🧠 Artery of Percheron (AOP) is a rare vascular variant where a single perforating artery supplies both paramedian thalami (± midbrain). This is unusual because most cerebral arteries respect the midline.

📖 About

First described in 1973 by French neurologist Gérard Percheron.
Supplies bilateral paramedian thalami (≈30% of cases).
Important cause of acute coma with otherwise normal early CT.

⚙️ Pathophysiology

Occlusion → bilateral medial thalamic infarcts ± midbrain involvement.
🛌 Classic triad: altered mental status, vertical gaze palsy, memory disturbance.
Coma occurs due to involvement of the thalamic–reticular activating system.

🧩 Anatomy

Usually, each medial thalamus has its own arterial supply.
AOP arises from a single P1/P2 segment of the PCA → bifurcates to supply both thalami.
Common error: It comes from the PCA, not the posterior communicating artery.

📊 Epidemiology

Rare: 0.1–2% of all ischaemic strokes.
A typical UK stroke centre (~1,000 cases/yr) may see only 1–2 cases annually.

🧬 Aetiology

Cardioembolic (AF, LV thrombus) or artery-to-artery embolism.
Less common: vertebral artery dissection.

🧲 MRI Appearance

🎯 “Butterfly sign”: bilateral paramedian thalamic infarcts.
🪶 “V sign” in interpeduncular fossa (seen in ~67%).

🩺 Clinical Presentation

Acute coma 🛌 or profound somnolence.
Vertical gaze palsy 👀 and pupillary abnormalities (± pinpoint pupils).
⚡ Memory/cognitive deficits often persist.
If midbrain involved → hemiplegia or CN III palsy.

🔑 Mnemonic: AOP → “3 C’s”: Coma, Cognition, Cranial nerve palsy.

🔍 Differentials (Coma with normal CT)

Meningoencephalitis 🦠
Opiate/sedative overdose 💊
Pontine stroke 🧠
Post-ictal state ⚡
Hypoglycaemia 🍬

🧪 Investigations

Bloods: FBC, U&E, CRP, ESR, cholesterol.
Cardiac: ECG + Holter, echo (look for AF or thrombus).
CT: often normal early; later → thalamic hypodensity.
MRI DWI: diagnostic (butterfly/V-sign).
CTA/MRA: may show vertebral dissection.
LP: usually normal, rules out infection.

💊 Management

Immediate ABC support.
Thrombolysis/thrombectomy if within window (rarely achieved due to delayed Dx).
If diagnosis uncertain → treat empirically for infection until confirmed.
Standard secondary prevention: antiplatelets, BP control, statins.
Neurorehab + neuropsychology for cognitive recovery.

📌 Exam Pearl: “Coma + normal CT” → always think of Artery of Percheron infarct as a differential.

📚 References

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Artery of Percheron stroke