《Slide 49.》Arterio-venous malformation , Brain(Cerebrum)
A. Brief Descriptions：
AVM is the most important type of vascular malformation ; abnormal communication between arteries and veins ; 90% in the cerebral hemispheres.
Congenital or secondary to trauma, inflammation, or healed ruptured aneurysm.
Bleeding AVMs of brain and development of seizures.
B. Gross Findings：
Tangle network of numerous、worm-like、abnormally tortuous misshapen vascular channels.
C. Micro Findings：
Tangles of abnormal vessels of various diameter seperated by gliotic tissue in the absence of intervening capillary bed often with evidence of prior hemorrhage.
Some vessels have the thin collagenous walls of veins，whereas others the muscular and elastic laminae of arteries or structural hybrids.
Artery feeding a vein.
Arterialization of vein: abnormally thick-walled veins.
Elastic stains identify arteries and focal loss or duplication of elastin.
Crescents of mural calcification may outline the contours of some vessels.
Variable gliosis or hemosiderin-stained interposed brain parenchyma.
Congestion of the vessels、thrombi.
Abnormal communication between arteries and veins.
Absence of intervening capillary bed.
Robbins Pathologic Basis of Disease, 6th ed. P.1313.
【 Fig. 49-1 (LP)】Proliferation of variant sized blood vessels (left) in the surface of brain; note cerebral parenchyma in the right.
【 Fig. 49-2 (LP)】Tangles of abnormal vessels of various diameter, some vessels have the thin collagenous walls of veins, whereas others the muscular and elastic laminae of arteries or structural hybrids.
【 Fig. 49-3 (HP)】Thick and thin walled vessels without intervening capillary bed.