FIG. 1.

The 6 brainstem AVM subtypes. A: The anterior midbrain AVM, lateral view. This AVM is located on the anterior midbrain surface, is supplied by P₁ PCA branches (posterior thalamoperforating artery [PosThaP] and peduncular perforator [PedP]) and is drained by anterior veins (median anterior mesencephalic vein [MAPonMesV], peduncular vein [PedV], and posterior communicating vein [PComV]). B: The posterior midbrain AVM, lateral view. This AVM is located on the posterior midbrain surface, is supplied bilaterally by the PCA (long circumflex perforators from P₁ and P₂ segments) and SCA (s₃ branches), and is drained by veins ascending to the vein of Galen (tectal vein [TecV], vein of the cerebellomesencephalic fissure [VCMesF], and superior vermian vein [SVerV]). C: The anterior pontine AVM, lateral view. This AVM is located on the rectangular surface between the basilar sulcus medially, the trigeminal root laterally, and the pontomesencephalic and pontomedullary sulci. It is supplied unilaterally by the s₁ SCA and a₁ AICA branches, as well as direct branches from the basilar trunk, and drains to the MAPonMesV medially or the superior petrosal vein [SPetrV] laterally. D: The lateral pontine AVM, lateral view. This AVM is located on the triangular surface of the pons and brachium pontis between the CN V root medially and the V-shaped cerebellopontine fissure laterally. It is supplied unilaterally by the a₂ and a₃ AICA branches and is drained by the SPetrV. E: The anterior medullary AVM, lateral view. This AVM is located below the pontomedullary sulcus, between the anterolateral sulci, and anterior to hypoglossal nerve rootlets. It is supplied by branches from the distal VA and is drained in the midline by the median anterior medullary vein (MAMedV) and MAPonMesV. F: The lateral medullary AVM, lateral view. This AVM is located below the pontomedullary sulcus, lateral to the anterolateral sulcus, and posterior to hypoglossal nerve rootlets. It is supplied by branches from the VA and PICA and drains medially (MAMedV) and/or laterally (lateral medullary vein [LMedV]). PreCenCblV = precentral cerebellar vein; ICV = internal cerebral vein; VPonMesS = vein of the pontomesencephalic sulcus; LAPonMesV = lateral anterior pontomesencephalic vein; VCPonF = vein of the cerebellopontine fissure; TrPonV = transverse pontine vein; VCMedF = vein of the cerebellomedullary fissure. Reproduced with permission from Lawton: Seven AVMs: Tenets and Techniques for Resection, Thieme, 2014.