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 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
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
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.
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.
Because many patients with Chiari malformation are symptom free, the disorder is often discovered only in the process of diagnosis or treatment for a separate medical condition. If you, or your child is experiencing any of the symptoms above, don’t hesitate to visit a doctor. Chiari malformation can usually be detected quickly and easily with an x-ray, CT scan, or MRI and a physical exam.
Treatment for Chiari malformation can vary based on the severity of the condition. If a patient isn’t experiencing any symptoms, then the physician will most likely recommend no treatment apart from monitoring the condition. If symptoms include headaches or other forms of pain, the doctor might recommend various pain medications. However, when Chiari malformation causes, or is at risk of causing, damage to the central nervous system, appears that it could grow worse over time or is accompanied by severe symptoms, it can only be treated with surgery.
In both type I and type II Chiari malformations, the goal of surgery is twofold. First, the surgeon seeks to relieve pressure that is being put on the brain and the spinal cord. Second, they are looking to re-establish normal fluid movement through and around the area.
The most common surgery for treating Chiari malformation is known as posterior fossa decompression surgery. This procedure involves the removal of a small portion of the lower skull to create more space for the cerebellum and to relieve pressure on the spinal column. Most of the time, the surgeon will also open up the dura mater, the covering of the brain, in order to provide more room and to allow normal fluid circulation.
Chiari malformation can also be treated with a spinal laminectomy, which relieves pressure on the spinal cord through the removal of part of the roof of the spinal canal. This increases the size of the canal and removes pressure from the spinal cord and nerve roots.