Chiari Syndrome

Abstract

Chiari I malformation (CMI) is a congenital or acquired malformation of the back of the brain. It involves the parts of the brain called the cerebellum, brainstem and the upper spinal cord. The cerebellum is a part of the brain that helps coordinate movement and balance. The brainstem is the main pathway for all signals from the brain to the spinal cord. There is no cognitive or “thinking” function associated with the cerebellum or brainstem, so patients with CMI can have normal cognitive function. A CMI is characterized by descent or “escape” of the cerebellum into the spinal canal through an opening at the base of the skull called the foramen magnum. Normally, the cerebellum is fully contained within the skull; however, in a CMI, a part of the cerebellum called the cerebellar tonsils, can be forced downward or escape into the spinal canal and crowd the spinal cord and brainstem. This part of the cerebellum, the tonsils, can block the normal flow of fluid called cerebrospinal fluid (CSF) around the brain. At the same time the tonsils can compress the cervical spinal cord and brainstem, which are essential for normal brain function.