Diffusion-weighted MRI: detection of cerebral ischemia before and after carotid thromboendarterectomy

Silent brain infarcts on diffusion-weighted imaging after carotid revascularisation: A surrogate outcome measure for procedural stroke? A systematic review and meta-analysis

Aim

To investigate whether lesions on diffusion-weighted imaging (DWI+) after carotid artery stenting (CAS) or endarterectomy (CEA) might provide a surrogate outcome measure for procedural stroke.

Materials and Methods

Systematic MedLine® database search with selection of all studies published up to the end of 2016 in which DWI scans were obtained before and within seven days after CAS or CEA. The correlation between the underlying log odds of stroke and of DWI+ across all treatment groups (i.e. CAS or CEA groups) from included studies was estimated using a bivariate random effects logistic regression model. Relative risks of DWI+ and stroke in studies comparing CAS vs. CEA were estimated using fixed-effect Mantel-Haenszel models.

Results

We included data of 4871 CAS and 2099 CEA procedures (85 studies). Across all treatment groups (CAS and CEA), the log odds for DWI+ was significantly associated with the log odds for clinically manifest stroke (correlation coefficient 0.61 (95% CI 0.27 to 0.87), p = 0.0012). Across all carotid artery stenting groups, the correlation coefficient was 0.19 (p = 0.074). There were too few CEA groups to reliably estimate a correlation coefficient in this subset alone. In 19 studies comparing CAS vs. CEA, the relative risks (95% confidence intervals) of DWI+ and stroke were 3.83 (3.17-4.63, p < 0.00001) and 2.38 (1.44-3.94, p = 0.0007), respectively.

Discussion

This systematic meta-analysis demonstrates a correlation between the occurrence of silent brain infarcts on diffusion-weighted imaging and the risk of clinically manifest stroke in carotid revascularisation procedures.

Conclusion

Our findings strengthen the evidence base for the use of DWI as a surrogate outcome measure for procedural stroke in carotid revascularisation procedures. Further randomised studies comparing treatment effects on DWI lesions and clinical stroke are needed to fully establish surrogacy.

Perioperative ischemic complications of the brain after carotid endarterectomy

BACKGROUND

The potential morbidity of cerebral ischemia after carotid endarterectomy (CEA) has been recognized, but its reported incidence varies widely.

OBJECTIVE

To prospectively evaluate the development of cerebral ischemic complications in patients treated by CEA at a high-volume cerebrovascular center.

METHODS

Fifty patients with moderate or severe carotid stenosis awaiting CEA were studied with perioperative diffusion-weighted imaging of the brain and standardized neurological evaluations. Microsurgical CEA was performed by 1 of 2 vascular neurosurgeons. Radiological studies were evaluated by faculty neuroradiologists who were blinded to the details of the clinical situation.

RESULTS

Preoperative diffusion-weighted imaging studies were performed within 24 hours of surgery. A second study was obtained within 24 (92% of patients), 48 (4% of patients), or 72 (4% of patients) hours after surgery. Intraluminal shunting was used in 1 patient (2%), and patch angioplasty was used in 2 patients (4%). No patient had diffusion-weighted imaging evidence of procedure-related cerebral ischemia. Nonischemic complications consisted of postoperative confusion in an 87-year-old man with a urinary tract infection and a marginal mandibular nerve paresis in another patient. Radiological studies were normal in both patients.

CONCLUSION

CEA is a relatively safe procedure that may be performed with an acceptable risk of cerebral ischemia in select patients. The low rate of ischemic complications associated with CEA sets a standard to which other carotid revascularization techniques should be held. The current results are presented with a discussion of the senior author's preferred surgical technique and a brief review of the literature.

Embolic complications after carotid artery stenting or carotid endarterectomy are associated with tissue characteristics of carotid plaques evaluated by magnetic resonance imaging

BACKGROUND

Unstable carotid plaques are associated with an increased incidence of embolic complications after carotid artery stenting (CAS) or carotid endarterectomy (CEA). The aim of this study was to elucidate the relationship between the tissue components of carotid plaques and the incidence of new ipsilateral silent ischemic lesions (NISIL) after CAS or CEA.

