Magnetic Resonance Imaging scanning, commonly referred to as an "MRI scan", is a non-invasive way to render images of the inside of an object.
"Cranial MRI" refers to a type of brain scan, or neuroimaging, that gives a detailed examination of the brain. No X-rays are used. The typical scans that are done in children with developmental delays give doctors information about whether all the important structures of the brain are present. These scans do not give information about how the brain functions.
Although research studies have shown differences in the size of certain brain areas in autism, most children with autism do not have an abnormality that will show up on an MRI scan. Even if a difference is noted (such as a hypoplastic or underdeveloped cerebellum), the presence or absence of this finding does not help clarify whether a child has autism or not. A scan does not give useful information about how well a child will do over time, or which therapies will help.
Children who have very large heads (macrocephaly) or very small heads (microcephaly) should be seen by a child neurologist or developmental pediatrician, and an MRI scan may be recommended in these situations. MRI scans will also be recommended for children with epilepsy (two or more seizures without fever) and for the child who appears to be losing developmental skills (see Childhood Disintegrative Disorder).
Autistic children with white, unpigmented areas of skin (hypopigmented patches) may have tuberous sclerosis, which can be diagnosed by MRI scan.