A Chiari Malformation is anatomically described as cerebellar tonsillar ectopia below the level of the foramen magnum. In other words, the cerebellum has descended to a level where it should not exist. It is a pediatric condition, however, it is often diagnosed in late adulthood, given the manifestation of symptoms at a later age and the various ways in which it can present clinically.

Chiari Malformations present with a variety of symptoms. The most common symptom is an occipital headache that worsens with position or with a bowel movement. Other associated symptoms are tinnitus and chest pain. Given the tonsillar ectopia and its compression upon the brainstem, it can result in dysphagia, uvula deviation, and other symptoms of cranial nerve compression.

It is often associated with a syringomyelia, also called a syrinx, which is a fluid filled cystic cavity in the spinal cord. This forms due to disruption in CSF flow secondary to the ectopia of the cerebellar tonsils. Clinically, patients may have scoliosis on physical exam. Symptomatically, this presents as loss of pain and temperature sensation in the upper extremities.