MRI of carotid atherosclerosis to identify TIA and stroke patients who are at risk of a recurrence.

PURPOSE: To evaluate the potential of carotid plaque MRI to predict transient ischemic attack (TIA) and stroke recurrence in previously symptomatic patients. MATERIALS AND METHODS: One hundred twenty-six TIA/stroke patients with ipsilateral 30-69% carotid stenosis underwent multisequence carotid plaque MRI. The presence of a lipid-rich necrotic core (LRNC), fibrous cap (FC) status, and intraplaque hemorrhage (IPH) were assessed. Patients were followed to determine the recurrence of ipsilateral TIA and/or stroke within 1 year after inclusion. RESULTS: Thirteen patients suffered from recurrent ipsilateral clinical ischemic events (10 TIAs and 3 strokes). Carotid stenosis grade was not associated with recurrent events (hazard ratio [HR] for 50-69% versus 30-49% stenosis = 1.198; 95% confidence interval [CI], 0.383 to 3.749; P = 0.756). The presence of an LRNC (HR = 3.2001; 95% CI, 1.078 to 9.504; P = 0.036), a thin and/or ruptured FC (HR = 5.756; 95% CI, 1.913 to 17.324; P = 0.002), and IPH (HR = 3.542; 95% CI, 1.058 to 11.856; P = 0.040) were associated with recurrence. CONCLUSION: The presence of MRI-depicted LRNC, a thin and/or ruptured FC, and IPH are associated with the recurrence of clinical cerebrovascular ischemic events in TIA and stroke patients with carotid atherosclerosis.

Longitudinal MRI study on the natural history of carotid artery plaques in symptomatic patients.

PURPOSE: To investigate the natural history of carotid atherosclerosis in patients who experienced a TIA or ischemic stroke. PATIENTS AND METHODS: Ninety-two TIA/stroke patients (57 men, mean age 67.7 ± 9.8 years) with ipsilateral <70% carotid stenosis underwent multisequence MRI of the plaque ipsilateral to the symptomatic side at baseline and after one year. For each plaque, several parameters were assessed at both time points. RESULTS: Carotid lumen, wall and total vessel ( = carotid lumen and wall) volume did not significantly change. Forty-four patients had a plaque with a lipid-rich necrotic core (LRNC) at baseline, of which 34 also had a LRNC after one year. In three patients a LRNC appeared after one year. Thirty patients had a plaque with a thin and/or ruptured fibrous cap (FC) at both time points. In seven patients, FC status changed from thin and/or ruptured into thick and intact. In three patients, FC status changed from thick and intact into thin and/or ruptured. Twenty patients had intraplaque hemorrhage (IPH) at both time points. In four patients, IPH disappeared, whereas in three patients, new IPH appeared at follow-up. CONCLUSION: In TIA/stroke patients, carotid plaque morphology does not significantly change over a one-year period. IPH and FC status change in a minority of patients.

The effectiveness of thrombolysis with intravenous alteplase for acute ischemic stroke in daily practice.

BACKGROUND: Thrombolysis with intravenous alteplase has been proven an effective treatment for patients with acute ischemic stroke in randomized clinical trials. In daily practice, the effect of thrombolysis may be less, and complications may occur more often. AIMS: The aim of this study was to assess effectiveness and safety of thrombolysis in an unselected observational cohort of patients. METHODS: During a two-year period, all patients over 18 years with acute stroke who were admitted within four-hours from onset of symptoms in 12 centers were registered. We compared outcomes in patients who were treated with alteplase with patients who were not treated with alteplase. The primary outcome was good functional outcome at three-months measured with the modified Rankin Scale ≤2). The safety end point was symptomatic intracranial hemorrhage and mortality. We used a multivariable logistic regression model to adjust for baseline imbalances and multilevel analysis to take into account within center correlations. RESULTS: Overall, 1657 patients with ischemic stroke were admitted within four-hours from onset of symptoms and 696 (42%) were treated with alteplase. Treatment with alteplase was associated with a favorable outcome (adjusted odds ratio 1·3; 95% confidence interval 1·0 to 1·7). After further adjustment for potential clustering effects, the adjusted odds ratio for good outcome was 1·4 (95% confidence interval 1·0 to 1·8). Thirty-six (5%) of the 696 patients treated with alteplase had a symptomatic intracranial bleeding complication. CONCLUSIONS: Thrombolysis for ischemic stroke with intravenous alteplase is an effective treatment also in an unselected observational cohort of patients.

