MAGNETIC-RESONANCE-IMAGING AND BEHAVIORAL-ANALYSIS OF IMMATURE RATS WITH KAOLIN-INDUCED HYDROCEPHALUS - PREHUNTING AND POSTSHUNTING OBSERVATIONS

The motor and cognitive dysfunction associated with hydrocephalus rema ins a clinical problem in children. We hypothesized that young rats wi th hydrocephalus should exhibit similar dysfunction and that the dysfu nction should be reversible by shunting. Hydrocephalus was induced in 3-week-old rats by injection of kaolin into the cisterna magna. Rats w ere assessed by Ta-weighted images obtained with a 7-T magnetic resona nce device and by repeated behavioral testing including ability to tra verse a narrow beam and ability to find a hidden platform in a water p ool. Some of the rats underwent a shunting procedure 1 or 4 weeks afte r kaolin injection. Magnetic resonance images were used to measure ven tricle size. They clearly demonstrated increased signal in periventric ular white matter, which corresponded to increased brain water content . A how-void phenomenon was observed in the cerebral aqueduct. Ability to traverse the beam did not correlate with the degree of ventriculom egaly. Ability to swim to the hidden platform demonstrated a progressi ve impairment of learning function which may have been accentuated by motor disability. When rats were shunted after 1 week, the behavioral dysfunction was prevented. Late shunting after 4 weeks was associated with gradual recovery of the behavioral disability which was not compl ete after 4 weeks. We conclude that early shunting is superior to late shunting with regard to behavioral dysfunction. High-resolution MR im aging shows features in hydrocephalic rats similar to those found in h ydrocephalic humans. (C) 1997 Academic Press.