Magnetic resonance imaging study of extracellular fluid tracer movement inbrains of immature rats with hydrocephalus

Hydrocephalus is associated with brain compression and accumulation of neur otransmitter waste products in the brain and cerebrospinal fluid. We postul ated that the extracellular compartment is compressed and specifically hypo thesized that extracellular fluid tracer movement through brain would diffe r between control and hydrocephalic rats. Gadolinium diethylenetriamine pen taacetic acid (Gd-DTPA) was injected into the cerebral cortex of 4-week-old rats, 7-11 days after induction of hydrocephalus by kaolin injection into the cisterna magna. The movement of this soluble paramagnetic compound was followed over successive timed intervals from 20 min to 180 min with T-1-we ighted magnetic resonance imaging. Non-hydrocephalic controls exhibited gre ater spread of the tracer and greater change in T-1-weighted signal intensi ty in the ipsilateral cortex than hydrocephalic animals. Hydrocephalic anim als exhibited preferential accumulation of tracer in edematous white matter . Gd-DTPA penetrated the lateral ventricles within 30 min in both control a nd hydrocephalic rats. The results suggest that there is a relative impairm ent of extracellular fluid movement through the cerebral cortex of young hy drocephalic rats.