Carotid Artery Disease

Overview

Carotid artery disease refers to atherosclerotic narrowing of the carotid artery lumen. It is associated with approximately 10-15% of all ischaemic strokes. Stroke is the third leading cause of death and a principal cause of long-term disability in much of the industrialised world. The degree of internal carotid artery stenosis is the most important predictor of cerebral infraction among patients with extracranial carotid artery disease.¹

Anatomy

Common Carotid

Origin:

• Left common carotid: Aortic Arch
• Right common carotid: Brachiocephalic trunk of Aortic Arch

Common carotid arteries bifurcate variably at the C3/4 or C4/5 and give rise to internal carotid and external carotid.

External Carotid

Branches (from proximal to distal) – Some Anatomists Like Freaking Out Poor Medical Students:

• Superior Thyroid
• Ascending Pharyngeal
• Lingual
• Facial
• Occipital
• Posterior Auricular
• Maxillary
• Superficial Temporal

Internal Carotid

Important branches:

• Superior and Inferior Hypophyseal arteries – supply the pituitary gland
• Ophthalmic artery – supplies the eye
• Posterior Communicating – connects Internal Carotid and Posterior Cerebral

Terminates into: Anterior Cerebral and Middle Cerebral.

Carotid Sheath

Condensation of the deep cervical fascia that surrounds the great vessels of the neck

Contains:

• Internal Jugular vein
• Vagus nerve
• Common Carotid or Internal Carotid (depending on vertebral level observed)

Carotid body – cluster of chemoreceptor cells located at the bifurcation

Carotid sinus – dilation at the bifurcation and proximal aspect of internal carotid that contains baroreceptors.

Aetiology and Risk factors

• Advancing age
• Male gender
• Smoking
• Family history
• Atherosclerosis
• Hypertension
• Hypercholesterolaemia
• Other vascular aneurysm

Pathophysiology

The pathophysiology of cerebrovascular disease (stroke or TIA) can be of:

• Intracranial origin
• Extracranial origin
  • Flow-restrictive lesions – carotid artery stenosis most common
  • Embolism

Carotid Artery Stenosis pathophysiology

• Atherosclerosis formation in carotid artery at areas of turbulent flow (carotid bifurcation)
• Plaque instability and rupture create thromboembolic debris and lead to neurological injury
• Plaque ulceration and thrombosis are associated with neurological symptoms, independent of degree of stenosis

During periods prone to ischaemia, collateral flow is critical for cerebral blood flow compensation and a major determinant of the severity of the ischaemic insult

Other factors include: plaque morphology, duration of hypoperfusion, characteristics of the embolus, and cerebral vasoreactivity.

Another mechanism for infarction with carotid stenosis is a sudden drop in systemic blood pressure leading to ACA-MCA watershed territory stroke

Classification

Based on symptomatic status

• Symptomatic: associated with focal neurological symptoms such as stroke, TIA, or amaurosis fugax in the last 6 months
• Asymptomatic: not associated with neurological symptoms in the last 6 months

Based on degree of stenosis:

• Mild (<50% diameter reduction)
• Moderate (50% to 69% diameter reduction)
• Severe (70% to 99% diameter reduction)
• Near occlusion (very tight and long stenosis from carotid bifurcation to the base of the skull in the range >95% with collapse of internal carotid)
• Total occlusion¹

Clinical manifestations

• Asymptomatic
• TIA
• Stroke

Anterior cerebral stroke:

• Contralateral weakness and sensory loss in lower limb
• Abulia (lack of motivation for action)
• Akinetic mutism (lack of movement and speech)

Middle cerebral stroke:

• Contralateral weakness and sensory loss of face and upper limb
• Ipsilateral gaze deviation
• Broca’s (expressive) aphasia 
• Wernicke’s (receptive) aphasia
• Contralateral homonymous hemianopia
• Apraxia (inability to perform movements despite having desire and physical ability to do so)
• Neglect

ACA-MCA watershed stroke:

• “Man-in-the-barrel” syndrome (weakness in shoulders and hips bilaterally)

Ophthalmic artery:

• Amaurosis fugax (sudden and temporary loss of vision)

Examination

• Bruits over carotid arteries (best heard with the bell)
• Neurological and Cardiac exam
• Fundoscopy: cholesterol emboli

Differential diagnosis

• Arteriosclerotic disease (most common)
• Non-arteriosclerotic
  • Fibromuscular dysplasia
  • Dissection
  • Vasospasm
  • Aneurysm
  • Arterio-venous fistula
  • Vasculitides (Takayasu’s or Giant cell)
  • Carotid body tumour
  • Migraine with aura

Investigations 

Imaging:

• CT angiography (gold standard)
• MR angiography
• Carotid Duplex Ultrasound
• Digital Subtraction Angiography (for procedural planning)²

Treatment

Medical management

• Lifestyle modification
• Antiplatelets
• Statins
• Blood Pressure control
• Glucose control

Surgical management

Indications:

• Asymptomatic stenosis >70% (provided surgical risk is <2% and life expectancy >5 years)
• Symptomatic stenosis >50% 
• High risk of stroke

Surgical options:

• Carotid endarterectomy
• Carotid artery stenting (when surgery is high risk)

Complications and Prognosis

Complications of stenosis

• Ischaemic stroke and all that comes with it
• Depression

Complications of endarterectomy and artery stenting

• Postoperative cerebral haemorrhage
• Cranial nerve injury
• Haematomas
• Stroke
• Myocardial infarction
• Restenosis
• Hyperperfusion syndrome – sudden increase in blood flow causing headaches, seizures and intracerebral haemorrhage

Prognosis

• Prognosis depends on degree of stenosis

References

1. Lal BK, Bulbulia R. Carotid artery stenosis. In: BMJ Best Practice [Internet]. 2024 [cited 2025 Nov 19]. Available from: BMJ Best Practice
2. Cucchiara BL. Evaluation of carotid artery stenosis. In: Kasner SE, Eidt JF, Mills JL, editor. UpToDate [Internet]. [updated 2024 Jan 04; cited 2025 Nov 19]. Available from: UpToDate
3. Paraskevas KI, Mikhailidis DP, Ringleb PA, Brown MM, Dardik A, Poredos P, et al. An international, multispecialty, expert-based Delphi Consensus document on controversial issues in the management of patients with asymptomatic and symptomatic carotid stenosis. Journal of Vascular Surgery. 2024;79(2):420-35.e1. https://doi.org/10.1016/j.jvs.2023.09.031