The diagnosis of Dandy-Walker malformation is established by MRI of the brain (Figure 29.1). The fourth ventricle is markedly dilated. The vermis is small and compressed by the dilated fourth ventricle. The posterior fossa is large, the occipital bone protrudes backwards, and the tentorium is raised. Brainstem hypoplasia is present. Dandy-Walker malformation may be associated with dysgenesis of the corpus callosum, neuronal migration abnormalities, and other central nervous system anomalies. Treatment of Dandy-Walker malformation is surgical. More about...117

Figure 29.1.— [A] Large posterior fossa with ventral compression of the brainstem; [B] absence of the cerebellar vermis.

Miller-Dieker syndrome usually presents with seizures. Apnea may occur during a seizure or because of brainstem abnormalities. More about...47

Microscopic or Functional Brainstem Abnormality
Neonates with microscopic or functional brainstem abnormalities do not show evidence of brainstem abnormalities on MRI, yet the pathology is suspected to be in the brainstem. These abnormalities include apnea of prematurity, idiopathic hypoventilation syndrome, startle disease, and feeding apneas.
Apnea of prematurity is a common entity. Neonates with apnea of prematurity usually have signs of global immaturity. Apnea occurs most frequently during active sleep.The apnea may be central, obstructive, or mixed. Excessive periodic breathing is usually present.