Chiari malformation type 1 (CM1) is a congenital anomaly of the cerebellum — the part of brain located at the base of the skull. In CM1, the tissue in the lower part of the cerebellum protrudes into the spinal canal, which can obstruct cerebrospinal fluid from flowing into the spinal canal. This causes pressure on surrounding tissues. If it is not treated appropriately, Chiari malformation type 1 can impact virtually all functions of the brain.

The presentation of CM1 usually includes some kind of head pain — classically, a headache at the back of the head while coughing, sneezing or exerting. Other common symptoms can be diffuse numbness, tingling, pain or heaviness into the neck, trunk, arms and legs.

The list of less common symptoms is very long and can involve sensory and motor changes throughout the body. The presentation of CM1 in children and adults is similar, though younger children tend to have more brainstem dysfunction, while older children and adults have more sensory problems. Both children and adults may experience:

  • Breathing difficulties
  • Chiari dropping attacks or brief fainting spells
  • Swallowing difficulties 

In children, Chiari malformation occurs equally in boys and girls. In adults, it is three times more common in women than in men.

While the cause of Chiari malformation in children and adults is unknown, it is thought to begin in the early stages of brainstem and spinal cord development. In some cases, it is related to the back of the skull being atypically small.

The treatment of CM1 and its associated symptoms generally involves decompression surgery at the base of the skull. In this procedure, specially trained neurosurgeons remove bone and enlarge the lining of the brain — often using the patient's own tissue — to create excess space for cerebrospinal fluid and to reestablish normal circulation of the fluid.

While recovery from the surgery can be challenging, most patients experience near complete resolution of their symptoms. Our experienced medical team will develop a personalized treatment plan that helps patients achieve the best possible outcome.

Chiari malformation type 1 sometimes is associated with the development of syringomyelia — a fluid-filled cyst in the spinal cord. The surgical treatment for CM1 usually also corrects the syringomyelia.

At UChicago Medicine, children and adults with Chiari malformation are treated by neurosurgeons who are world-renowned for their expertise in these procedures. In most cases, the neurosurgeon has undergone significant pediatric training in the treatment of this malformation and related syndromes.