METHODS

We performed CAS in 56 patients and CEA in 25 patients. We also performed quantitative analyses of carotid plaque characteristics before treatment using T1 weighted black-blood magnetic resonance imaging (BB-MRI). The signal intensity ratio (SIR) was defined as the ratio of signal intensity evaluated by BB-MRI in carotid plaques to that of sternocleidomastoid muscle. According to criteria that we and other investigators previously reported, an SIR ≥ 1.25 was defined as "high". NISIL were evaluated by diffusion-weighted imaging of MRI before and after CAS or CEA.

RESULTS

In the high SIR group, the incidence of NISIL was significantly greater after CAS than after CEA (61% vs 13%, respectively, p=0.006), whereas there were no significant difference in NISIL after the two procedures when the SIR was <1.25 (21% vs 0%). In multivariate regression analysis, the independent predictors of NISIL were CAS (p=0.002), symptomatic stenosis (p=0.036) and the SIR (p=0.049).

CONCLUSIONS

Noninvasive quantitative tissue characterization of carotid plaques using BB-MRI is useful to determine the indication for CAS.

How to avoid complications associated with carotid angioplasty and stenting

Carotid angioplasty and stenting (CAS) has been proposed as an alternative to surgery and is now performed more frequently and is well accepted, at least for high surgical risk patients. However, complications and particularly embolic strokes, even with a meticulous technique, can occur at any step of the procedure. Silent embolism is detected after CAS and may be a problem that needs to be discussed. To avoid and reduce these complications associated with CAS, it is important to have good indications dependent upon on good patient and lesions selection, as well as correct technique. New parameters have been proposed, particularly for asymptomatic lesions. The authors consider that embolic protection devices (EPDs) are mandatory for CAS, and new techniques will be presented. The choice of the EPD depends on the clinical status of the patient, the lesion morphology and characteristics, and the anatomy of the artery. All stents are not equivalent and so a good choice of the stent is necessary to avoid and reduce the complications associated with CAS, and experienced operators are also needed. With all these considerations, CAS can now be performed with acceptable outcomes and in certain population the results are comparable or superior to surgery. The results of ongoing randomized trials are awaited.

New brain lesions after carotid stenting versus carotid endarterectomy: a systematic review of the literature

BACKGROUND AND PURPOSE

Against the background of a relatively low rate of clinical events during carotid angioplasty and stenting (CAS) or carotid endarterectomy (CEA), diffusion-weighted imaging (DWI) is increasingly being used to compare the incidence of new ischemic lesions after both procedures. In addition, DWI may also provide a means of defining the role of different CAS techniques on this adverse outcome. Therefore, we performed a PubMed search and systematically analyzed all peer-reviewed studies published between January 1990 and June 2007 reporting on the occurrence of new DWI lesions after CAS or CEA. Summary of Review- In 32 studies comprising 1363 CAS and 754 CEA procedures, the incidence of any new DWI lesion was significantly higher after CAS (37%) than after CEA (10%) (P<0.01). Similar results were obtained in a meta-analysis focusing on those studies directly comparing the incidence of new DWI lesions after either CEA or CAS (OR, 6.1; 95% CI, 4.19 to 8.87; P<0.01). The use of cerebral protection devices (33% vs 45% without; P<0.01) and closed-cell designed stents during CAS (31% vs 51% with open-cell stents; P<0.01), as well as selective versus routine shunt usage during CEA (6% vs 16%; P<0.01) significantly reduced the incidence of new ipsilateral DWI lesions.

CONCLUSIONS

New DWI lesions occur more frequently after CAS than after CEA. However, technical advances mainly in the field of endovascular therapy potentially reduce the incidence of these adverse ischemic events. In this scenario, DWI appears to be an ideal tool to compare and further improve both techniques.

