Artery of Percheron territory infarct

Artery of Percheron territory infarct is rare, on account of the relative rarity of the artery of Percheron, and presents with a variety of signs and symptoms collectively termed the paramedian thalamic syndrome. It is a type of posterior circulation infarction.

On imaging, it is classically characterized by bilateral infarcts in areas involving the rostral midbrain and/or ventromedial thalamus.

Clinical presentation

The symptoms may vary following infarct extension through thalamic or mesencephalic structures ²:

• bilateral paramedian thalamic involvement is usually characterized by a triad of altered mental status, vertical gaze palsy, and memory impairment
• when also accompanied by rostral midbrain lesions, a mesencephalothalamic or thalamopeduncular syndrome occurs, which includes other oculomotor disturbances, hemiplegia, cerebellar ataxia, and movement disorders, along with the triad mentioned above

Radiographic features

There are four major patterns of artery of Percheron infarction, all of which bilaterally involve the paramedial thalamus ^2,3:

• bilateral paramedian thalamic and midbrain infarction (most common)
• isolated bilateral paramedian thalamic infarction
• bilateral paramedian thalamic and anterior thalamic infarction
• bilateral paramedian thalamic, anterior thalamic and midbrain infarction (least common)  

MRI

Artery of Percheron infarction is best visualized on DWI or FLAIR sequences on MRI and is often missed on initial CT.  The midbrain V sign is a feature demonstrated on 67% of patients with the artery of Percheron infarctions involving the midbrain. This sign appears on axial views of DWI and FLAIR sequences as an area of V-shaped hyperintensity on the pial surface of the midbrain that forms the posterior wall of the interpeduncular fossa ².

History and etymology

Described by the French neurologist Gérard Percheron in 1973.

Differential diagnosis

Possible differential considerations include:

• top of the basilar artery syndrome
• bilateral internal cerebral vein thrombosis (dural venous sinus thrombosis)
• other causes of thalamic restricted diffusion