01OverviewDefinition, clinical context and the essential points that orientate the chapter.
Asymptomatic carotid stenosis is extracranial carotid atherosclerosis without a recent ipsilateral retinal or cerebral ischaemic event attributable to that artery. Remote events and contralateral symptoms require careful classification, while non-focal dizziness or syncope usually does not make a carotid plaque symptomatic. The distinction matters because the immediate stroke risk and the absolute benefit from intervention are much lower than after a recent ipsilateral TIA or stroke.
Modern medical treatment has reduced ipsilateral stroke rates compared with the eras of the original asymptomatic CEA trials. Every patient needs cardiovascular risk assessment and prevention, but only a minority should be considered for revascularisation. Selection integrates 60–99% severity, imaging or clinical features associated with higher stroke risk on best medical treatment, life expectancy beyond about five years, patient preference and a centre's audited 30-day stroke or death risk below 3%.
Routine population screening is not recommended because severe disease is uncommon and false-positive or incidental findings can lead to anxiety, repeated imaging and harmful procedures. Selective assessment may be considered in some people with multiple vascular risk factors when finding disease would improve prevention and the person would realistically consider intervention. A bruit alone is neither a reliable grade nor an automatic indication for scanning.
Key points
- New focal neurological symptoms are no longer asymptomatic disease: activate the TIA or stroke pathway immediately and reassess carotid causality.
- Do not offer routine population screening for asymptomatic carotid stenosis; low prevalence, false positives and downstream procedural harm undermine net benefit.
- Most asymptomatic stenosis receives best medical treatment: smoking cessation, exercise and diet support, blood-pressure and diabetes control, and intensive lipid lowering.
- Do not offer routine revascularisation when life expectancy is under five years or high-risk plaque or clinical features are absent.
- Selected 60–99% stenosis may merit MDT discussion only when stroke risk on medical treatment appears higher, life expectancy is adequate and audited 30-day stroke/death risk is below 3%.
- Confirm treatment-determining duplex disease with CTA, MRA or a second expert duplex and use NASCET-equivalent grading.
- Long-term aspirin plus clopidogrel is not routine for asymptomatic stenosis; choose antiplatelet treatment by guideline and individual bleeding and cardiovascular context.
- Surveillance is useful only when progression or new high-risk features would alter management; define the interval and intended action before ordering repeats.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Systemic atherosclerosis
Age, smoking, hypertension, dyslipidaemia, diabetes and chronic kidney disease promote carotid plaque, often alongside coronary, aortic and peripheral arterial disease.
Local plaque evolution
Lesions cluster at the carotid bifurcation where disturbed flow favours lipid deposition, inflammation, calcification and remodelling over many years without necessarily causing symptoms.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Luminal narrowing
Progressive plaque reduces the internal carotid lumen and raises local velocity, although collateral cerebral circulation often preserves perfusion until disease becomes very severe.
- 2Silent embolisation
Plaque surface disruption can release small emboli that cause no recognised deficit or leave silent ipsilateral infarcts, which may signal higher future risk.
- 3Risk under treatment
Smoking cessation, blood-pressure control and lipid lowering stabilise plaque and reduce systemic events, lowering contemporary ipsilateral stroke rates compared with historical untreated cohorts.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
Plaque found during imaging without a relevant ipsilateral event is asymptomatic and should enter prevention and selection assessment.
A cervical bruit suggests turbulent flow but neither proves severe ICA stenosis nor excludes it when absent.
Progression, silent ipsilateral infarction, microembolic signals, impaired cerebrovascular reserve or adverse plaque morphology may increase concern on medical treatment.
Amaurosis fugax or retinal artery occlusion ipsilateral to the lesion makes urgent symptomatic assessment necessary.
Contralateral weakness, sensory loss, aphasia or neglect demands immediate TIA or stroke assessment and reclassification.
Frailty, advanced comorbidity or life expectancy under five years makes delayed preventive surgical benefit unlikely to exceed early harm.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Carotid duplex ultrasoundFirst step - Why
- Grade stenosis and establish a surveillance baseline
- Interpretation and limitations
- Use a validated NASCET-equivalent category with plaque and waveform context; a high-grade treatment-determining result requires corroboration.
- 02
CTA or MRA - Why
- Confirm severity and define procedural anatomy when intervention is considered
- Interpretation and limitations
- Cross-sectional imaging assesses lumen and arch or intracranial anatomy, with modality selected around renal, contrast, radiation and device constraints.
- 03
Brain CT or MRI - Why
- Identify silent infarction or alternative neurological pathology
- Interpretation and limitations
- An ipsilateral silent embolic infarct can contribute to higher-risk selection but does not replace clinical symptom history or mandate intervention.
- 04
Full cardiovascular assessment - Why
- Measure modifiable systemic vascular risk and treatment safety
- Interpretation and limitations
- Blood pressure, smoking, lipids, HbA1c, renal and liver function direct prevention; carotid disease marks coronary and peripheral risk too.
- 05
Specialist plaque-risk tests - Why
- Refine risk in selected intervention discussions
- Interpretation and limitations
- Transcranial microemboli, plaque MRI or cerebrovascular reserve may support higher-risk classification where available, but none is a universal screening test.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Symptomatic carotid stenosis
A recent attributable ipsilateral retinal or hemispheric event places the patient in an urgent secondary-prevention pathway with a larger potential benefit from early CEA.
Carotid near-occlusion
Extreme stenosis with distal ICA collapse behaves differently from ordinary high-grade disease and requires expert cross-sectional imaging rather than routine percentage-based selection.
