Atherosclerotic narrowing of the cervical internal carotid artery; major modifiable cause of ischemic stroke and TIA.
Also known as: carotid stenosis, extracranial carotid disease, internal carotid artery stenosis, ICA stenosis
Overview
Narrowing of the extracranial internal carotid artery, most often at the carotid bifurcation, due to atherosclerotic plaque. Severity is graded by percent diameter reduction (NASCET method): <50% mild, 50-69% moderate, 70-99% severe, 100% occluded. Symptomatic stenosis = ipsilateral retinal or hemispheric ischemic event (TIA, stroke, amaurosis fugax) within 6 months.
Epidemiology
Moderate-to-severe (≥50%) stenosis in ~2% of adults under 70 and up to 8% over 70. Higher in men, smokers, diabetics, hypertensives. Accounts for ~10-15% of ischemic strokes.
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Question 1NeurologyMedium
A 71-year-old man with hypertension, hyperlipidemia, and a 40-pack-year smoking history presents after a 10-minute episode of painless vision loss in his right eye, which he describes as a gray curtain descending over the eye that then lifted completely. He has no headache, neck pain, or limb weakness. Vital signs are normal and the rhythm is regular. Funduscopy of the right eye reveals a bright refractile plaque at a retinal artery branch point, and a soft bruit is heard over the right neck. ECG shows normal sinus rhythm. Which of the following is the most likely underlying cause of this patient's vision loss?
ACardiogenic cerebral embolism
BCarotid artery atherosclerosis
CSpontaneous carotid dissection
DVertebrobasilar atherosclerosis
Reveal answer & full explanation
Correct answer: B — Carotid artery atherosclerosis
ACardiogenic cerebral embolism
BCarotid artery atherosclerosis✓
CSpontaneous carotid dissection
DVertebrobasilar atherosclerosis
Why Carotid artery atherosclerosis is correct
Transient monocular vision loss described as a descending curtain is amaurosis fugax, the classic ocular TIA of carotid embolic disease, and counts as a symptomatic ipsilateral ischemic event.
The Hollenhorst plaque on funduscopy is a cholesterol embolus lodged in a retinal arteriole, pointing to artery-to-artery embolism from atherosclerotic plaque at the ipsilateral carotid bifurcation.
The risk-factor profile (older man, hypertension, hyperlipidemia, heavy smoking) and the right-sided carotid bruit fit an atherosclerotic carotid source; the next step is urgent carotid duplex ultrasonography to grade the stenosis.
Why the others are wrong
Cardiogenic cerebral embolism comes from the heart (atrial fibrillation, valve disease, LV thrombus), usually strikes multiple vascular territories with hemispheric deficits; the regular rhythm, normal sinus ECG, and isolated retinal cholesterol embolus argue against a cardiac source.
Spontaneous carotid dissection typically occurs in younger patients with neck pain, headache, or Horner syndrome after trauma or manipulation; this older smoker has none of those features, and a Hollenhorst plaque indicates atherosclerotic embolism rather than an intimal flap.
Vertebrobasilar atherosclerosis produces posterior-circulation symptoms such as vertigo, diplopia, dysarthria, or ataxia rather than monocular curtain vision loss, which is an anterior (carotid/retinal) circulation event.
Question 2NeurologyMedium
A 71-year-old man with hypertension, hyperlipidemia, and a 40-pack-year smoking history reports three episodes over the past week of painless vision loss in his right eye, each described as a gray curtain descending over the eye and resolving within 5 minutes. Neurologic exam is normal. Funduscopy shows a bright refractile plaque at a retinal arteriole branch point. Carotid duplex ultrasonography demonstrates 80% stenosis of the right internal carotid artery at the bifurcation. Which of the following best explains the mechanism of this patient's transient vision loss?
AIntramural hematoma from a carotid arterial intimal tear
BEmbolism from a left atrial appendage mural thrombus
COcclusion of a lipohyalinotic deep penetrating arteriole
DEmbolism from a ruptured carotid atheromatous plaque
Reveal answer & full explanation
Correct answer: D — Embolism from a ruptured carotid atheromatous plaque
AIntramural hematoma from a carotid arterial intimal tear
BEmbolism from a left atrial appendage mural thrombus
COcclusion of a lipohyalinotic deep penetrating arteriole
DEmbolism from a ruptured carotid atheromatous plaque✓
Why Embolism from a ruptured carotid atheromatous plaque is correct
Atherosclerotic plaque forms preferentially at the carotid bifurcation because of disturbed, turbulent flow; when the fibrous cap ruptures it exposes thrombogenic material that sheds emboli downstream.
These artery-to-artery emboli travel to the ipsilateral retina via the ophthalmic artery, producing amaurosis fugax — the transient monocular "curtain" vision loss described — and can also reach the ipsilateral hemisphere to cause TIA or stroke.
The refractile retinal plaque (a Hollenhorst cholesterol embolus) is the visible signature of this embolic mechanism, and the 80% ipsilateral internal carotid stenosis localizes the embolic source.
Why the others are wrong
Embolism from a left atrial appendage mural thrombus is cardioembolism, typically from atrial fibrillation; it scatters emboli to multiple vascular territories rather than producing repeated, stereotyped events confined to one eye ipsilateral to a high-grade carotid lesion.
