Arnold-Chiari malformation is a condition in which the cerebellum portion of the brain protrudes down into the spinal canal. It may be congenital, associated with other anomalies including myelomeningocele, syringomyelia and spina bifida. Hydrocephalus (increased intracranial fluid and pressure) dominates the clinical picture in infants.
The symptoms most often begin during infancy, although they may be delayed until adolescence or adulthood.
Symptoms usually include vomiting, muscle weakness in the head and face, difficulty in swallowing and varying degrees of mental impairment. Paralysis of the arms and legs may also occur.
As they grow older, adults and adolescents with Arnold-Chiari malformation who previously were asymptomatic may show signs of progressive brain impairment, such as involuntary, rapid, downward eye movements.
Other symptoms may include dizziness, headache, double vision, deafness, an impaired ability to coordinate movement and episodes of acute pain in and around the eyes.
Children with Arnold-Chiari malformation may require surgery to repair an existing myelomeningocele. Hydrocephalus may be treated with surgical implantation of a shunt to relieve increased pressure on the brain. Some adults with Arnold-Chiari malformation may benefit from surgery in which the opening in the back of the skull is enlarged to relieve intra-cranial pressure.
Most patients who have surgery experience a reduction in their symptoms. Some patients may experience prolonged periods of relative stability. Infants with very severe malformations may have life-threatening complications.
Reviewed by Dr Andrew Rose-Innes, Yale University School of Medicine