Non-atherosclerotic disease
Dissection, carotid web, fibromuscular dysplasia and radiation arteriopathy have different morphology, populations and management and should not inherit asymptomatic atherosclerosis rules.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01ManagementIncidental asymptomatic stenosisFirst stepA carotid lesion is found without recent attributable ipsilateral retinal or cerebral symptoms+
- 1Verify symptom history, side, duplex quality and NASCET-equivalent severity before calling the disease asymptomatic.
- 2Assess smoking, blood pressure, diabetes, lipids, kidney disease and other vascular beds, then start or optimise prevention.
- 3Explain that contemporary stroke risk is often low on medical treatment and that a procedure has an immediate stroke or death risk.
- 4If surveillance is appropriate, define its purpose, interval and the progression or new feature that would trigger MDT review.
- 5Tell the patient to seek emergency help for new focal weakness, speech disturbance or monocular visual loss.
02SelectionPossible preventive interventionConfirmed 60–99% stenosis has higher-risk features despite best medical treatment and adequate longevity+
- 1Corroborate the duplex grade with CTA, MRA or a second expert duplex and review relevant brain and plaque features.
- 2Estimate life expectancy, frailty, anatomy and comorbidity and confirm the service's audited 30-day stroke or death rate is below 3%.
- 3Discuss CEA as the established reference intervention, with CAS reserved for selected anatomy or surgical-risk contexts after MDT review.
- 4Use shared decision-making to compare the modest delayed stroke reduction with immediate stroke, death, myocardial, nerve and bleeding harms.
- 5Continue medical prevention whether intervention is accepted, declined or judged inappropriate.
03ReclassificationNew focal symptomsThe patient develops ipsilateral retinal or cerebral ischaemic symptoms during surveillance+
- 1Activate immediate stroke or TIA assessment and treat any persistent deficit as a hyperacute stroke emergency.
- 2Start guideline-directed acute antithrombotic treatment after haemorrhage and reperfusion considerations are addressed.
- 3Repeat brain and carotid imaging promptly because current anatomy and infarct burden determine the urgent symptomatic pathway.
- 4Refer stable non-disabling cases with 50–99% NASCET stenosis urgently for time-sensitive CEA assessment.
Key medicines and prescribing safety2 treatments · regimens, roles and cautions+
Atorvastatin
For established cardiovascular disease, offer atorvastatin 80 mg orally once daily unless interactions, adverse-effect risk or preference justify a lower dose; measure lipid response and liver transaminases after 2–3 months.Review pregnancy, active liver disease, interacting medicines, heavy alcohol use and prior muscle toxicity. Use the maximum tolerated intensity when 80 mg is unsuitable; check creatine kinase for unexplained muscle symptoms, transaminases at 12 months, and annual lipids for secondary prevention.
Clopidogrel
When antiplatelet therapy is selected and aspirin is unsuitable, use the verified product dose of 75 mg orally once daily, with duration reviewed against the patient's vascular indication and bleeding risk.Avoid with active pathological bleeding or severe hepatic impairment. Review occult bleeding, blood counts when symptoms suggest dyscrasia, oral anticoagulants, NSAIDs and other bleeding drugs. Avoid routine omeprazole or esomeprazole because CYP2C19 inhibition may reduce clopidogrel activation; renal experience is limited.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Ipsilateral TIA or stroke
Plaque embolisation may cause sudden monocular blindness or contralateral neurological deficit, converting the lesion to symptomatic disease and increasing immediate recurrence risk.
Systemic vascular events
The same atherosclerotic burden increases myocardial infarction, vascular death and limb-event risk, sometimes exceeding the risk from the carotid territory itself.
Intervention-related harm
Preventive CEA or CAS can cause stroke, death, myocardial infarction, cranial nerve injury or bleeding before any delayed stroke-prevention benefit accrues.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Ask at every review about interval monocular visual loss, weakness, sensory change or speech disturbance; new focal symptoms require emergency reclassification.
- Measure adherence, smoking status, blood pressure, diabetes control and lipid response rather than treating serial lumen percentage as the only outcome.
- Use the same validated duplex laboratory for surveillance where possible and confirm apparent rapid progression before changing management.
- Review life expectancy, frailty and willingness for intervention before each scan; stop surveillance when its result would no longer alter care.
- For statin therapy check full lipids and liver transaminases at 2–3 months, transaminases at 12 months and an annual lipid profile for secondary prevention.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Asymptomatic is a history diagnosis
The scan cannot determine symptom status. Ask specifically about prior monocular visual loss, aphasia and contralateral deficits, with dates and side.
Medical risk is systemic
Carotid plaque predicts myocardial and peripheral vascular events as well as stroke, so prevention should address the whole vascular patient.
Old trials need context
The landmark CEA trials predated current statin intensity and risk-factor control, so their absolute benefit cannot be transferred uncritically to every modern patient.
Procedural threshold is strict
Because baseline ipsilateral stroke risk is low, asymptomatic intervention requires a lower audited perioperative stroke or death risk than symptomatic intervention.
Surveillance needs an action
Repeating duplex without a defined threshold for specialist review creates anxiety and workload without improving outcomes, especially when the patient would not choose intervention.
11Common pitfallsFrequent interpretation and management errors.
- 01
Calling dizziness, syncope or imbalance a carotid symptom without a focal retinal or hemispheric syndrome.
- 02
Screening healthy adults routinely and creating a cascade from false-positive duplex findings to invasive treatment.
- 03
Offering CEA from stenosis percentage alone without higher-risk features, adequate longevity or audited procedural outcomes.
- 04
Stopping cardiovascular prevention because the plaque has never caused a neurological symptom.
- 05
Prescribing indefinite aspirin plus clopidogrel for asymptomatic disease without another evidence-based indication.
- 06
Continuing annual surveillance after frailty or patient preference means that no result would change management.