The silent brain infarct before and after carotid surgery

Silent cerebral ischemia detected by diffusion-weighted MRI after carotid endarterectomy

BACKGROUND AND PURPOSE

Small emboli arising from a friable plaque during carotid endarterectomy (CEA) constitute an important risk of perioperative ischemic complications. To evaluate the incidence and significance of silent cerebral ischemic lesions of embolic origin after CEA, we prospectively examined a series of surgical patients with high-grade carotid stenosis by using diffusion-weighted MRI (DWI). We also tried to correlate postoperative ischemic lesions with the occurrence of sonographic cerebral embolic signals, the presence of plaque ulcerations, and the use of intraoperative shunting.

METHODS

Of a consecutive series of 53 patients undergoing elective CEA for high-grade carotid stenosis, 48 patients with unchanged postoperative neurological status were prospectively studied with DWI of the brain the day before and the day after the operation. The magnetic resonance images were analyzed by 2 neuroradiologists blinded to the clinical result of the operation. Any new hyperintense signal was interpreted as a postoperative ischemic lesion.

RESULTS

Forty-six (95.8%) of 48 patients had unchanged postoperative brain DWI. In 2 patients (4.2%), a new single asymptomatic hyperintense signal was observed on the side of the operation. Both lesions were small and presumably of embolic origin. They were not related to sonographic embolic signals, plaque ulcerations, or intraoperative shunting.

CONCLUSIONS

These results suggest that the incidence of silent ischemic brain lesions of embolic origin after CEA is low and does not correlate with the occurrence of intraoperative sonographic microemboli. They confirm that CEA is a safe procedure that carries a low risk of postoperative cerebral events.

Cerebral tomographic findings in patients undergoing carotid endarterectomy for asymptomatic carotid stenosis: short-term and long-term implications

PURPOSE

Preoperative cerebral imaging has been considered not to be cost-effective in carotid endarterectomy (CEA) for asymptomatic carotid stenosis. Yet, silent brain infarction (SBI) has been associated with the embolization potential of a severe carotid stenosis. Thus the presence of SBI may represent an additional indication for CEA in asymptomatic patients. We examined the predictive value of preoperatively detected silent cerebral lesions on early and late outcomes in patients undergoing CEA for asymptomatic carotid stenosis.

METHODS

Preoperative cerebral tomographic (CT) scans performed on 301 asymptomatic patients undergoing 346 CEAs from 1986 to 1995 were reviewed by a single neuroradiologist blinded to patients' records. Mean follow-up was 67. 3 months (range, 24-130 months). The degree of internal carotid lumen reduction was measured bilaterally in all patients (602 carotid arteries); carotid stenosis of 60% or more was found in 399 carotid arteries.

RESULTS

Of the 103 (34%) CT scans positive for cerebral lesions, 58% were lacunar. No significant association was observed between the side of the cerebral lesion on CT scan and the severity of the corresponding carotid stenosis; 38 silent lesions were detected in the 203 hemispheres ipsilateral to carotid stenoses that were less than 60% versus 95 SBIs in the 399 hemispheres ipsilateral to carotid stenoses that were 60% or more (19% vs 24%; P =.2). There were no significant differences in the perioperative stroke/death rate in patients with or without cerebral CT lesions (2% vs 1%; odds ratio, 1.94; P =.6). Mortality rate during follow-up was 22% in patients with preoperative SBI and 15% in patients without SBI (P =.1). However, actuarial survival at 10 years was shorter (P =.02) in patients with SBI. Late stroke occurred in 11% of patients with preoperative SBI and in 3% of patients without preoperative SBI (P =.006). Cox regression analysis showed that both preoperative lacunar and nonlacunar infarctions were independent predictors of late stroke (hazard ratio, 3.6; P =.04; and hazard ratio, 7.1; P =.001; respectively).

