Chiari malformation occurs when the section of the skull containing the cerebellum is too small or is deformed, thus putting pressure on and crowding the brain. The lowermost portion, or tonsils, of the cerebellum are displaced into the upper spinal canal. The pediatric form, Chiari II malformation, is always associated with a myelomeningocele. The adult form, Chiari I malformation, results primarily from a small back portion of the skull.
When the cerebellum is pushed into the upper spinal canal, it can interfere with the normal flow of cerebrospinal fluid (CSF) that protects your brain and spinal cord. This impaired circulation of CSF can lead to the blockage of signals transmitted from your brain to your body, or to a buildup of spinal fluid in the brain or spinal cord. Alternatively, the pressure from the cerebellum upon the spinal cord or lower brainstem can cause neurological signs or symptoms.
Some of the symptoms are:
Headaches, often severe, are the classic symptom of Chiari malformation. They're typically precipitated with sudden coughing, sneezing or straining. People with Chiari malformation type I also can experience:
- Neck pain (running down the shoulders at times)
- Unsteady gait (problems with balance)
- Poor hand coordination (fine motor skills)
- Numbness and tingling of the hands and feet
- Difficulty swallowing (sometimes accompanied by gagging, choking and vomiting)
- Vision problems (blurred or double vision)
- Slurred speech
- Ringing or buzzing in the ears (tinnitus)
- Poor bladder control
- Chest pain, in a band-like pattern around the chest
- Curvature of the spine (scoliosis) related to spinal cord impairment
- Abnormal breathing — specifically, sleep apnea characterized by periods of breathing cessation during sleep
In Chiari malformation type II, a greater amount of tissue protrudes into the spinal canal compared with type I. The signs and symptoms can include those related to a form of spina bifida, called myelomeningocele, that always accompanies Chiari II malformation. In myelomeningocele, the backbone and the spinal canal have not closed properly before birth.
Chiari malformation type III
In one of the most severe types of the condition, Chiari malformation type III, a portion of the lower back part of the brain (cerebellum) or the brainstem extends through an abnormal opening in the back of the skull. This form of Chiari malformation is obvious at birth or by intrauterine ultrasound.
Chiari malformation type IV
In people with the even more severe Chiari malformation type IV, the brain itself has never developed normally. This form is also obvious at birth or by intrauterine ultrasound.