Makindo Medical Notes

Related Subjects: |Acute Stroke Assessment (ROSIER&NIHSS) |Atrial Fibrillation |Atrial Myxoma |Causes of Stroke |Ischaemic Stroke |Cancer and Stroke |Cardioembolic stroke |CT Basics for Stroke |Endocarditis and Stroke |Haemorrhagic Stroke |Stroke Thrombolysis |Hyperacute Stroke Care

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 because it supplies two paramedian structures, whereas most brain arteries respect the midline and do not supply bilateral structures.
• It can produce a classical clinical presentation as seen below.
• Approximately 30% of cases have a single artery supplying the bilateral paramedian thalamus.

Pathophysiology

• This is a single vessel that supplies bilateral structures.
• Usually, bilateral medial thalamic infarcts occur, possibly with midbrain involvement.
• Symptoms may include altered mental status, vertical gaze palsy, and memory impairment.
• Coma is likely due to thalamus involvement at the top of the reticular activating system.

Anatomy

• Normally, each side of the medial thalamus is supplied by its respective artery.
• The Percheron artery is a vascular variant that arises from a single P1/2 segment of the posterior cerebral artery (PCA) and bifurcates to supply both paramedian thalami.
• Note: There is an error in the graphic - the correct artery is the posterior cerebral artery, not the posterior communicating artery.

Epidemiology

• Acute artery of Percheron infarcts represent 0.1% to 2% of total ischaemic strokes.
• A typical stroke centre with 1,000 strokes per year may see 1-2 cases annually.

Aetiology

• The arterial supply of the thalamus and midbrain is complex, provided by perforating branches from the posterior cerebral artery (PCA) and posterior communicating artery.
• The artery of Percheron is a rare variant in which a single thalamo-perforating artery supplies both thalami.
• Occlusion of this artery results in bilateral paramedian thalamic infarcts with or without mesencephalic infarction.
• The aetiology is likely cardioembolic or artery-to-artery embolism from the aorta or vertebral arteries.

MRI Appearance

Clinical Presentation

• Patients often present with acute coma due to bilateral thalamic infarcts.
• Some patients may display somnolence, appearing unresponsive but able to make small movements (e.g., rolling over or pulling up bed clothes).
• Coma in severe cases, sometimes requiring intubation.
• Pinpoint pupils may be seen unless the third nerve is involved.
• Memory and cognition may be affected long-term after recovery.
• Midbrain involvement can cause hemiplegia or third nerve deficits.

Differentials in Comatose Patients with Normal Initial CT

• Meningoencephalitis
• Opiate or other sedative overdose
• Pontine strokes
• Post-ictal states
• Hypoglycaemia
• Post-concussion syndrome

Investigations

• Blood tests: FBC, U&E, LFTs, CRP, ESR, cholesterol levels.
• ECG and 24-hour Holter monitoring for atrial fibrillation (AF) or paroxysmal AF (PAF).
• Echocardiogram to assess for cardioembolic sources.
• CT: May be normal initially, but may show bilateral thalamic hypodensity later on.
• MRI: Classic "butterfly" bilateral medial thalamic infarcts with or without midbrain involvement. The V-sign of hyperintense signal in the interpeduncular fossa may appear in 67% of cases.
• CTA/MRA can help identify vertebral dissection as a cause.
• LP (lumbar puncture) may be normal or show mildly elevated protein, helpful in ruling out infection.

Management

• Immediate ABC support and management, as the diagnosis may be delayed due to exclusion of non-stroke causes.
• Consider thrombolysis and thrombectomy if appropriate, although diagnosis delays may prevent timely administration.
• Initial uncertainty may lead to treatment for potential infections (antibiotics/antivirals) while awaiting confirmatory tests.
• Patients can make a good recovery, although memory and cognitive deficits may persist.
• Manage as other ischaemic strokes: antiplatelets, blood pressure control, statins.
• Neurorehabilitation, particularly for cognitive recovery, with the involvement of neuropsychology.

References

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