measured with MR angiography. Collateral flow via the circle of Willis and the ophthalmic arteries was studied with MR angiography and transcranial Doppler sonography, respectively. Cerebral metabolism and CO2 vasoreactivity were investigated with MR spectroscopy and transcranial Doppler sonography, respectively. Twelve nonoperated patients with a symptomatic ICA occlusion and contralateral ICA stenosis, who were matched for age and sex, served as control patients. Results— In patients who underwent surgery, flow in the operated ICA increased significantly (P <0.05) and flow in the basilar artery decreased significantly (P <0.01) after CEA. On the occlusion side, mean flow in the middle cerebral artery increased significantly from 71 to 85 mL/min (P <0.05) after CEA. The prevalence of collateral flow via the anterior communicating artery to the occlusion side increased significantly (47% before and 84% after CEA;P <0.05), while the prevalence of reversed ophthalmic artery flow on the operation side decreased significantly (42% before and 5% after CEA;P <0.05). In the hemisphere on the side of the ICA occlusion, lactate was no longer detected after CEA in 80% of operated patients, whereas it was no longer detected over time in 14% of nonoperated patients (P <0.05). CO2 reactivity increased significantly in operated patients in both hemispheres (P <0.01). Conclusions— Contralateral CEA in patients with a symptomatic ICA occlusion induces cerebral hemodynamic improvement not only on the side of surgery but also on the side of the ICA occlusion.

Effect of Carotid Endarterectomy on Primary Collateral Blood Flow in Patients With Severe Carotid Artery Lesions

Background and Purpose— In patients with severe obstruction of the internal carotid artery (ICA), it is recognized that the preoperative failure to visualize collaterals of the circle of Willis increases the risk of hemispheric ischemia before, during, and after carotid endarterectomy (CEA). The purpose of the present study was to assess the effect of CEA on the anatomy and function of the circle of Willis. Methods— Time-of-flight and phase-contrast MR angiography were used to study changes in vessel diameter and collateral flow of the circle of Willis in 48 patients with 70% to 99% ICA stenosis before and after CEA. Results— In patients with unilateral ICA stenosis, all preoperative vessel diameters on both sides of the circle of Willis were larger than in control subjects. All demonstrated a significant diameter decrease to reach normal values after CEA. Furthermore, preoperative collateral flow patterns normalized after CEA (P =0.03). In patients with stenosis and contralateral ICA occlusion, CEA resulted in a significant increase in the prevalence of collateral flow via the anterior communicating artery (33% to 83%, P <0.01) and a significant increase in diameter of both A1 segments (P <0.05) in patients in whom collateral flow developed after CEA. Conclusions— CEA reduces the caliber of compensatory collateral channels to normal levels by MR angiography measurements in the presence of severe unilateral stenosis; when the opposite side is occluded and the stenosis is removed ipsilaterally, a greater amount of compensatory collateral circulation can be measured on both the occluded side and the fully opened side.

Recurrent Stroke in Patients With Symptomatic Carotid Artery Occlusion Is Associated With High-Volume Flow to the Brain and Increased Collateral Circulation

BACKGROUND AND PURPOSEnTo investigate whether the risk of recurrent ipsilateral ischemic stroke in patients with symptomatic carotid artery occlusion (CAO) is related to (1) volume flow in the contralateral internal carotid artery (ICA), basilar artery (BA), and middle cerebral arteries (MCAs), and (2) intracranial collateral flow to the symptomatic side, measured in the first 6 months after the qualifying symptoms occurred.nnnMETHODSnWe prospectively studied 112 patients with symptomatic CAO. Quantitative volume flow was measured with magnetic resonance angiography (MRA) and collateral flow via the circle of Willis with MRA, via the ophthalmic artery (OA) with transcranial Doppler sonography, and via leptomeningeal anastomoses with conventional angiography.nnnRESULTSnDuring 49+/-14 months of follow-up (mean+/-SD), 7 patients had recurrent ipsilateral ischemic stroke. Compared with patients without recurrent stroke, these patients had significantly higher total flow to the brain, ie, ICA+BA flow (mean 536 mL/min versus 410 mL/min; P<0.05), and significantly higher contralateral ICA flow (355 mL/min versus 209 mL/min; P<0.001), whereas BA and MCA flow showed no significant differences. Also, they more often had Willisian collateral flow (P<0.05), mainly caused by increased collateral flow via the posterior communicating artery (PCoA; 71% versus 28%; P<0.05), whereas collateral flow via the OA and leptomeningeal anastomoses did not differ significantly.nnnCONCLUSIONSnRecurrent ipsilateral ischemic stroke in patients with symptomatic CAO is associated with high volume flow to the brain and increased collateral PCoA flow.

Cerebral metabolic changes in patients with a symptomatic occlusion of the internal carotid artery: a longitudinal 1H magnetic resonance spectroscopy study

The objective of this 1H magnetic resonance spectroscopy study was to investigate the time course of the brain metabolites N‐acetyl‐aspartate (NAA), choline, and lactate in patients with transient or minor disabling neurological deficits associated with an occlusion of the internal carotid artery (ICA). Fifty patients had had symptoms of hemispheric ischemia, and 16 had suffered symptoms of retinal ischemia. Single‐voxel proton spectra were obtained from uninfarcted cerebral regions on three occasions: 0–6, 6–12, and 12–18 months after symptoms. values were obtained from 29 control subjects. In the 0–6 month period, patients with hemispheric ischemia showed a significantly lower NAA/creatine ratio in the hemisphere ipsilateral to the ICA occlusion, compared with control subjects and patients with retinal ischemia, and a significantly higher choline/creatine ratio, compared with control subjects. The prevalence of lactate did not differ significantly between patient groups. In the following time periods, the NAA/creatine ratio in patients with hemispheric ischemia tended to return to control values and no longer differed from that in patients with retinal ischemia; the choline/creatine ratio decreased significantly and returned to control values. These results demonstrate that cerebral metabolism is altered in patients with an ICA occlusion who have had a hemispheric ischemic event, but returns (choline) or tends to return (NAA) to control values over time. The metabolic changes occur primarily in the hemisphere ipsilateral to the symptomatic ICA occlusion and are related to the occurrence of the hemispheric ischemic event. J. Magn. Reson. Imaging 2000;11:279–286.

