Chiari malformation is a structural defect which results in brain tissue extending into the spinal canal. This condition is often the result of genetic conditions or poor nutrition during pregnancy and occurs when the skull is misshapen or too small and presses downwards on the cerebellum, the part of the brain that controls balance.
While most Chiari malformations are congenital, meaning they are present from birth, they can occur later in life if too much spinal fluid is produced or drained from the lumbar or thoracic spine because of injury or infection.
There are several classifications of Chiari malformation, ranging from I to IV, and each classification is based on the severity of the malformation.
Chiari Malformation Type I
Chiari malformation type I is the most common form of this condition. It occurs when the indentation of the skull containing the cerebellum is too small or deformed and puts pressure on the brain; forcing the tonsils into the spinal canal.
This type of malformation usually doesn’t cause any noticeable symptoms and is often diagnosed incidentally. However, symptoms of a more severe type of this malformation are usually noted in late childhood or early adulthood and can can include:
Difficulty balancing or swallowing
A headache that results after a cough or sneeze
Numbness or tingling within the feet or hands
Chiari Malformation Type II
This is another relatively common type of malformation that occurs when a greater amount of brain tissue is forced into the spinal canal when compared to a type I malformation. Symptoms of this condition are usually noted during ultrasounds before birth or during early infancy.
Type II Chiari malformation can also occur in instances of hydrocephalus, or water on the brain, where too much cerebral spinal fluid is produced or not absorbed and puts pressure on the brain.
Symptoms of this type of malformation are usually the same as a type of spina bifida called myelomeningocele that almost always occurs in conjunction with Chiari malformation type II. Myelomeningocele is a defect that keeps the backbone and spinal canal from closing normally. Symptoms can include:
Changes in breathing pattern
Swallowing problems and gagging
Quick downward eye movement
Chiari Malformation Type III
Type III is the most serious form of the condition and occurs when a part of cerebellum or the brain stem protrudes through an abnormal opening in the back of the skull and into the spinal cord. Symptoms of this condition are usually first spotted during pregnancy.
This type of malformation often causes severe neurological defects due to the pressure put on the brainstem or spinal cord.
Chiari Malformation Type IV
This is the most rare type of Chiari malformation and occurs when the cerebellum is incomplete or underdeveloped and can usually be diagnosed before birth.