Cerebellar hypoplasia is a neurological condition in which the cerebellum is smaller than usual or not completely developed.

Cerebellar hypoplasia may be caused by thyroid abnormalities, environmental influences such as drugs and chemicals or viral infections or stroke.

Cerebellar hypoplasia is a feature of a number of congenital (present at birth) malformation syndromes, such as Walker-Warburg syndrome. It is also associated with several inherited metabolic disorders, such as Williams syndrome, and some of the neurodegenerative disorders that begin in early childhood, such as ataxia telangiectasia.

In an infant or young child, symptoms of a disorder that features cerebellar hypoplasia might include:

• Floppy muscle tone
• Developmental or speech delay
• Problems with walking and balance
• Seizures
• Mental retardation
• Involuntary side to side movements of the eyes

In an older child, symptoms might include:

• Headache
• Dizzy spells
• Clumsiness
• Hearing impairment

The prognosis is dependent upon the underlying disorder. Some of the disorders that are associated with cerebellar hypoplasia are progressive, which means the condition will worsen over time, and will most likely have a poor prognosis. Other disorders that feature cerebellar hypoplasia are not progressive, such as those that are the result of abnormal brain formation during fetal development, and might have a better outcome.

There is no standard course of treatment for cerebellar hypoplasia. Treatment depends upon the underlying disorder and the severity of symptoms. Generally, treatment is symptomatic and supportive.