Types of Arnold Chiari Malformation

Type 0 – is a relatively new type defined by no actually herniation seen in the cerebellum but ‘crowding’ of the foramen magnum by the cerebellum. This is not always recognised by doctors in Australia but is considered to have the same symptoms and can lead to the same issues as other types of Chiari.

Type 1 – is the most common type of Chiari seen. It is recognised as at least 5mm herniation of the cerebellum in the spinal canal. The majority of people will have this type. Some people can have this and not get symptoms.

Type 2 – this type not only includes the cerebellum but a herniation of the brainstem (medulla) and 4th ventrical through the foramen magnum into the cervical vertebral canal. It is often associated with meningocele and spina bifida

Type 3 – This includes a form of dysraphism with a portion of the cerebellum and brainstem pushing out through a defect in the back or the head or neck. Its very rare and often fatal or result in severe neurological deficits in surviving patients. Hydrocephelus is also common with this type and people often have other birth defects.

Type 4 – This is the most severe for and the rarest, with this one the cerebeullm fails to develop normally and ther are other associated malformations f the brain and medulla. Most do not survive infancy.