Simulation of posterior fossa cyst by normal, hypo-echoic white matter on cranial ultrasonography.

Ultrasonography in the diagnosis of fetal abnormalities is well documented, and improvements in technology have made possible detailed visualization of the intracranial anatomy. Ten per cent of major fetal abnormalities involve the head and neck. A case of simulation of a posterior fossa cyst by normal, hypoechoic white matter on cranial ultrasonography is presented. Potential pitfalls and the differential diagnosis of intracranial abnormalities in utero are discussed.