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S C Lewis

Publications and source records attributed to S C Lewis.

At least 19 recordsLinked to original sources
PubMed2006

No evidence that severity of stroke in internal carotid occlusion is related to collateral arteries.

BACKGROUND/AIM: The neurological effects of internal carotid artery (ICA) occlusion vary between patients. The authors investigated whether the severity of symptoms in a large group of patients with ipsilateral or/and contralateral ICA occlusion at presentation with ocular or cerebral ischaemic symptoms could be explained by patency of other extra or intracranial arteries to act as collateral pathways. METHODS: The authors prospectively identified all patients (n = 2881) with stroke, cerebral transient ischaemic attack (TIA), retinal artery occlusion (RAO), and amaurosis fugax (AFx) presenting to our hospital over five years, obtained detailed history and examination, and examined the intra and extracranial arteries with carotid and colour-power transcranial Doppler ultrasound. For this analysis, all those with intracranial haemorrhage on brain imaging and cerebral events without brain imaging were excluded. RESULTS: Among 2228/2397 patients with brain imaging (1713 ischaemic strokes, 401 cerebral TIAs, 193 AFx, and 90 RAO) who underwent carotid Doppler, 195 (9%) had ICA occlusion. Among those patients with cortical events, disease in potential collateral arteries (contralateral ICA, external carotid, ipsilateral or contralateral vertebral or intracranial arteries) was equally distributed among patients with severe and mild ischaemic presenting symptoms. CONCLUSION: The authors found no evidence that the clinical presentation associated with an ICA occlusion was related to patency of other extra or intracranial arteries to act as collateral pathways. Further work is required to investigate what determines the clinical effects of ICA occlusion.

Amaurosis Fugax↗
PubMed2003

Visible infarction on computed tomography is an independent predictor of poor functional outcome after stroke, and not of haemorrhagic transformation.

OBJECTIVES: To examine a very large dataset to provide a robust answer to the question of whether visible infarction on computed tomography was (a) an independent predictor of functional outcome at all times up to 48 hours after stroke, and (b) independently associated with haemorrhagic transformation, with or without antithrombotic treatment. METHODS: The study assessed associations between visible infarction, time to randomisation, baseline neurological deficit, stroke syndrome, allocated aspirin or heparin treatment, recurrent haemorrhagic stroke, early death and six month functional outcome in the International Stroke Trial. RESULTS: Of 12 550 patients, 6267 (50%) had visible infarction up to 48 hours after stroke. The prevalence of visible infarction increased with increasing time from onset and extent of the stroke syndrome. Visible infarction was independently associated with increased death within 14 days (odds ratio (OR) 1.17, 95% CI 1.02 to 1.35), and of death or dependency at six months (OR 1.42, 95% CI 1.31 to 1.55), an absolute increase of 13%, or 130 per 1000 more dead or dependent patients with visible infarction than without it. There was no significant independent relation between visible infarction and fatal or non-fatal haemorrhagic transformation, or interaction between visible infarction and aspirin or heparin treatment allocation with six month functional outcome. CONCLUSIONS: Visible infarction on computed tomography up to 48 hours after stroke is an independent adverse prognostic sign.

Aged↗
PubMed2002

Interobserver variability of magnetic resonance angiography in the diagnosis of carotid stenosis--effect of observer experience.

Magnetic resonance angiography (MRA) for determining the degree of carotid stenosis prior to carotid endarterectomy is attractive because it does not have the high morbidity associated with conventional intra-arterial angiography. We assessed the interobserver variability in the estimation of the degree of stenosis amongst observers of different experience. In a prospective study, consecutive patients with transient ischaemic attacks and symptomatic tight carotid stenosis shown by Doppler ultrasound underwent conventional intra-arterial angiography and 2-D and 3-D time-of-flight MRA of the carotid bifurcations. The films of the processed MRA images were reviewed blind to other clinical and imaging data by eight observers of different levels of experience and coded for the presence and degree of stenosis. The stenosis on intra-arterial angiography was used as the reference standard. There was considerable variability between observers for estimation of the degree of stenosis on MRA. The observers' accuracy ranged from 41% (student) to 79% (experienced). From these estimations, excluding those of the student, it could be seen that up to 23% of patients who would have had an endarterectomy based on MRA should not have done so according to angiography, and up to 33% of patients who should have had an endarterectomy according to angiography would have inappropriately missed having an endarterectomy based on MRA results. Observer reliability of MRA processed images is not good, even in experienced hands. Using the source images and views of the circle of Willis might improve the accuracy, but a further study is required to assess this.