New distal embolic protection device the FiberNet® 3 dimensional filter: First carotid human study

OBJECTIVE

Evaluate the performance and safety of the FiberNet Embolic Protection System during carotid artery intervention.

BACKGROUND

Carotid Angioplasty and Stenting (CAS) can be proposed to treat the majority of carotid stenoses. Brain embolization takes place and routine use of Embolic Protection Devices (EPD) is warranted. Many EPDs have significant limitations, which may be addressed by a new EPD, the FiberNet (Lumen Biomedical, Plymouth, MN).

METHODS

The system consists of a 3-dimensional expandable filter made of fibers, which expand radially, mounted onto a 0.014'' wire and retrieval catheter. FiberNet can capture particles as small as 40 microm without compromising flow.

RESULTS

35 lesions treated in 34 patients. Male 67.6%. Age: 71.4 +/- 8.8 (50-85). Average stenosis 84.5% +/- 7.9 (70-99). 29.4% were symptomatic. Technical success: 34/35 (97%). No stroke or death within 30 days. Neurological events: two permanent amaurosis, one amaurosis fugax. All samples visually contained significant amounts of emboli. The mean surface area of debris caught was 63.8 mm(2) (37.7-107.5). Comparisons were made with other EPDs. The mean surface area of debris caught was 12.2 mm(2) (2.7-34.3). No changes were noted in CT/MRI at 30-day post procedure.

CONCLUSION

The first human use of this new novel EPD in carotid artery stenting is encouraging. The FiberNet was easy to use and confirmed the ability to capture particles less than 100 microm. The feasibility of the FiberNet has been demonstrated. Additional patients will demonstrate the overall safety and efficacy of this new EPD device.

Predictive Implications of Recurrent Transient Ischemic Attacks in Large-Artery Atherosclerosis

BACKGROUND

It is uncertain whether recurrent transient ischemic attacks (R-TIAs), when comparing with single TIAs (S-TIAs), have any distinct mechanisms.

METHODS

All consecutive patients with TIAs, who had been admitted for a 2-year period, were divided into two groups: those who had R-TIAs and those who had S-TIAs. Registry data, medical records, and imaging findings were reviewed and compared between the two groups.

RESULTS

There were 85 patients who had TIAs: 42 patients had R-TIAs, and 43 patients had S-TIAs. On univariate analysis, R-TIA patients had less cardiac embolic TIA sources, less weakness, less speech disturbances, shorter symptom duration, a longer time interval from onset to treatment, less abnormalities on diffusion-weighted magnetic resonance imaging, and more significant relevant arterial stenoses. After logistic regression analysis, independent factors associated with R-TIAs were symptom duration < 10 min (odds ratio OR 3.62; 95% confidence interval CI 1.37-9.57), > or = 50% stenosis of the clinically relevant artery (OR 7.08; 95% CI 1.29-38.71), and absence of cardiac embolic sources (OR 0.04; 95% CI 0.002-0.71).

CONCLUSIONS

R-TIAs may have pathophysiological mechanisms distinct from those of S-TIAs and so may provide a clue for the etiologic diagnosis, in that patients with R-TIAs are more likely to have large-artery atherosclerosis.

Silent cerebral ischaemia: hidden fingerprints of invasive medical procedures

Cardiovascular and cerebrovascular disorders are the main cause of death and permanent disability worldwide. Improved diagnostic and therapeutic options for these diseases have led to increasing numbers of invasive procedures such as angiography, stent placement, and operations exceeding 4 million each year in the USA. Although clinical examinations suggest a relatively low risk for ischaemic complications affecting the brain, new magnetic resonance techniques have led to the awareness of much higher numbers of clinically silent ischaemic brain lesions. Diffusion-weighted MRI (DWI) has shown new ischaemic lesions in a substantial number of patients undergoing cardiac or carotid-artery surgery, and coronary or cerebral-angiographic interventions. The clinical impact of these "silent" ischaemic lesions within brain areas without primary motor, sensory, or linguistic function ("non-eloquent" brain areas) is debated. There is increasing evidence, however, that cumulative burden of ischaemic brain injury causes neuropsychological deficits or aggravates vascular dementia. Thus, DWI emerges as a valuable diagnostic method for the monitoring of periprocedural ischaemic events in the brain, and could be a surrogate parameter for optimising diagnostic and therapeutic vascular procedures in the future.