Occlusion of a lipohyalinotic deep penetrating arteriole is the mechanism of small-vessel (lacunar) stroke, producing deep syndromes such as pure motor or pure sensory deficits, not transient monocular vision loss arising from a large extracranial artery.
Intramural hematoma from a carotid arterial intimal tear describes carotid dissection, which classically occurs in younger patients with neck pain, Horner syndrome, or recent trauma or neck manipulation, not in an older smoker with bifurcation atherosclerotic stenosis.
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Atherosclerotic plaque develops preferentially at the carotid bifurcation due to disturbed flow patterns. Plaque progression narrows the lumen and may rupture, exposing thrombogenic material and producing embolization (artery-to-artery emboli to the ipsilateral hemisphere or retina). Hemodynamic compromise contributes when stenosis is critical (>70%) or collateral supply is poor.
Clinical presentation
Symptoms
Many cases asymptomatic — found on screening or workup of bruit/CAD
Transient ischemic attack — unilateral weakness, sensory loss, aphasia (dominant hemisphere), or visual field cut lasting <24 h
Amaurosis fugax — transient monocular vision loss ('curtain' descending), classic for carotid embolic disease
Ischemic stroke with persistent deficit in the ipsilateral hemisphere
Signs / physical exam
Carotid bruit on auscultation (insensitive and nonspecific — may be absent in severe stenosis or present in non-flow-limiting plaque)
Hollenhorst plaque on funduscopy (cholesterol embolus in retinal artery)
Focal neurologic deficit during or after ischemic event
Evidence of systemic atherosclerosis: diminished peripheral pulses, abdominal bruits, xanthomas
Classic findings
Older smoker with transient monocular vision loss or contralateral weakness — high suspicion for symptomatic carotid stenosis.
Carotid artery dissection — Young patient, neck pain, Horner syndrome, history of trauma or chiropractic manipulation; intimal flap or string sign on imaging
Fibromuscular dysplasia — Young to middle-aged women; 'string of beads' on imaging
flowchart TD
A[TIA, minor stroke,<br/>or amaurosis fugax] --> B[Carotid duplex<br/>ultrasound]
B --> C[CTA or MRA neck<br/>to confirm % stenosis]
C --> D{Symptomatic<br/>stenosis %}
D -->|70-99%| E[CEA within 2 weeks<br/>or CAS if high-risk anatomy]
D -->|50-69%| F[Individualized:<br/>consider CEA]
D -->|<50%| G[Medical therapy<br/>alone]
A2[Asymptomatic<br/>incidental finding] --> B
D2[Asymptomatic<br/>70-99%] --> H[Intensive medical<br/>therapy primary;<br/>CEA/CAS selected cases]
E --> I[Lifelong antiplatelet,<br/>statin, BP control,<br/>smoking cessation]
F --> I
G --> I
H --> I
Diagnostic and treatment algorithm for symptomatic and asymptomatic carotid artery stenosis.
Treatment
First-line
Aggressive medical therapy for ALL patients regardless of revascularization plan:
Antiplatelet — aspirin 81 mg daily; clopidogrel if ASA-intolerant; DAPT (aspirin + clopidogrel) for 21-90 days post stroke/TIA per CHANCE/POINT trial protocols
Smoking cessation — single most impactful modifiable factor
Lifestyle: Mediterranean diet, exercise, weight loss
Symptomatic stenosis 70-99%
Carotid endarterectomy (CEA) within 2 weeks of index event (greatest benefit) — strong indication (NASCET, ECST trials)
Surgeon-specific perioperative stroke/death rate must be <6%
Carotid artery stenting (CAS) — alternative when CEA high-risk anatomy (hostile neck, prior radiation, contralateral occlusion); younger age (<70) favors CAS while older age favors CEA (CREST: outcomes equivalent around age 70)
Hemodynamic instability with intervention (bradycardia, hypotension during CAS or CEA carotid sinus manipulation)
Death (most often from coexisting CAD)
PANCE pearls
Carotid bruit is neither sensitive nor specific — its absence does not exclude severe stenosis.
Amaurosis fugax is a TIA — workup urgently with carotid imaging; do not dismiss as 'just an eye problem.'
Symptomatic 70-99% stenosis: CEA within 2 weeks of the index event gives the maximal absolute risk reduction; do not delay for 'cooling off.'
Asymptomatic stenosis — modern medical therapy markedly reduced stroke risk; routine revascularization is no longer reflexive (await CREST-2).
Hyperperfusion syndrome after revascularization: severe ipsilateral headache, seizures, hemorrhage from sudden restoration of flow — control BP aggressively.
Patients with carotid disease die more often from MI than stroke — optimize cardiac risk.
References
NASCET — North American Symptomatic Carotid Endarterectomy Trial Collaborators. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. NEJM 1991;325:445-453.
ACAS — Executive Committee for the Asymptomatic Carotid Atherosclerosis Study. Endarterectomy for asymptomatic carotid artery stenosis. JAMA 1995;273:1421-1428.
CREST — Brott TG et al. Stenting versus endarterectomy for treatment of carotid-artery stenosis. NEJM 2010;363:11-23.
AHA/ASA 2021 — Kleindorfer DO et al. 2021 Guideline for the Prevention of Stroke in Patients With Stroke and Transient Ischemic Attack. Stroke 2021;52:e364-e467.
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