Cerebrovascular adaptation in chronic hydrocephalus

This study characterizes the regional changes in vascularity, which accompa nies chronic progressive hydrocephalus. Fifteen dogs underwent surgical ind uction of hydrocephalus and were used for histologic studies. Animals were divided into 4 groups: surgical control, short term (less than or equal to5 weeks), intermediate term ((8 weeks), and long term (10 to 12 weeks). Vess el diameter, density, and luminal area were calculated by imaging quantific ation after manual vessel identification in the cortical gray, white matter , and caudate nucleus. Capillary vessel diameter decreased 23.5% to 30.2% ( P < 0.01) in the caudate, but then returned to normal at 12 weeks. Capillar y vessel density decreased 53.5% (P < 0.05) in the cortical gray, but then increased to 234.8% (P < 0.01) over surgical controls at 12 weeks. There wa s no initial decrease in capillary density in the caudate; however, the lon g-term group capillary density was significantly greater (172.8% to 210.5%, P < 0.01) than surgical controls. Overall, there was a short-term decrease in lumen area, with recovery in the longer term. Glial Fibrillary acidic p rotein (GFAP) immunohistochemistry demonstrated the pattern of GFAP stainin g and reactive astrocytes differed in the caudate compared with the occipit al cortex. This data suggest that an increase in capillary density and diam eter may be an adaptive process allowing maintenance of adequate cerebral p erfusion and metabolic support in the hypoxic environment of chronic hydroc ephalus.