Carotid Artery, Internal↗
PubMed2002

Severe ipsilateral carotid stenosis and middle cerebral artery disease in lacunar ischaemic stroke: innocent bystanders?

OBJECTIVES: Lacunar infarcts are thought to be mostly due to intracranial small vessel disease. Therefore, when a stroke patient with a relevant lacunar infarct does have severe ipsilateral internal carotid artery (ICA) or middle cerebral artery (MCA) disease, it is unclear whether the arterial disease is causative or coincidental. If causative, we would expect ICA/MCA disease to be more severe on the symptomatic side than on the asymptomatic side. Therefore, our aim was to compare the severity of ipsilateral with contralateral ICA and MCA disease in patients with lacunar ischaemic stroke. METHODS: We studied 259 inpatients and outpatients with a recent lacunar ischaemic stroke and no other prior stroke. We used carotid Duplex ultrasound and transcranial Doppler (TCD) ultrasound to identify ICA and MCA disease, and compared our results with previously published data. RESULTS: In our study, there was no difference between the severity of ipsilateral and contralateral ICA stenosis within individuals (median difference 0%, Wilcoxon paired data p=0.24, comparing severity of ipsilateral and contralateral stenosis). The overall prevalence of severe ipsilateral stenosis was 5%, and the prevalence of severe contralateral stenosis was 4% (OR 1.6, 95% CI 0.6, 4.8). There was no difference in the prevalence of ipsilateral and contralateral MCA disease. A systematic review of the other available studies strengthened this conclusion. CONCLUSION: Carotid stenosis in patients with a lacunar ischaemic stroke may be coincidental. Further studies are required to elucidate the causes of lacunar stroke, and to evaluate the role of carotid endarterectomy.

Carotid Stenosis↗
PubMed2002

Dose-response relationships between individual nonaspirin nonsteroidal anti-inflammatory drugs (NANSAIDs) and serious upper gastrointestinal bleeding: a meta-analysis based on individual patient data.

AIMS: To define by amalgamation of data obtained in contemporaneous case-control studies, the risks associated with individual nonaspirin nonsteroidal anti-inflammatory drugs (NANSAIDs) according to doses used. METHODS: Meta-analysis of individual patient data from three retrospective case-control studies using similar data collection protocols was carried out in hospitals in Catalonia, England, Scotland and Sweden. 2472 cases of upper gastrointestinal bleeding and 5877 controls were studied. Main outcome measures were risks associated with individual NANSAIDs according to dose used and the period of time for which they were given. RESULTS: Ibuprofen showed the lowest odds ratio (OR = 1.7; 95% confidence interval 1.1, 2.5), followed by diclofenac (4.9; 3.3, 7.1), indomethacin (6.0; 3.6, 10.0), naproxen (9.1; 6.0-13.7), piroxicam (13.1; 7.9-21.8) and ketoprofen (34.9; 12.7, 96.5). Striking dose-response relationships were seen with four to eight-fold increases in risk within conventionally used dose ranges for all except ketoprofen, where numbers were too few to allow dose analysis. Across the class, risk was highest during the first week of use (11.7; 6.5, 21.0), decreased thereafter with continuing use (5.6; 4.6, 7.0), and fell to 3.2 (2.1, 5.1) 1 week after discontinuing use. Concurrent use of more than one NANSAID substantially increased risk. CONCLUSIONS: The risk of upper gastrointestinal bleeding with NANSAIDs varies twenty-fold depending on the drug, and by three to seven-fold depending on the dose chosen. Risk is maximal during the first week and decreases thereafter. Paracetamol (acetaminophen) is not associated with upper gastrointestinal bleeding at any dose and should be the first-line analgesic wherever possible.