CONCLUSION

In our experience, preoperative SBI did not occur more frequently in the hemisphere ipsilateral to asymptomatic severe carotid stenosis. Although our study lacks a medically treated control group, our data show that SBI is predictive of poor neurologic outcome in asymptomatic patients undergoing CEA. We conclude that CT before CEA, selectively applied, provides information on long-term neurologic prognosis and that a less aggressive attitude towards CEA in asymptomatic patients with SBI may be justified.

Silent brain infarction on magnetic resonance imaging and neurological abnormalities in community-dwelling older adults. The Cardiovascular Health Study. CHS Collaborative Research Group

BACKGROUND AND PURPOSE

Infarctlike lesions are frequently detected in symptomatic and asymptomatic older persons undergoing cerebral MRI, but their significance in older adults has not been examined. We determined the prevalence of MRI infarcts in a population-based sample of men and women aged > or = 65 years and related these findings to demographic, cognitive, and neurological status.

METHODS

MRI scanning was performed in 3660 Cardiovascular Health Study (CHS) participants after brief neurological examinations and tests of cognitive function. MRIs were read centrally for the presence of an infarct > or = 3 mm in diameter or smaller infarctlike lesions.

RESULTS

MRI infarcts were detected in 1131 of 3647 participants with readable infarct information (31%) and in 961 of the subgroup of 3397 participants (28%) without known prior stroke ("silent" MRI infarcts). Smaller infarctlike lesions were found in 196 of 2516 participants who had no MRI infarcts > or = 3 mm. MRI infarcts were more common in participants who were older, had prior stroke, impaired cognition, visual field deficits, slowed repetitive finger tapping (all P < .0001), weakness on toe and heel walking, and history of memory loss, coma, or migraine headaches. Multivariate analysis in those without prior stroke showed strong associations of silent MRI infarcts with older age, history of migraines, lower digit symbol scores, and more abnormalities on neurological examination.

CONCLUSIONS

MRI evidence of brain infarction is common in older men and women without a clinical history of stroke. Their strong associations with impaired cognition and neurological deficits suggest that they are neither silent nor innocuous.

Silent lacunar infarcts in elderly patients with chronic non valvular atrial fibrillation

It is still debated whether non valvular atrial fibrillation (NVAF) may be responsible for "silent" lacunar lesions. The aims of our study were to compare the prevalence of subcortical lacunar infarctions in highly selected elderly subjects with or without NVAF, and to investigate the positive relationship of such lesions to the impairment in cognitive and physical functions. Thirty-eight patients with NVAF (mean age 80.6 years) were compared with 40 patients in sinus rhythm (mean age 80.4 years). Exclusion criteria were previous stroke or transient ischemic attacks, significant lesions of extracranial arteries, and any previous disease leading to cognitive impairment or potentially interfering with cognitive functions. A cranial computed tomogram was performed in every case, and the number of lacunae was recorded. Cognitive status and mood were assessed by means of Mini Mental Status Examination and the Geriatric Depression Scale, respectively. The number of impaired basic and instrumental activities of daily living (BADL e IADL) was also recorded. A significantly higher percentage of patients with lacunar lesions was detected in the NVAF group. The MMS score was lower in these patients, but did not reach significant levels. In univariate analysis, the presence of lacunae was found to be significantly associated with age, systolic blood pressure and atrial fibrillation, but, in a multiple logistic regression model, only age and atrial fibrillation retained a significant association. Similarly, in univariate analysis, a low MMS score was found to be related to age, systolic blood pressure, leukoaraiosis and both the presence and the number of lacunar lesions. In multivariate analysis, only age and the number of lacunae were significantly associated with a low MMS. It is concluded that in elderly patients NVAF is associated with subcortical ischemic lesions which may contribute to the impairment of cognitive function.

Computerised tomography findings as a risk factor in carotid endarterectomy: early and late results

OBJECTIVES

To evaluate whether preoperative CT evidence of brain infarction is associated with an increased risk of early and late stroke and death in patients undergoing CEA.

