What is a Chiari Malformation?
A condition in which brain tissue extends into the spinal canal, Chiari Malformaiton occurs when part of your skull is abnormally small or misshapen, pressing on your brain and forcing it downward.
Structural adnormalities in the physiagonmy of the brain and spinal cord typically cause Chiari malformation. These defects develop during fetal development. Due to genetic mutations or a gestational diet that lacked certain nutrients, the indented bony space at the base of the skull develops abnormally small.
The surgeon typically diagnoses Chiari Malformation after an MRI scan, usually following obvious, abnormal protrusion of the cerebellum toward the spinal cord. Special MRI studies can measure the direction and degree of fluid motion around the Chiari malformation. Scientists have discoverd 3 types of Chiari Malformation.
Chiari malformation type I
In Chiari malformation type I, signs and symptoms usually appear during late childhood or adulthood. Headaches, often severe, are the classic symptom of Chiari malformation. They generally occur after straining physically such as exertion, coughing, or sneezing.
Less often, people with Chiari malformation may experience:
- Tinnitus – a sensation of hearing whereby ringing or buzzing presents in the ears
- Weakness & Muscle Instability
- Slow or Irregular heart rhythm
- Scoliosis or Other Impairments related to the Curvature of the spinal cord
- Abnormal breathing, such as central sleep apnea, which is when a person stops breathing during sleep
Chiari malformation type II
Chiari malformation type II results when more tissue extends into the spinal canal than type I. The signs and symptoms can include those related to a form of spina bifida called myelomeningocele that nearly always accompanies Chiari malformation type II. In myelomeningocele, the backbone and the spinal canal haven’t closed properly before birth.
Signs and symptoms may include:
- Difficulty breathing or Swallowing
- Fast eye movements pointing downward
- Instability and Weakness in the motion of the arms
Usually noted with ultrasound during pregnancy or after birth in infancy, Chiari II requires early diagnosis.
Chiari malformation type III
In one of the most severe types of the condition, Chiari malformation type III, a portion of the brainstem extends through an large, atypical opening in the back of the skull. This form of Chiari malformation, diagnosed at birth or with an ultrasound during pregnancy, typically has a higher mortality rate and may also cause neurological problems.
How common is a Chiari Malformation?
Early estimates of Chiari Malformation predicted the condition occuring in about one in every 1,000 births. However, advancedments in the technology and accessibility of the MRI and other diagnostic imaging has revealed that Chiari malformation may be much more common than previously thought.
Only Chiari Malformation Type I may have a hereditary component and the malformation can run in families.
How is a Chiari Malformation typically treated?
Specialists typically treat patients with Chiari I malformations with minimal symptoms without syringomyelia quite conservatively. Analgesics, muscle relaxants, and soft collars typically alleviate mild neck pain and headaches.
For more severe cases, a procedure known as posterior fossa decompression creates more space for the cerebellum, relieving pressure on the spinal cord. The surgeon makes an incision at the back of the head and removes a small portion of the bone at the bottom of the skull, a process known as a craniotomy.