A Chiari malformation is a defect in the portion of the brain that controls balance (the cerebellum. The malformation causes brain tissue to extend into the spinal canal, and it usually forms during fetal development, typically due either to a genetic mutation or as a result of poor maternal nutrition during pregnancy. As the skull develops, the portion at the rear base of the skull doesn’t grow to a normal size. The smaller space puts pressure on the cerebellum and blocks the flow of protective fluid that normally surrounds the brain and spinal cord. Less commonly, Chiari malformation can develop later in life as a result of injury, infection or exposure to some toxins. There are four types of Chiari malformations. The most common type (type I) can be congenital or acquired later in life. Type II (also called classic Chiari malformation) is only present in children with spina bifida. Type III and type IV are very rare and usually are associated with severe neurological problems.
Some Chiari malformations cause no symptoms, while others can experience symptoms like:
Symptoms can vary significantly, depending on the type that’s present, with type I malformations often causing no symptoms unless the malformation is severe.
When a Chiari malformation causes symptoms or poses a threat to the central nervous system, it must be treated with surgery to stop the progression of the symptoms and damage. Surgery helps relieve pressure on the brain and the spinal cord and re-establish normal circulation of cerebrospinal fluid. Several techniques are used to treat Chiari malformations, including procedures to remove a small portion of the skull or the bones that form the spinal canal. Both these surgeries expand the space in the area and relieve compression. Surgery can also be used to remove a portion of the dura, the durable membrane that covers the brain and spinal cord, to promote better circulation of the cerebrospinal fluid. Other techniques may also be used to relieve compression and correct related conditions.