DESIGN

Retrospective clinical study.

MATERIALS AND METHODS

We evaluated 844 CT scanning records from 893 patients undergoing CEA from 1986-1994: 43% (367) CT positive for cerebral infarction and 57% (477) negative. Univariate and multivariate analysis was performed for risk factors and preoperative symptoms in patients with positive and negative CT scans, and Kaplan Meier survival curves for late events.

RESULTS

A positive CT was significantly more frequent in males vs. females (p < 0.0001; O.R. 2.52; C.I. 1.73-3.73), diabetics vs. non-diabetics (p = 0.03; O.R. 1.52; C.I. 1.03-2.26), symptomatics vs. asymptomatics (p < 0.001; O.R. 2; C.I. 1.93-3.53) and contralateral occlusion vs. patency (p < 0.001; O.R. 2; C.I. 1.30-3.10). The perioperative disabling stroke/ death rate was higher in patients with a positive CT (p = 0.002; O.R. 6.27; C.I. 1.73-34.20); in asymptomatic patients this difference was striking (5 patients vs. O, p = 0.0002). Multiple logistic regression analysis for risk factors, CT findings, symptoms preceding surgery, and congruity of brain infarction confirmed a significantly higher incidence of perioperative stroke/death rate (p = 0.003; O.R. 6.37; C.I. 5.12-7.63) and early and late stroke (p = 0.02; O.R. 1.95; C.I. 1.38-2.53) and death (p = 0.0005; O.R. 2.38; C.I. 1.89-2.88) in patients with brain lesions. After 7 years, the survival rate (p = 0.0009) and stroke-free interval (p = 0.003) were lower in patients with a positive CT. After 5 years, in asymptomatic patients the survival rate (p = 0.003) and stroke-free interval (p = 0.01) were lower in the positive CT group.

CONCLUSIONS

A positive CT finding, regardless of congruity of the lesion, should be regarded as an indicator of an increased risk of stroke and death in patients scheduled for carotid surgery, especially in those with asymptomatic stenosis.

Clinical potential for the use of neuroprotective agents. A brief overview

"Stroke treatment seems to be entering a golden age ...." Fisher's observation not only applies to ischemic stroke, but to all the conditions described above, and in the future, possibly (and quite speculatively), to other neurologic diseases, such as multiple sclerosis, amyotrophic lateral sclerosis, even radiation therapy and Bell's palsy. Physicians must sharpen their criteria for decisions regarding therapy and must" ... be prepared to accept what is actually known from scientific data ... rather than to rely on instinct, clinical impression, or the need to do something rather than nothing."

Silent brain infarct after carotid artery surgery: incidence and prevention

To determine the prevalence and mechanisms of postoperative silent brain infarct, brain CT was routinely performed before and after carotid endarterectomy during the same period of hospitalization. Between June 1991 and May 1993, 69 patients who underwent 74 carotid endarterectomies (five two-staged bilateral procedures) were enrolled in the study. Ipsilateral brain infarct was observed on the preoperative CT scans in 25 cases. Of these 25 infarcts, three occurred in 20 patients (15%), without symptoms, 13 in 41 patients (32%) with transient ischemic attacks (TIAs), and 9 in 13 patients (70%) with cerebrovascular accident. After surgery, two patients (2.7% of procedures) had monoparesia of an upper limb with no corresponding abnormality seen on CT scans, and two (2.7%) had TIAs, associated with CT evidence of a new lesion in one patient. Five silent brain infarcts (6.8%) were detected, including four in the hemisphere contralateral to the restored carotid artery. These study results indicate there is no correlation between the occurrence of postoperative silent brain infarct and the presence of ulcerated stenosis of the carotid artery documented by Doppler ultrasound examination. Silent infarct was not observed in any of the 24 patients (32%) in whom a shunt had been used during the procedure. After a review of the literature, we propose wider use of intraoperative shunts to prevent postoperative silent brain infarct.

