LEARNING-DEFICITS IN CONGENITALLY HYDROCEPHALIC RATS AND PREVENTION BY EARLY SHUNT TREATMENT

Shunt surgery is the usual treatment for infantile hydrocephalus; howe ver, the extent to which it avoids subsequent neurological deficits is uncertain. The effect of early-onset hydrocephalus was tested in I-I- Tx rats using the Morris water maze. Spatial learning was assessed at 21 days after birth in control (n = 18), hydrocephalic (n = 18) and hy drocephalic rats shunt-treated at 4-5 (n = 7) or at 10-12 days of life (n = 13). The time taken to find a hidden platform was measured in fi ve trials on 2 consecutive days and the data analyzed by one- and two- way ANOVA and t-tests. The latencies of the control rats decreased sig nificantly between the first and second trial on the Ist day, and lear ning was retained until the 2nd day. The hydrocephalic group had longe r latencies than controls on both days, with no significant decrease b etween any trials. Performance was not significantly different between the two shunt groups. Overall, the shunted rats had latencies which w ere not significantly different from controls but were significantly l ower than hydrocephalics. Despite this, the shunted rats did not perfo rm as well as the controls. It is concluded that, although shunt treat ment improved learning, some effects of early-onset hydrocephalus may not be reversible and/or a longer recovery time is required.