congenital anomalies in central (periventricular) position (Chiari malformations, Dandy-Walker syndrome, agenesis of corpus callosum, anencephaly, aqueductal stenosis, holoprosencephaly, encephaloceles)
periventricular hemorrhage (subarachnoid / subdural blood that is nearer transducer are harder to identify - may be confirmed by CT).
vascular malformations (e.g. vein of Galen malformation).
sensitivity for hypoxic–ischemic lesions is poor (normal sonogram does not exclude this pathology);
cerebral edema is hyperechoic - very difficult to diagnose since there is no adjacent parenchymal organ that can provide reference in echogenicity.
definite infarction is hypoechoic and well demarcated.
Normal brain US:
A. Coronal section at level of internal capsule: interhemispheric fissure (long arrow), cingulate sulcus (two short arrows); callosal sulcus (short arrow), sylvian fissure (arrowhead), corpus callosum (cc), frontal horn (1), 3rd ventricle (2), caudate nucleus (3), thalamus (4), internal capsule (5), putamen and globus pallidus (6), insula (I), temporal lobe (T).
B. Coronal section at level of ventricular atria: lambdoid suture (LS), glomus of choroid plexus (white arrow), slightly hyperechogenic periventricular white matter (7).