Promoting thrombolysis in acute ischemic stroke.

BACKGROUND AND PURPOSE: Thrombolysis with intravenous recombinant tissue plasminogen activator is an effective treatment for acute ischemic stroke, but the number of treatable patients is limited. The PRomoting ACute Thrombolysis in Ischemic StrokE (PRACTISE) trial evaluated the effectiveness of a multidimensional implementation strategy for thrombolysis with intravenous recombinant tissue plasminogen activator in acute ischemic stroke. METHODS: The PRACTISE trial was a national multicenter cluster-randomized controlled trial with randomization after pairwise matching. Twelve hospitals, both urban and community, academic and nonacademic, in the Netherlands participated. All patients admitted with stroke within 24 hours from onset of symptoms were registered. The intervention included 5 implementation meetings based on the Breakthrough Series model. The primary outcome was treatment with thrombolysis. Secondary outcomes were admission within 4 hours after onset of symptoms, death or disability at 3 months, and quality of life. RESULTS: Overall 5515 patients were included in the study' 308 patients (12.2%) in the control centers and 393 patients (13.1%) in the intervention centers were treated with thrombolysis (adjusted OR, 1.25; 95% CI, 0.93 to 1.68). Among the 1657 patients with ischemic stroke admitted within 4 hours from onset, 391 (44.5%) of 880 in the intervention centers were treated with thrombolysis and 305 (39.3%) of 777 in the control centers; the adjusted OR for treatment with thrombolysis was 1.58 (95% CI, 1.11 to 2.27). CONCLUSIONS: An intensive implementation strategy increases the proportion of patients with acute stroke treated with thrombolysis in real-life settings. An apparently pivotal factor in the improvement of the treatment rate is better application of contraindications for thrombolysis.

Association between carotid plaque characteristics and cerebral white matter lesions: one-year follow-up study by MRI.

OBJECTIVE: To prospectively assess the relation between carotid plaque characteristics and the development of new cerebral white matter lesions (WMLs) at MRI. METHODS: Fifty TIA/stroke patients with ipsilateral 30-69% carotid stenosis underwent MRI of the plaque at baseline. Total plaque volume and markers of vulnerability to thromboembolism (lipid-rich necrotic core [LRNC] volume, fibrous cap [FC] status, and presence of intraplaque hemorrhage [IPH]) were assessed. All patients also underwent brain MRI at baseline and after one year. Ipsilateral cerebral WMLs were quantified with a semiautomatic method. RESULTS: Mean WML volume significantly increased over a one-year period (6.52 vs. 6.97 mm(3), P = 0.005). WML volume at baseline and WML progression did not significantly differ (P>0.05) between patients with 30-49% and patients with 50-69% stenosis. There was a significant correlation between total plaque volume and baseline ipsilateral WML volume (Spearman ρ = 0.393, P = 0.005). There was no significant correlation between total plaque volume and ipsilateral WML progression. There were no significant associations between LRNC volume and WML volume at baseline and WML progression. WML volume at baseline and WML progression did not significantly differ between patients with a thick and intact FC and patients with a thin and/or ruptured FC. WML volume at baseline and WML progression also did not significantly differ between patients with and without IPH. CONCLUSION: The results of this study indicate that carotid plaque burden is significantly associated with WML severity, but that there is no causal relationship between carotid plaque vulnerability and the occurrence of WMLs.

Carotid plaques in transient ischemic attack and stroke patients: one-year follow-up study by magnetic resonance imaging.

OBJECTIVE: To investigate the natural course of carotid plaque progression in transient ischemic attack/stroke patients by using serial multisequence magnetic resonance imaging (MRI). MATERIALS AND METHODS: Forty transient ischemic attack/stroke patients with ipsilateral <70% carotid stenosis underwent MRI of the plaque ipsilateral to the symptomatic side at baseline and after 1 year. The MRI protocol consisted of T1-weighted turbo field-echo, time-of-flight, T2-weighted turbo spin-echo (TSE), and pre- and postgadopentetate dimeglumine-enhanced T1-weighted TSE images. For each plaque, carotid lumen volume, wall volume, total vessel volume (=carotid lumen volume + wall volume), the presence of a lipid-rich necrotic core (LRNC), fibrous cap (FC) status, and the presence of intraplaque hemorrhage (IPH) were assessed at both time points. RESULTS: Over a 1-year period, mean carotid lumen volume decreased with 4.8% ± 2.0% (±standard error) (P = 0.013). Mean wall volume increased with 11.2% ± 2.2% (P < 0.001). Total vessel volume did not significantly change (P = 0.147). At baseline, there were 18 plaques with a LRNC, which also had a LRNC at 1-year follow-up. No plaque without a LRNC at baseline developed a LRNC during the follow-up period. All plaques with a LRNC had a thin and/or ruptured FC at both time points. Twelve patients had IPH both at baseline and at follow-up. In one patient, IPH disappeared, whereas in another patient, new IPH appeared at follow-up. The presence of IPH and a LRNC with a thin and/or ruptured FC were not significantly associated with plaque progression (P > 0.05). CONCLUSIONS: In symptomatic patients with an ipsilateral carotid plaque causing <70% stenosis, we found evidence for inward plaque remodeling over a 1-year period. Overall, the presence/absence of IPH, a LRNC, and FC status did not change over 1 year.

