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Interesting as most vascular supply respects the midline. This is a single vessel that supplies bilateral structures.

About

• The artery of Percheron was first described in 1973 by French Neurologist Gerard Percheron.
• It is interesting as it is an artery that provides vascular to two paramedian structures as most brain end arteries respect the midline and do not supply bilateral structures.
• It can produce a classical clinical presentation as seen below.
• 30% have a single artery supplying bilateral paramedian thalamus

Pathophysiology

• This is a single vessel that supplies bilateral structures.
• Usually there are bilateral medial thalamic infarcts and perhaps the involvement of the midbrain
• May have altered mental status, vertical gaze palsy, and memory impairment
• Reduced awareness and coma likely as thalamus is the top of the reticular activating system

Anatomy

• Usually there is an artery on either side supplying the right and left medial thalamus.
• Note there is an error in the graphic so read Posterior cerebral artery and not the posterior communicating artery.

Epidemiology

• Acute Artery of Percheron infarcts represent 0.1 to 2% of total ischaemic stroke
• A typical stroke centre with 1000 strokes per annum may see 1-2 cases per annum

Aetiology

• The arterial supply of the thalamus and midbrain is complex and is provided by perforating branches from the posterior cerebral artery and the posterior communicating artery.
• Many numbers of significant variations in the vascular supply of thalami and mesencephalon are seen. The Artery of Percheron is a vascular variant in which a single dominant thalamo-perforating artery arises from one P1/2 segment of PCA and bifurcates to supply both paramedian thalami.
• Occlusion of this vessel results in a characteristic pattern of bilateral paramedian thalamic infarcts with or without mesencephalic infarctions.
• Aetiology is likely cardioembolic or artery to artery from the aorta or vertebral

MRI appearance

Clinical

• Result of bilateral damage patient is unresponsiveness and acute coma.
• Somnolescence - patient is unresponsive but may roll over and pull up bed clothes as if sleeping.
• Coma in others even needing intubation.
• Pinpoint pupils may be seen unless IIIrd nerve involved
• Long term when awakens memory and cognition often affected
• Midbrain involvement - may have hemiplegia, IIIrd nerve deficits

Differentials in Comatose patient with normal initial CT

• Meningo-Encephalitis
• Opiates or other sedatives
• Pontine strokes
• Post ictal
• Hypoglycaemia
• Post concussion

Investigations

• FBC, U&E, LFTs. CRP. ESR. Cholesterol
• ECG/24 hr tape for AF / PAF
• Echo for cardioembolic causes
• CT: usually normal but may show bilateral thalamic hypodensity with time
• MRI: classical bilateral "butterfly" medial thalamic infarcts and may show some midbrain involvement. There may be the V sign of hyperintense signal intensity on axial FLAIR and DWI images along the pial surface of the midbrain in the interpeduncular fossa in 67% in cases of AOP infarction with midbrain involvement.
• CTA/MRA to look for vertebral dissection can be useful as a cause
• LP may be normal mildly elevated protein but may help exclude infective process if suspected

Management

• ABC, support acutely. Often delayed diagnosis as stroke as other non-stroke diagnoses need exclusion
• Consider thrombolysis and /or thrombectomy if appropriate. However often the presentation is difficult, and diagnosis delayed and beyond the window for thrombolysis.
• Uncertainty means that one may give antibiotics, antivirals initially as ?? Meningitis/Encephalitis. LP may be normal or mildly elevated protein.
• Can make a good recovery. But there may remain memory and cognitive issues.
• Manage as other ischaemic strokes. Look for embolic sources.
• Standard Care: Antiplatelets, BP medications, Statin
• Neurorehabilitation: cognitive issues may predominate so involve Neuropsychology

References

• Jeremy D. Schmahmann. Vascular Syndromes of the Thalamus
• Artery of Percheron Infarction: Imaging Patterns and Clinical Spectrum