Aged↗
PubMed2002

Outcome, observer reliability, and patient preferences if CTA, MRA, or Doppler ultrasound were used, individually or together, instead of digital subtraction angiography before carotid endarterectomy.

OBJECTIVES: To evaluate the accuracy of routinely available non-invasive tests (spiral computed tomographic angiography (CTA), time of flight magnetic resonance angiography (MRA), and colour Doppler ultrasound (DUS)), individually and together, compared with intra-arterial digital subtraction angiography (DSA) in patients with symptomatic tight carotid stenosis; and to assess the effect of substituting non-invasive tests for DSA on outcome, interobserver variability, and patient preference. METHODS: Patients referred from a neurovascular clinic were subjected prospectively to DUS imaging. The operator was blind to symptoms. Patients with a tight carotid stenosis on the symptomatic side were admitted for DSA. CTA and MRA were performed during the admission. The CTA, MRA, and DSA films were each read independently by two of six experienced radiologists, blind to all other data. RESULTS: 67 patients were included (34 had all four imaging procedures). DUS, CTA, and MRA all agreed with DSA in the diagnosis of operable v non-operable disease in about 80% of patients. CTA tended to underestimate (sensitivity 0.65, specificity 1.0), MRA to overestimate (sensitivity 1.0, specificity 0.57), and DUS to agree most closely with (sensitivity 0.85, specificity 0.71) the degree of stenosis as shown by DSA. When using any two of the three non-invasive tests in combination, adding the third if the first two disagreed would result in very few misdiagnoses (about 6%). MRA had similar interobserver variability to CTA (both worse than DSA). Patients preferred CTA over MRA and DSA. CONCLUSIONS: DUS, CTA, and MRA all show similar accuracy in the diagnosis of symptomatic carotid stenosis. No technique on its own is accurate enough to replace DSA. Two non-invasive techniques in combination, and adding a third if the first two disagree, appears more accurate, but may still result in diagnostic errors.

Carotid Stenosis↗
PubMed2002

Prevalence of adults with brain arteriovenous malformations: a community based study in Scotland using capture-recapture analysis.

OBJECTIVE: To conduct a population based study of brain arteriovenous malformation (AVM) prevalence. METHODS: Multiple, overlapping sources of case ascertainment were used to establish the point prevalence of brain AVMs in the adult population of the Lothian health board of Scotland. Patients were sought retrospectively from all local general (family) practitioners, neurologists, neurosurgeons, stroke physicians, the specialist AVM clinic at the regional neuroscience centre, and routine coding of hospital discharge data. Case notes, brain imaging, and pathology reports were reviewed to validate each patient's diagnosis and to ensure that each was alive, over the age of 16 years, and resident in the geographical area of the study on the prevalence date of 30 June 1998. RESULTS: Of 148 potentially eligible people, 93 adults met the inclusion criteria. There were 40 women and 53 men. Men were significantly younger than women on the prevalence date (median age 39 years v 51 years, p = 0.003). Of those included, 25 (27%) had radiological evidence of prior therapeutic obliteration of their brain AVM and 9 (10%) had coexisting aneurysms. The minimum crude brain AVM prevalence was 15 per 100 000 adults and capture-recapture analysis gave an ascertainment adjusted prevalence of 18 (95% confidence interval 16 to 24) per 100 000 adults. CONCLUSIONS: The minimum estimate of brain AVM prevalence helps to assess its burden and comparative epidemiology and stresses the importance of brain AVMs as a cause of long term disability in adults.

Adult↗
PubMed2002

Are functional motor and sensory symptoms really more frequent on the left? A systematic review.

OBJECTIVES: To test the hypothesis that unilateral motor and sensory symptoms unexplained by identifiable disease are more common on the left side of the body than the right. METHODS: Systematic review of the literature published since 1965. RESULTS: 121 eligible studies, involving 1139 patients, were analysed. The pooled proportion of functional left sided weakness and sensory symptoms in adults was 58% (95% confidence interval (CI) 55 to 61%). A much higher proportion of left sided symptoms (66%, 95% CI 61 to 71%) was found in studies where laterality featured in the title of the paper. However, when laterality was not mentioned in the title, no significant difference between left and right was observed (53% on the left, 95% CI 48 to 57%). This difference could not be explained on the basis of sex differences between the groups or the date of the study. Functional or "psychogenic" movement disorder was right sided in 68% (95% CI 61 to 75%). Handedness did not influence symptom lateralisation. CONCLUSIONS: The findings of this systematic review question whether functional weakness and sensory symptoms do in fact occur more commonly on the left side of the body. A type of outcome variable reporting bias in combination with non-blinding of investigators may be responsible for this long held but erroneous belief.