Searching for prognostic variables for secondary worsening after ischaemic stroke.

Secondary worsening of stroke symptoms is described in 13-37% of stroke patients, but the exact mechanism of this phenomenon remains unclear. The aim of this study is to find prognostic variables in correlation to secondary worsening of stroke symptoms in patients with lacunar or cortical strokes. In this prospective observational study we included all patients with ischaemic stroke; patients with transient ischaemic attack were excluded. Patients undergoing thrombolysis and becoming symptom-free after 24 h were still included in our analyses. Secondary worsening of stroke symptoms was defined as an increase of two or more points on the NIH Stroke Scale (NIHSS). The NIHSS score was assessed on admission, at discharge, and when patients had symptoms that indicated worsening of stroke. Applying univariate and multivariable analysis, we studied the relation between symptoms indicating secondary worsening of stroke and prognostic variables such as extreme nocturnal blood pressure falls (>20% of the average blood pressure), infection, diabetes mellitus, hypertension, smoking, dyslipidaemia, a history of cardiovascular or cerebrovascular disease and thrombolysis. This study included 202 patients with a mean age of 72 years, 48.8% were men and 43% had a lacunar stroke. Secondary worsening of stroke symptoms occurred in 13.5% of all patients, more often but not significantly (NS) after lacunar than cortical strokes (16.8 and 11.4%, respectively), and in patients with extreme nocturnal blood pressure falls versus without (15.6 and 11.8%, respectively (NS)). There was no significant relation between the analysed prognostic variables and secondary worsening of stroke symptoms. This study did not show significant correlation between several variables and secondary worsening of stroke symptoms in patients with recent ischaemic stroke.

Symptomatic patients with mild and moderate carotid stenosis: plaque features at MRI and association with cardiovascular risk factors and statin use.

BACKGROUND AND PURPOSE: The objectives of this study were to assess plaque characteristics in symptomatic patients with mild and moderate carotid stenosis and to explore associations with cardiovascular risk factors and statin use. METHODS: One hundred patients with transient ischemic attack or stroke with ipsilateral mild and moderate carotid stenosis underwent MR plaque imaging. RESULTS: Patients with moderate stenosis had plaques with a higher prevalence of intraplaque hemorrhage (48.7% versus 19.7%, P=0.002) and a thin and/or ruptured fibrous cap (61.5% versus 36.1%, P=0.013), and larger lipid-rich necrotic core percentage (12.3% versus 6.8%, P=0.042) and smaller fibrous tissue percentage (82.7% versus 88.4%, P=0.024). Increasing age was positively associated with intraplaque hemorrhage (OR [per year]=1.08; 95% CI, 1.02 to 1.14; P=0.011). Statin use was negatively associated with intraplaque hemorrhage (OR=0.30; 95% CI, 0.10 to 0.93; P=0.038), a thin and/or ruptured fibrous cap (OR=0.34; 95% CI, 0.13 to 0.89; P=0.028), and with lipid-rich necrotic core percentage (B=-7.91; 95% CI, -13.60 to -2.22; P=0.007). Statin use was positively associated with fibrous tissue percentage (B=7.77; 95% CI, 2.40 to 13.14; P=0.005). CONCLUSIONS: We found that symptomatic patients with moderate stenosis have a higher prevalence of complicated plaques than patients with mild stenosis. Exploratory analysis showed that increasing age was positively associated with intraplaque hemorrhage, whereas statin use was negatively associated with complicated plaque features.

Multimodality imaging of carotid artery plaques: 18F-fluoro-2-deoxyglucose positron emission tomography, computed tomography, and magnetic resonance imaging.

