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Four variants of the paramedian thalamic–mesencephalic arterial supply: (A) Variant 1 – normal anatomy; (B) Variant 2a – the left P1 segment is the wellhead of both paramedian arteries; (C) Variant 2b – illustrates the PeA; (D) Variant 3 – in this anatomical variant, an arcade gives rise to the paramedian arteries connecting the left and right P1 segments. BA: Basilar artery; M: Midbrain; PCA: Posterior cerebral artery; PeA: Percheron artery; T: Thalamus
