If a Chiari malformation occurs with other congenital (present at birth) defects, the diagnosis may be made at birth. The occurrence of Chiari malformation has thought to be one in every 1,000 births but, with the increased use of diagnostic testing, it may be much more common. Other times, the diagnosis is made after the onset of specific signs and symptoms, and after diagnostic testing. The doctor obtains a complete prenatal and birth history of the child and may also ask if there is a family history of any medical problems. The doctor will also ask about developmental milestones, such as the age the child sat up, crawled, or walked since a Chiari malformation can be associated with other neuromuscular disorders. Developmental delays may require further medical follow-up for underlying problems.
During the examination, a measurement of the circumference of the child's head is taken and compared to a scale that can identify normal and abnormal ranges.
Diagnostic tests that may be performed to confirm the diagnosis of a Chiari malformation include:
- X-rays. A diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones and organs onto film.
- Computed tomography scan (also called a CT or CAT scan). A diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce horizontal, or axial, images (often called slices) of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat and organs. CT scans are more detailed than general X-rays.
- Magnetic resonance imaging (MRI). A diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.