BACKGROUND AND PURPOSE: This study's objective was to compare (18)F-fluoro-2-deoxyglucose positron emission tomography ((18)F-FDG PET), CT, and MRI of carotid plaque assessment. MATERIALS AND METHODS: Fifty patients with symptomatic carotid atherosclerosis underwent (18)F-FDG PET/CT and MRI. Correlations and agreement between imaging findings were assessed by Spearman and Pearson rank correlation tests, t tests, and Bland-Altman plots. RESULTS: Spearman rho between plaque (18)F-FDG standard uptake values and CT/MRI findings varied from -0.088 to 0.385. Maximum standard uptake value was significantly larger in plaques with intraplaque hemorrhage (1.56 vs 1.47; P=0.032). Standard uptake values did not significantly differ between plaques with an intact and thick fibrous cap and plaques with a thin or ruptured fibrous cap on MRI. (1.21 vs 1.23; P=0.323; and 1.45 vs 1.54; P=0.727). Pearson rho between CT and MRI measurements varied from 0.554 to 0.794 (P<0.001). For lipid-rich necrotic core volume, the CT-MRI correlation was stronger in mildly (10%) calcified plaques (Pearson rho 0.730 vs 0.475). Mean difference in measurement +/-95% limits of agreement between CT and MRI for minimum lumen area, volumes of vessel wall, lipid-rich necrotic core, calcifications, and fibrous tissue were 0.4+/-18.1 mm(2) (P=0.744), -41.9 +/-761.7 mm(3) (P=0.450), 78.4+/-305.0 mm(3) (P<0.001), 180.5+/-625.7 mm(3) (P=0.001), and -296.0+/-415.8 mm(3) (P<0.001), respectively. CONCLUSIONS: Overall, correlations between (18)F-FDG PET and CT/MRI findings are weak. Correlations between CT and MRI measurements are moderate to strong, but there is considerable variation in absolute differences.

Reproducibility of fibrous cap status assessment of carotid artery plaques by contrast-enhanced MRI.

BACKGROUND AND PURPOSE: Reproducibility in identifying the fibrous cap (FC) of carotid artery plaques by noncontrast-enhanced MRI has been shown to be poor. The objective of this study was to assess the reproducibility of multisequence MRI, including contrast-enhanced images, in assessing FC status. METHODS: Forty-five symptomatic patients with 30% to 69% carotid artery stenosis underwent a multisequence MRI protocol, which included contrast-enhanced images. FC status (ie, discrimination between fibrotic and/or calcified plaques, plaques with a lipid-rich necrotic core and an intact and thick FC, and plaques with a lipid-rich necrotic core and a thin and/or ruptured FC) was independently assessed by 3 observers of which one also scored all images on a different occasion. Linear weighted kappa coefficients (kappa) were calculated as indicators of inter- and intraobserver agreement. RESULTS: On a per-slice basis, interobserver agreement was good (kappa=0.60, 0.64, and 0.71), whereas intraobserver agreement was very good (kappa=0.86). On a per-plaque basis, interobserver agreement was good (kappa=0.64, 0.69, and 0.78), whereas intraobserver agreement was very good (kappa=0.96). CONCLUSIONS: This study found good interobserver and very good intraobserver agreement in assessing FC status of carotid artery plaques. Future studies are warranted to determine the predictive value of FC status assessment by multisequence MRI, including contrast-enhanced images, on the occurrence of (recurrent) cerebral ischemic events.

Stroke-associated infection is an independent risk factor for poor outcome after acute ischemic stroke: data from the Netherlands Stroke Survey.

BACKGROUND: Infections are a common and serious threat to patients with acute ischemic stroke. The aim of this study was to assess the effect of infection on mortality and functional outcome at discharge and at 1 year. METHODS: From a consecutive cohort study in 11 centers, the Netherlands Stroke Survey, we selected 521 patients with ischemic stroke admitted to hospital within 48 h of onset. Stroke-associated infection was defined as infection occurring within 7 days after admission. Poor outcome (modified Rankin score >2) was recorded at discharge and at 1 year. RESULTS: Stroke-associated infection occurred in 78 patients (15%); 39 of these (7.5%) had pneumonia and 23 (4.4%) had urinary tract infection. Overall, 276 patients (53%) had a poor outcome at 1 year. Poor outcome was recorded in 69 patients with stroke-associated infection (88%), and 37 of the 78 patients with stroke-associated infection (47%) had died at 1 year. After adjustment for confounders, stroke-associated infection was associated with poor outcome at discharge [odds ratio (OR) 2.6, 95% confidence interval (CI) 1.0-6.7] and at 1 year (OR 3.8, 95% CI 1.8-8.9). Pneumonia had a stronger association with poor outcome at 1 year (OR 10, 95% CI 2.2-46). CONCLUSIONS: This study suggests that stroke-associated infection, in particular pneumonia, is independently associated with poor functional outcome after ischemic stroke.

