More than one in 1000 people—and it’s hard to tell how many more—exhibit an interesting though not always dangerous condition called a Chiari malformation. Dr. Hans Chiari described the malformation in 1891, though the congenital form was observed as early as 1883. In this condition, the brain is mispositioned within the cranium and extends into the space where the spinal cord normally is. Singer Rosanne Cash and golfer Bobby Jones have been diagnosed with Chiari malformation.
The condition often has no symptoms, which is why it frequently goes undetected. It is often found during a seemingly unrelated examination, particularly an MRI scan related to some condition. It is likely that there are people who neither exhibit symptoms nor have any sort of diagnostic test that would find it, and the condition goes entirely undetected. However, the malformation sometimes causes severe headaches that frequently lead to a diagnosis, along with problems with balance, poor fine motor skills, difficulty swallowing, blurred vision, or tinnitus. Extreme cases can lead to scoliosis and sleep apnea.
The congenital form of Chiari malformation, known as type II, is associated with the birth defect spina bifida. Chiari I malformation occurs later in life, generally as a result of an unusual skull shape that exerts downward pressure on the brain, forcing it into an unusual position. In that position, it presses on the spine, leading to the symptoms of the condition when they do appear. It can also lead to complications such as tethered cord syndrome, in which the spinal cord, moved out of place by the brain, gets stretched around the spine, leading to nerve and muscle damage. People with Chiari malformation sometimes get excess fluid around the brain, which needs to be drained using a shunt.
When the condition has no symptoms and causes no complications, treatment is usually unnecessary, though regular MRI scans should be done to make sure it isn’t moving further and causing damage. Sometimes, a small piece of the skull is removed to give the brain more room and ease the pressure. Alternatively, a portion of the spinal column might be removed instead.