Aged↗
PubMed2001

A high-resolution radiation hybrid map of the human genome draft sequence.

We have constructed a physical map of the human genome by using a panel of 90 whole-genome radiation hybrids (the TNG panel) in conjunction with 40,322 sequence-tagged sites (STSs) derived from random genomic sequences as well as expressed sequences. Of 36,678 STSs on the TNG radiation hybrid map, only 3604 (9.8%) were absent from the unassembled draft sequence of the human genome. Of 20,030 STSs ordered on the TNG map as well as the assembled human genome draft sequence and the Celera assembled human genome sequence, 36% of the STSs had a discrepant order between the working draft sequence and the Celera sequence. The TNG map order was identical to one of the two sequence orders in 60% of these discrepant cases.

Algorithms↗
PubMed2001

How does the degree of carotid stenosis affect the accuracy and interobserver variability of magnetic resonance angiography?

OBJECTIVES: The accuracy of magnetic resonance angiography (MRA) was determined in patients with recently symptomatic tight (80%-99%) carotid stenosis (on Doppler ultrasound), and the effect of stenosis severity on the accuracy and interobserver variability of MRA was studied. METHODS: Forty four consecutive patients undergoing intra-arterial angiography (IAA) before carotid endarterectomy were prospectively studied, in two centres with identical MR scanners and sequences. All patients had undergone Doppler ultrasound, showing a 70% or worse carotid stenosis on the symptomatic side. MRA and IAA were done during the same admission. The MRA films were each independently and blindly read for percentage stenosis (signal gap if present) by four observers. The IA angiograms were read separately by one observer, blind to symptoms, and Doppler and MRA results. RESULTS: Signal gaps on MRA were seen in stenoses ranging from 67% to 99% on intra-arterial angiography. Magnetic resonance angiograms consistently overestimated the percentage stenosis according to intra-arterial angiography. Clinically significant misclassification of stenosis occurred according to MRA in 7% of patients, and was more frequent as carotid stenosis increased. CONCLUSION: Significant diagnostic errors occur with MRA in patients with tight carotid stenosis. Any morbidity occurring as a result of misclassification by MRA is likely to be offset by the avoidance of complications; however, this could only be determined with certainty in a randomised controlled trial.

Analysis of Variance↗
PubMed2001

Variations between countries in outcome after stroke in the International Stroke Trial (IST).

BACKGROUND AND PURPOSE: This study describes the large variations in outcome after stroke between countries that participated in the International Stroke Trial and seeks to define whether they could be explained by variations in case mix or by other factors. METHODS: We analyzed data from the 15 116 patients recruited in Argentina, Australia, Italy, the Netherlands, Norway, Poland, Sweden, Switzerland, and the United Kingdom: We compared crude case fatality and the proportion of patients dead or dependent at 6 months; we used logistic regression to adjust for age, sex, atrial fibrillation, systolic blood pressure, level of consciousness, and number of neurological deficits. We used the frequency of prerandomization head CT scan and prescription of aspirin at discharge to indicate quality of care. RESULTS: The differences in outcome (all treatment groups combined) between the "best" and "worst" countries were very large for death (171 cases per 1000 patients) and for death or dependency (375 cases per 1000 patients). The differences were somewhat smaller after adjustment for case mix (160 and 311 cases per 1000 patients, respectively). Process of care may have accounted for some but not all of the residual variation in outcome. CONCLUSIONS: Adjustment for case mix explained only some of the variation in outcome between countries. The residual differences in outcome were too large to be explained by variations in care and most likely reflect differences in unmeasured baseline factors. These findings demonstrate the need to achieve balance of treatment and control within each country in multinational randomized controlled stroke trials and the need for caution in the interpretation of nonrandomized comparisons of outcome after stroke between countries.

