Type I

This type of malformation is a displacement of a portion of the hindbrain, the cerebellum, below its normal position. Many cases are asymptomatic and do not require treatment. However, a variety of symptoms can occur including headache, pain, numbness, vocal cord dysfunction, swallowing difficulty and others. Surgery is typically required for such cases.

Type II

This condition relates to the brain abnormalities associated with some types of spina bifida, particularly myelomeningocele. Hydrocephalus, displacement of the cerebellum and symptoms similar to the Chiari I malformation may occur.

Type III

This is an unusual condition in which a portion of the hindbrain protrudes through a defect in the bone and brain membranes in the back of the head and upper cervical region.