A Chiari malformation (sometimes called an Arnold Chiari) is a neurological disorder where part of the brain, the cerebellum (or more specifically the cerebellar tonsils), descends out of the skull into the spinal area. Chiari malformations affect females more often than males. These defects develop during fetal development. Much less commonly, Chiari malformations can occur later in life. This can happen when an excessive amount of cerebrospinal fluid is drained away because of injury, infection, exposure to toxic substances.
A Chiari malformation can also cause pressure on the brain and produce hydrocephalus (pressure due to excessive cerebrospinal fluid accumulation in the brain) and the spinal cord, potentially causing a wide variety of symptoms.
Signs & Symptoms
Children with Chiari I malformations may start to have symptoms as early as age 2 or 3. Some don't have any symptoms until they are older. The signs and symptoms of Chiari malformation can vary greatly from one person to another. Symptoms may go through periods of exacerbation and remission. Specific symptoms can occur in different combinations and generally reflect dysfunction of the cerebellum, the brainstem, the spinal cord and lower cranial nerves.
Chiari malformation is diagnosed by MRI (Magnetic Resonance Imaging). This test is to detect brain stem and spinal cord compression. An MRI (Magnetic Resonance Imaging - a non-invasive test which uses a large magnet to create a picture of internal organs) can clearly show if the cerebellar tonsils are out of position. Unfortunately, there is no single, objective test which can clearly say that someone has a Chiari malformation which is causing problems. The diagnosis of a Chiari II malformation can be made prenatally through ultrasound.
Chiari is more common than many people think. Conquer Chiari estimates that 1 in 1,000 people have Chiari, which translatesto 300,000 people in the US alone. According to the American Association of Neurological Surgeons, there are over 10,000 Chiari surgeries each year