Intravenous thrombolysis in acute ischaemic stroke: from trial exclusion criteria to clinical contraindications. An international Delphi study.

OBJECTIVE: Several studies indicate that only a small proportion of patients with acute ischaemic stroke are treated with intravenous thrombolysis. Indications and contraindications for this treatment are usually based on the inclusion and exclusion criteria of randomised clinical trials. The trial context of these criteria hampers implementation in real life settings. We therefore aimed to obtain specialist opinion in a Delphi consensus on these contraindications. METHODS: We used the Delphi approach on an international group of specialists in the field of thrombolysis. Inclusion and exclusion criteria were reworded into 18 quantitatively phrased propositions. Feedback consisted of the median score, interquartile range and the panellist's own score in the previous round. For each item, we defined consensus as the achievement of an interdecile range within two prespecified clinically relevant units. RESULTS: Thirty-one specialists participated in the first round and 30 completed all three rounds. Consensus was reached on 12 of the 18 propositions: previous ischaemic stroke, head trauma and gastrointestinal tract bleeding should not have taken place earlier than 1.5 months, 2 months and 14 days, respectively; the severity of the neurological deficit is defined as a National Institutes of Health Stroke Scale (NIHSS) score of 2-3 or more, and blood pressure level should not be >185/110 mmHg; platelet count should be >90x10(12)/l, glucose levels 2.7-22 mmol/l, international normalised ratio <1.5 and activated partial thromboplastin time <50 s. No consensus was reached on propositions concerning the stroke onset to treatment time, patient's age, recent medical procedures, spontaneous improvement rate and blood pressure treatment. CONCLUSIONS: We present specialists' opinion on contraindications for intravenous thrombolysis in ischaemic stroke. The results of this study may be relevant for routine clinical practice as they may help to increase the number of treated patients.

Promoting Acute Thrombolysis for Ischaemic Stroke (PRACTISE).

RATIONALE: Thrombolysis with intravenous rtPA is an effective treatment for patients with ischaemic stroke if given within 3 h from onset. Generally, more than 20% of stroke patients arrive in time to be treated with thrombolysis. Nevertheless, in most hospitals, only 1-8% of all stroke patients are actually treated. Interorganisational, intraorganisational, medical and psychological barriers are hampering broad implementation of thrombolysis for acute ischaemic stroke. AIMS: To evaluate the effect of a high-intensity implementation strategy for intravenous thrombolysis in acute ischaemic stroke, compared with regular implementation; to identify success factors and obstacles for implementation and to assess its cost-effectiveness, taking into account the costs of implementation. DESIGN: The PRACTISE study is a national cluster-randomised-controlled trial. Twelve hospitals have been assigned to the regular or high-intensity intervention by random allocation after pair-wise matching. The high-intensity implementation consists of training sessions in conformity with the Breakthrough model, and a tool kit. All patients who are admitted with acute stroke and onset of symptoms not longer than 24 h are registered. STUDY OUTCOMES: The primary outcome measure is treatment with thrombolysis. Secondary outcomes are admission within 4 h after onset of symptoms, death or disability at 3 months, the rate of haemorrhagic complications in patients treated with thrombolysis, and costs of implementation and stroke care in the acute setting. Tertiary outcomes are derived from detailed criteria for the organisational characteristics, such as door-to-needle time and protocol violations. These can be used to monitor the implementation process and study the effectiveness of specific interventions. DISCUSSION: This study will provide important information on the effectiveness and cost-effectiveness of actively implementing an established treatment for acute ischaemic stroke. The multifaceted aspect of the intervention will make it difficult to attribute a difference in the primary outcome measure to a specific aspect of the intervention. However, careful monitoring of intermediate parameters as well as monitoring of accomplished SMART tasks can be expected to provide useful insights into the nature and role of factors associated with implementation of thrombolysis for acute ischaemic stroke, and of effective acute interventions in general.

Quality of hospital and outpatient care after stroke or transient ischemic attack: insights from a stroke survey in the Netherlands.