Diffusion-weighted magnetic resonance imaging in carotid angioplasty and stenting with balloon embolic protection devices

We compared the results of two procedures to protect against distal embolism caused by embolic debris from carotid angioplasty with stent deployment (CAS) using diffusion-weighted magnetic resonance imaging (MRI). The study group comprised 39 men and 3 women (42 and 3 CAS procedures, respectively) with severe carotid stenosis (average age 70.0 +/- 6.6 years). During 20 CAS procedures the internal carotid artery was protected with a single balloon. A PercuSurge GuardWire was used for temporary occlusion. During 25 CAS procedures the internal and external carotid arteries were simultaneously temporarily occluded with a PercuSurge GuardWire and a Sentry balloon catheter, respectively. Diffusion-weighted MRI was performed 1 to 3 days after CAS. Data from 26 patients undergoing conventional angiography for diagnosis of cerebral ischemic disease, cerebral aneurysm or brain tumors were included as controls. Diffusion-weighted MRI after conventional diagnostic angiography showed ischemic spots in 3 of the 26 controls (11.5%). Ischemic spots were observed during 11 of 20 CAS procedures with the internal carotid artery protected with a single balloon (55.0%), and were observed during 9 of 25 CAS procedures with both the internal and external carotid arteries protected (36.0%). This difference was significant (P = 0.0068). Ischemic lesions appeared not only ipsilateral to the carotid stenosis but also in the contralateral carotid artery (31.9%) and vertebrobasilar territory (25.3%). Better protection was obtained with simultaneous double occlusion of both the internal and external carotid artery than with single protection of the internal carotid artery during CAS.

Cerebral microembolization after protected carotid artery stenting in surgical high-risk patients: results of a 2-year prospective study

BACKGROUND

This was a prospective single-center study to assess and analyze cerebral embolization resulting from carotid artery stenting with neuroprotective filter devices in patients considered as poor surgical candidates for surgical carotid endarterectomy.

METHODS

Fifty-three consecutive patients with an internal carotid artery stenosis were treated by placement of carotid Wallstents with two different types of temporary distal filter protection devices: the Spider filter and the FilterWire. Diffusion-weighted magnetic resonance imaging (DWI) of the brain was obtained 24 hours before the procedure and within 5 to 30 hours after the procedure to detect ischemic brain lesions resulting from the procedure. Inclusion criteria were symptomatic (> or =70%) or asymptomatic (> or =80%) stenoses in surgical high-risk patients.

RESULTS

Two (4%) regressive minor strokes occurred. Postprocedural DWI detected new focal ischemic lesions in 21 patients (40%). The average number of lesions was 5.9 per patient, and the mean lesion volume was 1 mL or less in 19 patients (90%). Small differences were found in the lesion distribution: homolateral anterior circulation in eight cases (15.1%), other vascular territories in seven cases (13.2%), and homolateral anterior circulation plus other vascular territories in six cases (11.3%). The microembolization risk seemed nonpredictable on the basis of clinical parameters and internal carotid artery lesion characteristics. An increased risk in the rate of ipsilateral hemispheric embolization has been observed in difficult carotid arch implantations (P = .04).

CONCLUSIONS

The incidence of new focal ischemic lesions detected by DWI is higher than expected on the basis of previous reports. Embolization from the aortic arch or common carotid arteries could account for most of those events in patients considered as surgical high-risk patients. Although 90% of the events were clinically silent, this high rate of microembolization raises questions about the possible consequences on cerebral cognitive functions.