Baseline silent cerebral infarction in the Asymptomatic Carotid Atherosclerosis Study

BACKGROUND AND PURPOSE

In a group of patients with high-grade asymptomatic carotid artery stenosis, we prospectively determined the prevalence and radiological characteristics of clinically asymptomatic brain infarction evident on computed tomography. Risk factors and extent of carotid disease were also determined.

METHODS

Patients randomized into the Asymptomatic Carotid Atherosclerosis Study (ACAS) underwent a neurological history, a detailed stroke/transient ischemic attack questionnaire, and a detailed neurological examination. Computed tomography scans were examined by standardized criteria developed as part of a quality-control program supervised by a neuroradiologist. The presence, location, and size of all cerebral infarctions evident by computed tomography were determined.

RESULTS

Among 1132 patients, 848 had no history of stroke or transient ischemic attack. One hundred twenty-six patients (15%) had a silent infarct; 95 (11%) had one, 24 (3%) had two, and 7 (1%) had three or more infarcts. The infarct size was small and deep for 117 patients (72%), less than one-half lobe for 45 (28%), and one-half to less than one lobe for 1 (0.5%). The silent infarcts were evenly distributed ipsilaterally and contralaterally to the study artery but were significantly more frequent in the right hemisphere (P < .05). Factors associated with silent infarction were abnormal gait (P < .001), abnormal deep tendon reflexes or plantar responses (P = .038), but not degree of carotid stenosis. Silent infarction was less frequent among this totally asymptomatic cohort (15%) compared with those with transient ischemic attacks (34/139, 25%; P < .001).

CONCLUSIONS

Silent infarction in the setting of asymptomatic carotid stenosis is not uncommon, but silent infarctions are rarely sizable. The clinical significance of silent cerebral infarction in patients with asymptomatic carotid artery stenosis has yet to be established.

Silent brain infarctions in patients with first-ever stroke. A community-based study in Umbria, Italy

BACKGROUND AND PURPOSE

The relative frequency of computed tomographic evidence of old cerebral infarctions without prior history of stroke, and their effect on short- and long-term outcome of patients with first-ever ischemic stroke, are currently unknown. Silent infarctions may relate to specific risk factors and may influence the rate of survival free of handicap.

METHODS

We studied the prevalence of such lesions in patients registered with SEPIVAC, a community-based survey of stroke incidence and outcome in the Sixth Local Health Unit of Umbria, Italy. Of 375 first-ever strokes, 209 patients with cerebral infarction (computed tomogram done within 30 days after the stroke) were included in this study. Computed tomograms were reviewed blindly, and cases were classified as having a single lesion or multiple lesions; in the latter case, it was assumed that at least one silent brain infarction was present. The two groups were compared in terms of risk factors and outcome. To avoid a selection bias, these patients were also compared with 68 patients who were not submitted to computed tomography but were judged on clinical grounds to have a > 90% probability of having suffered a cerebral infarction.

RESULTS

Risk factors and outcome did not differ between patients without and with a computed tomogram. In the latter group, 80 patients (38.3%; 95% confidence interval, 31.7%-44.9%) had silent brain infarction. Male sex (odds ratio, 1.84; 95% confidence interval, 1-3.4), ischemic changes on an electrocardiogram (odds ratio, 2.5; 95% confidence interval, 1.3-4.9), and--in the multivariate analysis--hypertension (odds ratio, 1.46; 95% confidence interval, 1.1-2) were significantly more frequent in these patients. Outcome at 1, 6, and 12 months was not influenced by the presence of silent infarctions.

CONCLUSIONS

This community-based study shows that silent brain infarctions in patients with first-ever stroke are not significantly related to risk factors commonly described in hospital-based series (atrial fibrillation, transient ischemic attack, etc.); rather, silent infarctions seem to be a marker of widespread vascular disease.