Aged↗
PubMed2001

Negative attitudes among short-term stroke survivors predict worse long-term survival.

BACKGROUND AND PURPOSE: Patients respond to serious illness in different ways. We wished to determine whether different attitudes toward illness are associated with survival after stroke. METHODS: Three hundred seventy-two stroke patients were identified and medically assessed as part of a randomized trial to evaluate a stroke family care worker. They had all survived 6 months from randomization. A research psychologist visited each patient and administered the Mental Adjustment to Stroke Scale (a self-rated attitude scale based on the Mental Adjustment to Cancer Scale). Disability and dependence (Barthel Index, modified Rankin Scale) and mood (Hospital Anxiety and Depression Scale, General Health Questionnaire 30) were also assessed. Patients were followed up in 1998 (3 to 5 years after the initial stroke) to establish their survival. We modeled the relationship between Mental Adjustment to Stroke scores and survival, adjusting for other factors associated with stroke survival. RESULTS: Eighty-two patients (22%) died within 3 years. After adjustment for other significant factors, fatalism and helplessness/hopelessness were both associated with decreased survival (P=0.03 and 0.04, respectively), but fighting spirit, anxious preoccupation, and denial/avoidance were not. Mood was not associated with survival. CONCLUSIONS: Patients' attitudes toward their illness seem to be associated with survival after stroke. Patients who feel that there is nothing they can do to help themselves 6 months after a stroke have a shorter survival. These findings need to be confirmed and any causal relationship between attitude and survival further explored in a randomized controlled trial to "improve" the attitude of stroke patients toward their illness.

Aged↗
PubMed2000

Variability in Doppler ultrasound influences referral of patients for carotid surgery.

OBJECTIVE: Colour Doppler ultrasound is operator dependent, but it is unclear how much clinical impact this might have on patient referral for carotid endarterectomy. Our aim was to quantify the interobserver variability of Doppler ultrasound. METHODS: Consecutive patients attending for carotid Doppler ultrasound underwent two examinations on the same day, in random order, by two of three observers blind to each other's results. Severity of stenosis was assessed using standard velocity criteria and lesion appearance. RESULTS: A total of 189 patients were scanned (378 ICAs). Of the 134 ICAs scanned by observers 1 and 2, observer 1 classified 11 as 80-99% stenosis (operable), compared with nine by observer 2. Of the 206 ICAs scanned by observers 1 and 3, observer 1 classified 11 as 80-99% stenosis, compared with only five by observer 3. Of the 38 ICAs scanned by observers 2 and 3, observer 2 classified 2 as 80-99% stenosis compared with none by observer 3. Overall, clinical management would differ in 10/378 (3%) of ICAs, but in 10/22 (45%) of those considered operable by one of the three observers. CONCLUSION: There was clinically important interobserver variability in the assessment of ICA disease, which could result in serious errors if endarterectomy were performed on the basis of a single Doppler ultrasound.

Blood Flow Velocity↗
PubMed2000

How well does the Oxfordshire community stroke project classification predict the site and size of the infarct on brain imaging?

OBJECTIVES: The Oxfordshire Community Stroke Project (OCSP) classification is a simple clinical scheme for subdividing first ever acute stroke. Several small studies have shown that when an infarct is visible on CT or MRI, the classification predicts its site in about three quarters of patients. The aim was to further investigate this relation in a much larger cohort of patients in hospital with ischaemic stroke. METHODS: Between 1994 and 1997, inpatients and outpatients with ischaemic stroke were assessed by one of several stroke physicians who noted the OCSP classification. A neuroradiologist classified the site and extent of recent infarction on CT or MRI. RESULTS: Of 1012 patients with ischaemic stroke, 655 (65%) had recent visible infarcts. These radiological lesions were appropriate to the clinical classification in 69/87 (79%) patients with a total anterior circulation syndrome, 213/298 (71%) with a partial anterior circulation syndrome, 105/144 (73%) with a lacunar syndrome, and 105/126 (83%) with a posterior circulation syndrome. Overall, 75% of patients with visible infarcts were correctly classified clinically. If patients without a visible infarct did have an appropriate lesion in the brain (best case), the classification would have correctly predicted its site and size in 849/1012 (84%) patients, compared with only 492/1012 (49%) in the worst case scenario. CONCLUSION: The OCSP classification predicted the site of infarct in three quarters of patients. When an infarct is visible on brain imaging, the site of the infarct should guide the use of further investigations, but if an infarct is not seen, the OCSP classification could be used to predict its likely size and site.

