Altered diffusion and perfusion in hydrocephalic rat brain: a magnetic resonance imaging analysis

Object. It can be inferred from data published in the literature that brain compression occurs in the early stages of acute hydrocephalus and that dra inage of extracellular waste products is impaired. The authors hypothesized that compression of the cortex would alter water distribution and retard t he diffusion of fluid in the hydrocephalic brain. Methods. Proton diffusion, blood perfusion, and T-1 and T-2 relaxation time s were determined in adult rat brain by using magnetic resonance imaging pr ior to, and 1 and 8 days after induction of hydrocephalus by kaolin injecti on. Five anatomical regions of interest were studied. The striatum, dorsal cortex, and lateral cortex exhibited decreased T-2 and apparent diffusion c oefficient (ADC) values bur no change in perfusion. Examination of white ma tter revealed an initial decrease in ADC followed by a significant increase . The T-2 relaxation times increased and perfusion decreased progressively between 1 and 8 days after induction of hydrocephalus. Conclusions. Acute experimental hydrocephalus causes compression of gray ma tter, perhaps associated with reduction in total water, which impairs diffu sion of water in the tissue. White matter compression and hypoperfusion pre cede the development of edema. These findings have importance for understan ding the neurochemical changes that occur in hydrocephalic brains.