Risk factors for periprocedural complications in carotid artery stenting without filter protection

INTRODUCTION

In high-grade stenosis, carotid artery stenting (CAS) may be chosen as an alternative to carotid surgery. Ischemic periprocedural complications may be documented best with diffusion-weighted MRI (DWMRI). In this prospective study serial DW-MRI and color-coded duplex sonography (CCDS) were used to identify carotid stenosis, which is associated with an increased risk of ischemic events due to CAS.

METHODS

High resolution DW-MRI were performed in 74 out of 77 patients before and after CAS. All MRI scans were analyzed in a blinded manner. With CCDS each carotid stenosis was evaluated according to the grade, length, echo properties and plaque surface.

RESULTS

In 42 out of 74 patients (56.8 %) a total of 188 new procedure- related DWI-lesions could be detected, while in 32 patients MRI-controls remained normal. Of the lesions 79.25 % had a size < 1 cm. In one major and two minor strokes due to CAS (total complication rate 3.9 %) corresponding territorial infarcts could be demonstrated. A highly significant correlation was found between the length of the stenosis and the incidence of new DWI-lesions (p = 0.0141). In contrast, neither the grade of ICA stenosis nor the sonographic plaque morphology or plaque surface correlated with the number of DWI-lesion in postinterventional scans.

CONCLUSIONS

The length-and not the degree-of an ICA stenosis seems to be the most decisive sonographic factor for estimating the periprocedural risk of embolism. DWI-lesions are much more frequent than clinical complications and may represent an important surrogate marker for improving the techniques of carotid artery stenting, especially comparing the benefit of different mechanical protection devices.

Cerebral infarction: incidence and risk factors after diagnostic and interventional cardiac catheterization--prospective evaluation at diffusion-weighted MR imaging

PURPOSE

To prospectively evaluate incidence of clinically silent and clinically apparent embolic cerebral infarction following diagnostic and interventional coronary angiography and associated risk factors.

MATERIALS AND METHODS

Written informed consent was obtained from all patients, and the study was approved by the research ethics committee of University of Heidelberg, Germany. Fifty-two patients, including 37 men (mean age, 66.1 years +/- 11.9 [standard deviation]) and 15 women (mean age, 65.3 years +/- 10.3), undergoing elective cardiac catheterization were examined 3-26 hours (mean, 15.3 hours +/- 6) before and 12-48 hours (mean, 25.9 hours +/- 10.4) after cardiac catheterization. Magnetic resonance imaging protocol included isotropic and anisotropic diffusion-weighted single-shot echo-planar sequences. T2-weighted turbo spin-echo and T1-weighted spin-echo sequences also were performed. Apparent diffusion coefficient maps were calculated to exclude false-positive reading results on diffusion-weighted images because of T2 shine-through effect. Images were assessed by two experienced radiologists blinded to clinical data. Cardiac catheterization was performed by 11 experienced cardiologists to exclude operator-related risk. A neurologic examination according to the National Institutes of Health Stroke Scale and Barthel index was performed by a senior cardiologist before acquisition of each image. Sixteen clinical and angiographic variables were analyzed with univariate analysis for ability to predict occurrence of cerebral infarction.

RESULTS

No embolic cerebral lesions could be detected at diffusion-weighted imaging before catheterization. After coronary angiography, seven (15%) of 48 patients demonstrated nine focal cerebral infarcts affecting anterior and posterior circulation. Patients remained asymptomatic. Of all tested variables, only duration of the procedure was identified as an independent predictor of occurrence of cerebral infarction (P < .05).

CONCLUSION

In this prospective study, asymptomatic cerebral infarction following cardiac catheterization occurred in 15% of patients in whom duration of the procedure was significantly longer than in those without infarction (P = .017).

Cerebral ischemia after carotid intervention

PURPOSE

To determine the incidence of symptomatic and asymptomatic cerebral ischemic lesions found on diffusion-weighted magnetic resonance imaging (DW-MRI) after carotid interventions.