Aged↗
PubMed2000

Relationship between pattern of intracranial artery abnormalities on transcranial doppler and Oxfordshire Community Stroke Project clinical classification of ischemic stroke.

BACKGROUND AND PURPOSE: The Oxfordshire Community Stroke Project (OCSP) devised a simple classification for acute stroke based on clinical features only, which is of value in predicting prognosis. We investigated whether the pattern of intracranial vascular abnormalities is related to the clinical syndrome. METHODS: Patients with acute ischemic stroke were classified by a stroke physician as having total or partial anterior circulation infarct (TACI or PACI, respectively), lacunar infarct (LACI), or posterior circulation infarct (POCI). Color-coded power transcranial Doppler was done whenever possible. Intracranial arterial velocities were compared in the 4 subtypes of ischemic stroke after adjustment for age and time to transcranial Doppler. RESULTS: Middle cerebral artery velocity was abnormal (hyperemia, reduced velocity, occlusion, or focal stenosis) in 38 of 69 TACIs (55%), 50 of 171 PACIs (29%), and 20 of 236 LACIs or POCIs (8%) (P<0.001). Velocity in the A1 segment of the anterior cerebral artery was reversed in 12 of 69 TACIs (17%), 20 of 171 PACIs (12%), and 8 of 236 LACIs or POCIs (3%) (P<0.001). Basilar artery velocity was abnormal in 8 of 121 POCIs (7%) compared with 5 of 355 (1%) of the other subtypes (P=0.005). Vertebral artery velocity was abnormal (reduced velocity, occlusion, stenosis) in 20 of 121 POCIs (17%) compared with 20 of 355 others (6%) (P=0.01). CONCLUSIONS: Intracranial arterial abnormalities were related to OCSP clinical subtype. Therefore, it is possible to stratify patients according to OCSP classification in trials of new treatments in which treatment effectiveness may depend on the underlying pattern of arterial pathology and before any arterial imaging is available.

Aged↗
PubMed1999

The influence of randomized trials on the use of anticoagulants for atrial fibrillation.

INTRODUCTION: Anticoagulants and anti-platelet drugs have been shown in randomized trials to reduce the risk of stroke in patients with atrial fibrillation (AF). We therefore investigated their use in patients known to be in AF before a stroke, transient ischaemic attack (either cerebral or ocular) or retinal artery occlusion to assess the influence of trials on clinical practice. METHODS: Inpatients and outpatients with acute stroke, transient ischaemic attack or retinal artery occlusion were prospectively identified by a stroke physician from 1990 to 1997. The presence or absence of AF before the vascular event, and prior use of anticoagulant and anti-platelet drugs were recorded at the time of the assessment and verified using information from general practitioner and hospital case notes. RESULTS: Of 1934 patients with stroke or retinal artery occlusion, 191 (10%) were in AF before their ischaemic event. Anticoagulants had been used in 40 (21%) of these, but only in 32 (2%) of the 1743 patients in sinus rhythm [odds ratio (OR) 14.2, 95% confidence interval (CI) 8.6-23.2]. Anti-platelet drugs had been used in 62 (32%) of those with AF compared with 500 (30%) of those in sinus rhythm (OR 1.2, 95% CI 0.9-1.64). Of the 161 patients in AF without contraindications to anticoagulants, only 36 (22%) were taking them. Although there was a statistically significant increase in anticoagulant use from 8% in 1990 to 23% in 1996, this could be explained solely by a fall in the age of the patients referred to our hospital. CONCLUSION: Anticoagulation is probably under-used in AF. We found no conclusive evidence that anticoagulation trials have influenced clinical practice. This raises issues about the dissemination and implementation of trial results.

Aged↗