Quantitative cerebral perfusion MRI and CO2 reactivity measurements in patients with symptomatic internal carotid artery occlusion

Quantitative perfusion MRI is a promising new technique capable of offering information on cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). However, it is still unclear how these perfusion parameters relate to the underlying physiological indicators and how they compare to conventional techniques. The purpose of this study was to investigate how quantitative perfusion MRI is related to the cerebrovascular reactivity as measured by transcranial Doppler ultrasonography (TCD) in combination with a CO2 stimulus in patients with a symptomatic occlusion of the internal carotid artery (ICA). Thirty-nine patients with transient or minor disabling retinal or hemispheric ischemic symptoms and an occlusion of the ICA underwent quantitative perfusion MRI and CO2 reactivity measurements by TCD. Perfusion parameters were correlated with cerebrovascular reactivity measurements and compared with measurements of control subjects. The results of this study show a negative correlation between the cerebrovascular reactivity and the time to bolus peak (TBP) both for gray (r = -0.26, P = 0.035) and white matter (r = -0.28, P = 0.026). No correlation between resting CBV, CBF, or MTT and cerebrovascular reactivity was found. Our results indicate that an increase in TBP reflects a poor development of collateral flow, which is supported by a relatively low CO2 reactivity in these patients.

Radiologic-pathologic correlation of the hyperdense middle cerebral artery sign: A case report

To provide a histopathologic substrate of the hyperdense middle cerebral artery (MCA) sign in a patient with MCA infarction. The sign was found to be correlated with accumulation of erythrocytes, fibrin and cellular debris.

A Comparison of Cerebral Hemodynamic Parameters between Transient Monocular Blindness Patients, Transient Ischemic Attack Patients and Control Subjects

Purpose: To assess whether patients with transient monocular blindness (TMB) and patients with hemispheric transient ischemic attacks (hTIA) differ from each other with respect to cerebral hemodynamic parameters. Methods: Seventeen TMB patients and 23 hTIA patients with a moderate to severe stenosis or an occlusion of the internal carotid artery (ICA) underwent magnetic resonance (MR) angiography, 1H MR spectroscopy and transcranial Doppler sonography. Thirty-one control subjects were investigated to obtain reference values for the MR investigations. Quantitative flow was measured in the ICAs, the basilar artery and the middle cerebral arteries (MCA). Metabolic changes in the MCA territory were studied by assessing N-acetyl-aspartate (NAA)/choline ratios and prevalences of lactate. The prevalence of collateral flow was assessed in the circle of Willis and the ophthalmic arteries. The vasomotor reactivity was studied by measuring the CO2 reactivity of the MCA territories. Results: Quantitative flow in the cerebropetal arteries and the MCAs did not differ between TMB patients and hTIA patients. Also patterns of collateral flow, prevalence of lactate and CO2 reactivity were similar. The mean ipsilateral NAA/choline ratio was lower in hTIA patients compared with TMB patients (p < 0.01), and was predominantly correlated with symptomatology (p < 0.01), i.e. whether patients had TMB or hTIA, and not with ipsilateral MCA flow (p = 0.2) or ipsilateral CO2 reactivity (p = 0.7). Conclusion: The results of this study indicate that there are no cerebral hemodynamic differences between TMB patients and hTIA patients. It is therefore unlikely that hemodynamic factors account for differences in clinical characteristics between the two patient groups.

Cerebral hemodynamics and metabolism in patients with symptomatic occlusion of the internal carotid artery

Background and Purpose— The goals of this study were to investigate (1) whether the concentrations of choline, creatine, and N-acetyl aspartate (NAA) in cerebral white matter are changed in patients with symptomatic occlusion of the internal carotid artery (ICA) and (2) whether possible changes in metabolite concentration are related to regional cerebral perfusion or cerebral vasoreactivity. Methods— In 19 patients (mean±SD age, 60±9 years), white matter metabolite concentrations were measured with proton MR spectroscopic imaging on average 4±2 months after symptoms occurred. In selected voxels, corresponding cerebral blood flow and volume, mean transit time, and time-to-bolus peak were determined with dynamic susceptibility contrast MRI. Cerebral CO2 reactivity was determined with transcranial Doppler sonography. Results— No significant changes in choline and creatine concentrations were observed. NAA concentration was significantly reduced in the hemisphere on the side of the symptomatic ICA (9.1±1.7 mmol/L) compared with the contralateral hemisphere (10.5±1.7 mmol/L, P <0.005) and control subjects (10.5±0.9 mmol/L, P <0.01). Although no significant interhemispheric difference in NAA concentration was found in patients who presented with retinal ischemia, patients with cerebral ischemia had a significantly lower NAA concentration in the symptomatic hemisphere (9.0±1.7 mmol/L) compared with the asymptomatic hemisphere (10.4±1.6 mmol/L, P <0.05). In all patients, NAA concentration was not significantly correlated with quantitative cerebral perfusion parameters or CO2 reactivity. Conclusions— Patients with symptomatic ICA occlusion may show chronic neuronal damage in cerebral white matter as evidenced by reduced NAA concentration. This seems to be related to previous symptomatology rather than to the cerebral hemodynamic status in a chronic stage.