Because cerebrospinal fluid (CSF) diversion can successfully treat children with hydrocephalus, the distinction between hydranencephaly and hydrocephalus is critical.[5] This distinction is also important in prognostic terms, as well as in connection with family support. However, differentiating hydranencephaly from hydrocephalus and alobar holoprosencephaly in the prenatal period can be challenging; in difficult cases, prenatal magnetic resonance imaging (MRI) can be used to establish the correct diagnosis (see MRI).
In utero, hydranencephaly is frequently diagnosed with ultrasonography (see the following images); postnatally, cranial ultrasonography can detect the absence of cerebral tissue (see Ultrasound). However, MRI is probably the best modality for the overall evaluation of the anomaly and for the documentation of cortical remnants.[6, 7]