Prenatal diagnosis of moderate unilateral hydrocephalus subsequently not requiring neonatal decompression.

Prenatal diagnosis of unilateral hydrocephalus is unusual. In the past most such cases have been treated with neonatal shunting procedures. We present an unusual case in which moderate unilateral hydrocephalus was diagnosed prenatally at 30 weeks' gestation. Despite prenatal and neonatal sonographic signs of both cortical thinning and mild displacement of midline intracranial structures, confirmed by computed tomography, neonatal shunting was not required. The findings and course in this unusual case suggest that infrequently some of the milder cases of idiopathic nonprogressive unilateral hydrocephalus discovered later in life may possibly represent late detection of this preexisting condition.