An accurate, confirmed diagnosis is generally impossible until after birth, though prenatal diagnosis using fetal ultrasonography (ultrasound) can identify characteristic physical abnormalities. After birth, diagnosis may be delayed for several months because the infant's early behavior appears to be relatively normal. The most accurate diagnostic techniques are thorough clinical evaluation (considering physical findings and a detailed patient history); advanced imaging techniques, such as angiography, computerized tomography (CT scan), and magnetic resonance imaging (MRI); and (more rarely) transillumination. However, diagnostic literature fails to provide a clear distinction between severe obstructive hydrocephalus and<unk> , leaving some children with an unsettled diagnosis. Preliminary diagnosis may be made in utero via standard ultrasound, and can be confirmed with a standard anatomy ultrasound.<unk>  is sometimes misdiagnosed as bilaterally symmetric schizencephaly (a less destructive developmental process on the brain), severe hydrocephalus (cerebrospinal fluid excess within the skull), or alobar holoprosencephaly (a neurological developmental anomaly). Once destruction of the brain is complete, the cerebellum, midbrain, thalami, basal ganglia, choroid plexus, and portions of the occipital lobes typically remain preserved to varying degrees. The cerebral cortex is absent; however, in most cases, the fetal head remains enlarged due to increased intracranial pressure, which results from inadequate reabsorption of the cerebrospinal fluid produced in the choroid plexus.
Hydranencephaly
Hemihydranencephaly
Microhydranencephaly
Schizencephaly
Megalencephaly
Holoprosencephaly
Lissencephaly
Microlissencephaly