IN-VIVO H-1 MR SPECTROSCOPIC IMAGING AND DIFFUSION-WEIGHTED MRI IN EXPERIMENTAL HYDROCEPHALUS

The severity and progression of ventricular enlargement, the occurrenc e of cerebral edema, and the localization of ischemic metabolic change s were investigated in a rat model of hydrocephalus, using in vivo H-1 MR spectroscopic imaging (SI) and diffusion weighted MRI (DW MRI). Hy drocephalic rats were studied 1, 2, 4, and 8 weeks after injection of kaolin into the cisterna magna, Parametric images of the apparent diff usion coefficient (ADC) revealed a varying degree of ventriculomegaly in all rats, with different time courses of ventricular explansion, Ex tracellular white matter edema was observed during the early stages of hydrocephalus, most extensively in cases of progressive ventriculomeg aly. In gray matter regions, ADC values were not changed, compared wit h controls. In case of fatal hydrocephalus, high lactate levels were o bserved throughout the whole brain. In all other rats, at all time poi nts after kaolin injection, lactate was detected only in voxels contai ning cerebrospinal fluid. This suggests accumulation of lactate in the ventricles, and/or an ongoing periventricular production of lactate a s a consequence of cerebral ischemia in experimental hydrocephalus.