Chiari malformations can be difficult to diagnose, since the symptoms can be vague, or there may be no symptoms at all. A definitive diagnosis is generally made after an MRI scan, where the abnormal protrusion of the cerebellum toward the spinal cord can be seen. In some cases, the diagnosis may be incidental, meaning that a patient who undergoes an MRI scan for another reason may be diagnosed with Chiari when the scan reveals the abnormality – in these cases the patient may not have experienced any symptoms at all (see Pictures of Chiari).
Anyone who receives a tentative diagnosis of Chiari should always be referred to a neurosurgeon, who will conduct an evaluation and recommend a course of treatment.
In addition to an MRI scan of the brain, an MRI of the entire spinal column is useful. In some patients with Chiari, a cyst (known as a syrinx or syringomyelia), forms within the spinal column. Symptoms of leg numbness or scoliosis are more likely when a syrinx exists. There are also special MRI studies that can measure the direction and degree of fluid motion around the Chiari malformation. This MRI can help in the decision-making process regarding treatment.
Treatment may not be necessary at all when no symptoms are present. When an asymptomatic patient is diagnosed with Type I Chiari, regular monitoring by a neurosurgeon may be all that's needed. (See Doctors Who Treat Chiari.)
Type I Chiari, once diagnosed, is rarely progressive. However, since a small number of patients may show progressive symptoms or MRI changes, ongoing monitoring is recommended. Treatment for Type I Chiari relies on a surgical procedure aimed at making more room at the site of compression. The results of treatment for CM-I are excellent, with the majority of patients experiencing partial or complete resolution (80 to 90%) with few or no complications. (See Surgery for Chiari.)
Type I Chiari can be corrected with surgery to relieve the pressure on the spinal column. Surgery usually produces excellent results with few or no complications. In patients with hydrocephalus, a minimally invasive procedure called endoscopic third ventriculostomy (ETV) can drain the fluid.
Reviewed by Jeffrey Greenfield, Ph.D., M.D.
Last reviewed/last updated: April 2021