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.
The mean age was 40 ± 16 years; mean follow-up was 49 ± 56 months; 75.8% demonstrated syringomyelia. The complication rate was 21.8% with permanent surgical morbidity of 3.2% and surgical mortality of 1.3%. Of the patients, 73.6% reported improvement after 3 months; 21% were unchanged. Overall, 14.3% demonstrated a neurological deterioration within 5 years and 15.4% within 10 years. The severity of neurological symptoms correlated with the grade of arachnoid pathology. Outcome data correlated with the number of previous decompressions, severity of arachnoid pathology, handling of the arachnoid, type of duraplasty, and surgical experience. First-time decompressions with arachnoid dissection and an alloplastic duraplasty resulted in surgical morbidity for 2.0%, a 0.9% mortality rate, postoperative improvement after 3 months for 82%, and neurological recurrence rates of 7% after 5 years and 8.7% after 10 years.