Fig. 2. Analysis of hydrocephalus progression in Tg737^orpk mutant mice using T2 RARE MRI. Compartments containing CSF appear white while brain matter is gray. (A,C) Dilatation is evident in the lateral ventricles (white arrowheads) of 1-day-old mutants as compared with wild types. (E) By contrast, there is no sign of expansion in the fourth ventricle or in the aqueduct (arrows) at this age. (B,D) By day 6, the lateral ventricles of the mutants are markedly enlarged (white arrowheads), without overt differences in the (F) fourth ventricle and aqueduct, but protuberance is seen on the skull above the cerebellum (gray arrowheads). (D) In the subarachnoid space, no difference is detected between wild-type and mutant animals (black arrowheads). Scale bar: 10 mm. (G) Quantitative measurement of the relative ventricular volume in mutant and wild-type controls at each age (n=4; ^*P<0.05).