Cerebellar hypoplasia is a neurological condition in which the cerebellum is not completely developed or is smaller than it should be. It may occur with a variety of congenital syndromes, metabolic disorders and neurodegenerative disorders; therefore signs and symptoms may depend upon the associated condition an affected individual has. The most common findings are developmental and speech delay, poor muscle tone (hypotonia), ataxia and abnormal ocular (eye) movements. Cerebellar hypoplasia may range from mild or partial underdevelopment to complete absence (agenesis). It may affect only the cerebellum, or also affect other central nervous system structures. The inheritance pattern may differ depending on the underlying cause of the condition.