Compared between the trans-fontal US & spiral Ct scan exam in the diagnosis of congenital hydrocephalus, A series of 100 infants with age range of (20 days to 12 months) were studied over a period of 2 years in Teaching hospital in Al diwaniya city. The commonest type of hydrocephalus in this study were obstructive type (83%).The US exam showing (100%) sensitivity in detection the lateral ventricle dilatation as in spiral CT can , with (97%) in detected the 3rd ventricle dilatation in compared with (100%) for spiral CT scan & (64%) in diagnosis 4th ventricle dilation with (100%) .Trans-fontal US exam showing highly sensitivity in early diagnosis of congenital hydrocephalus, with relatively low sensitivity in differentiation between the obstructive & non-obstructive type (low sensitivity in detection the 4th ventricle).In conclusion trans-fontal US exam can be used as a first choice diagnostic test in the diagnosis of congenital hydrocephalus, and CT scan should be preserved for bony & parenchymal abnormalities.
