The term Chiari malformation is used when part of the lower part of the brain (cerebellum) lies below the opening at the bottom of the skull (foramen magnum). There are several types, but the most common type in children with craniofacial conditions is a Chiari 1 malformation. A Chiari 2 is found in children with spina bifida. Chiari 3’s are severe malformations and may be incompatible with life.
Children with complex craniosynostosis or a craniofacial syndrome are at risk for developing a Chiari malformation. The exact cause is not known but suspected causes include the premature fusion of cranial vault and cranial base sutures, raised intracranial pressure, venous hypertension and hydrocephalus. For children with craniofacial conditions, it is thought that the Chiari malformation may be a progressive condition that develops in the first months of life. This may be due to disproportionate growth of the lower part of the brain while the lower part of the skull is unusually small. In some craniofacial syndromes, such as Pfeiffer syndrome, up to 80% of children develop Chiari malformations.
Symptoms of Chiari malformation in infants include difficulty swallowing, irritability when being fed, excessive drooling, a weak cry, gagging or vomiting, arm weakness, a stiff neck, breathing problems, developmental delays, and an inability to gain weight. Not all children with Chiari malformations develop symptoms. For toddlers and older children symptoms may include breathing problems, neck pain, balance problems, muscle weakness, numbness or other abnormal feelings in the arms or legs, dizziness, vision problems, difficulty swallowing, ringing or buzzing in the ears, hearing loss, vomiting, insomnia, depression, or headache made worse by coughing or straining. Hand coordination and fine motor skills may be affected.
Children with a high risk of developing a Chiari malformation are followed with MRI studies. Sleep studies may also be used to determine if breathing is affected.
In some instances, the child may require a surgery called a posterior cranial vault expansion to treat their Chiari malformation. In selected cases, treatment of the posterior cranial deformity by occipital vault remodeling and treatment of the Chiari-like deformity by suboccipital decompression can be carried out using the same surgical procedure.