The lower part of the brain (called the cerebellum) sits at the back of the skull above the spine. With a Chiari malformation, the space for the cerebellum is either too small or unusually shaped1. This can cause part of the cerebellum to push into the funnel-like opening1 at the bottom of the skull (called the foramen magnum) and into the space occupied by the spinal cord.
There are several types of Chiari malformations, but the most common type in the children we serve is a Chiari 1 malformation. The development of a Chiari 1 malformation can be related to abnormal growth of the facial bones or skull (craniofacial conditions). A Chiari 2 malformation is a specific type found most often in children with spina bifida. Chiari 3’s are more severe malformations and may not support life.
Children with complex craniosynostosis (a condition where joints between the bones of the skull fuse, or close, too early) or a craniofacial syndrome (abnormalities of the face and skull and possibly other areas) are at risk for developing a Chiari malformation.
The exact cause is not known. Suspected causes include early joining together of the bones of the skull that enclose the brain and the joints that form the skull and raised pressure within the skull. Blood flow and heart valve problems and hydrocephalus (an accumulation of spinal fluid associated with increased pressure in the skull) may also be a cause.
For children with craniofacial conditions, the Chiari malformation may develop in the first months of life and worsen over time. This may be due to the lower part of the brain growing too much while that part of lower part of the skull remains unusually small.
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 problems gaining weight.
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, difficulty sleeping, depression and headache made worse by coughing or straining. Hand coordination and fine motor skills may also be affected.
It’s important to note that not all children with Chiari malformations develop symptoms. Children with a high risk of developing a Chiari malformation are monitored with MRI imaging studies. Sleep studies may also be used to determine if breathing is affected.
In some instances, surgery to enlarge the space within the back of the skull may be needed to treat a Chiari malformation. This may involve surgery to reshape the bones of the back of the skull or remove bone at the back of the skull.
1Chiari Malformation, KidsHealth.org