METHODS

A prospective study was conducted to assess new cerebral ischemic lesions using DW-MRI in symptomatic patients with carotid artery disease undergoing protected carotid artery stenting (CAS) or carotid endarterectomy (CEA). DW-MRI was performed before and after the intervention in 44 patients (21 CAS and 23 CEA). Two experienced radiologists not involved in the carotid procedures or neurological assessment compared the postprocedural DW-MR images with those acquired before the intervention.

RESULTS

Three (6.8%) of the 44 patients suffered strokes: 1 major and 1 minor stroke after CEA and 1 minor stroke after CAS. DW-MRI showed 15 new hyperintense lesions in 2 (9%) of 23 CEA patients; 31 new hyperintense lesions were found in 9 (43%) of the 21 CAS patients. The majority of new lesions were located in the ipsilateral vascular territory; 2 CAS patients also showed 6 new hyperintense lesions in the cerebellum. The mean lesion load per patient was 2.52 cm(3) (range 0.31-4.74) in the CEA group and 1.74 cm(3) (0.03-9.72) in the CAS group (p=0.35). The volume of the individual lesions in CEA patients was 0.39 cm(3) (range 0.01-2.16) compared to 0.52 cm(3) (range 0.01-5.47) in the CAS group (p=0.23). Patients who were asymptomatic after the intervention had fewer lesions (p=0.03) and a smaller lesion load than symptomatic patients.

CONCLUSIONS

Ischemic lesions were more frequently seen on DW-MRI after carotid stenting than after endarterectomy. The majority of the detected lesions did not cause neurological deficits.

Imaging of acute stroke: state of the art

The high incidence of stroke, plus its fatal or debilitating outcome, has prompted tremendous advances over the last two decades on both diagnostic and therapeutic fronts. Multiple randomized trials have proven the utility of thrombolytic agents with rejuvenation of the role of diagnostic imaging. State of the art imaging (mainly computed tomography and magnetic resonance imaging) is crucial for patient selection (eg, excluding intracranial hemorrhage), diagnosis of stroke and prediction of prognosis. Here, we discuss the anatomic and physiologic changes due to an ischemic insult as manifested by modern imaging techniques, including diffusion and perfusion imaging, as well as demonstration of vascular disease by cross sectional angiography supplemented by three dimensional postprocessing. The main target of management is "Penumbra", or salvageable tissue, which is primarily dependent upon the expediency of the whole process, better expressed by the phrase "Time is Brain".

New brain lesions at MR imaging after carotid angioplasty and stent placement

PURPOSE

To assess, with magnetic resonance (MR) imaging, the number and size of new brain lesions after carotid angioplasty and stent placement (CAS) and to evaluate the association of these new lesions with neurologic deficits and transcranial Doppler ultrasonographic (US) data.

MATERIALS AND METHODS

Seventy-two consecutive CAS procedures were performed in 72 patients. Patients underwent neurologic examination before, during, immediately after, and 1 day, 3 months, and 1 year after CAS. MR imaging was used before and after CAS to assess the number of symptomatic and silent new infarctions. Two radiologists reviewed all pre- and postintervention MR images. The radiologists were blinded to the clinical data.

RESULTS

Postprocedural MR images showed new lesions on the side of stent placement in 11 patients. In six patients, the new lesions were clinically silent. Two patients had a major stroke, one had a minor stroke, and two had transient ischemic attack. In patients who had had transient ischemic attack or stroke before CAS, the frequency of new lesions at postprocedural MR imaging was higher (23%) than in asymptomatic patients (12%); this difference was not statistically significant (P =.29). There was no statistically significant correlation between embolic load as detected with transcranial Doppler US monitoring and the occurrence of either clinical symptoms or new lesions seen at MR imaging.

CONCLUSION

CAS is associated with embolic events. The majority of new lesions seen on postintervention MR images are not detected at neurologic examination.