BACKGROUND AND PURPOSE: Limited data are available on management of outpatients with stroke or transient ischemic attack (TIA) and on clinicians' reasons for withholding procedures recommended by guidelines. We assessed to what extent guidelines are appropriately applied after ischemic stroke or TIA, in admitted patients as well as outpatients. METHODS: A survey was conducted in 11 centers in the Netherlands, which prospectively enrolled 579 admitted patients and 393 outpatients. Data were collected by trained research assistants. Duplicate assessment in 10% of patients showed good agreement with neurologists (median kappa=0.86). Treating neurologists were asked to provide arguments for withholding recommended procedures in eligible patients. RESULTS: Recommended acute procedures were provided in the majority of admitted patients, but less often in outpatients: brain imaging (98% and 93%, respectively), 12-lead ECG (96% and 81%), laboratory tests (97% and 86%), aspirin within 48 hours (90% and 68% of eligible patients). Secondary preventive measures were not always taken in both eligible inpatients and eligible outpatients: carotid endarterectomy (provided in 31% and 30% of patients), antiplatelet agents (93% and 90%), oral anticoagulants (60% and 48%), antihypertensive agents (57% and 44%), and cholesterol-lowering therapy (71% and 52%). Reasons for withholding recommended procedures were plausible for almost all admitted patients, but were unclear in the majority of outpatients. CONCLUSIONS: Compared with other national stroke surveys, we found high-quality acute care in admitted ischemic stroke patients, whereas secondary prevention was comparably poor. Although the majority of our centers have rapid-access TIA clinics, there is still substantial potential to improve quality of stroke care in outpatients.

Direction of flow in posterior communicating artery on magnetic resonance angiography in patients with occipital lobe infarcts.

BACKGROUND AND PURPOSE: In some people the blood supply to the posterior cerebral artery occurs partly or even exclusively via the carotid system. This anatomic configuration may influence the risk of occipital lobe infarction. We studied the presence and direction of flow in the posterior communicating artery (PCoA) in patients with an occipital lobe infarct and in healthy controls. METHODS: Forty-seven patients with an occipital lobe infarct were studied by MR angiography, as well as 50 young healthy controls. Special attention was paid to the presence of a PCoA and, if present, to the direction of flow. RESULTS: Significantly fewer patients than controls had an exclusive blood supply to the posterior cerebral artery via the carotid system, in both the affected (4% versus 17%; 95% CI of difference, 4% to 22%) and unaffected hemispheres (5% versus 17%; 95% CI of difference, 3% to 22%). Patients also less often had a patent PCoA with anteroposterior flow than controls (affected hemisphere, 8% versus 22%; unaffected hemisphere, 12% versus 22%; 95% CI of differences, 3% to 25% and -2% to 23%, respectively). With analysis at the level of individuals, significantly more patients showed no anteroposterior flow through the PCoA in either hemisphere than controls (79% versus 42%; 95% CI of difference, 19% to 55%). CONCLUSIONS: Supply of the posterior cerebral artery by the carotid system occurs less often in patients with an occipital lobe infarct than in healthy controls. The same was true for the unaffected hemisphere of patients, which suggests that the anatomic difference represents a causal factor (fewer collateral pathways after occlusion of the posterior cerebral artery or its branches) rather than a consequence (redistribution of blood flow after occipital infarction).

Blood supply of the posterior cerebral artery by the carotid system on angiograms.

BACKGROUND AND PURPOSE: Occipital lobe infarcts are traditionally attributed to vertebrobasilar disease. However, anatomical studies indicate that in some people the supply of the posterior cerebral artery is via the carotid system. We investigated how often such a developmental variant in the cerebral blood supply was present during life. METHODS: We retrospectively studied 212 conventional four-vessel cerebral angiograms. Eighteen subjects were excluded beforehand, because of vascular abnormalities causing important hemodynamic changes. We determined whether a fetal variant was present, and in other cases whether there was a functioning posterior communicating artery. RESULTS: In 11 % of hemispheres the posterior cerebral artery was exclusively supplied by the internal carotid artery; in a further 46 % of hemispheres the internal carotid artery might contribute, via a patent posterior communicating artery. In 75 % of subjects the internal carotid artery contributed in at least one hemisphere to the blood flow of the posterior cerebral artery. CONCLUSIONS: The implication of our findings is that an occipital lobe infarct can be caused by ipsilateral carotid disease in a proportion of cases between 10 and 60 %. This implies that carotid endarterectomy might be beneficial in some patients with severe carotid stenosis and infarction in the territory of the posterior cerebral artery.