Children are most commonly diagnosed with Aicardi Syndrome between the ages of three months and five months, if they meet the following criteria:

• Female sex (or XXY genotype male)
• Retinal lacunae -- lesions of the retina
• Seizures -- typically beginning as infantile spasms, a type of epileptic disorder in infants
• Absence of the corpus callosum (complete or partial)
  

The classic criteria remain the cornerstone of diagnosis in most patients. However, in rare cases, one of the features, especially lack of development of the corpus callosum, may be missing. The diagnosis can probably be made in such cases if two or more of the criteria below are present:

• abnormal formations in the brain, usually microgyria where the bumps on the brain are abnormally narrow
• Periventricular and subcortical heterotopia (a misplacement of groups of neurons in the brain sometimes found in seizure disorders)
• Cysts around the 3rd ventricle and/or choroid plexuses cysts in specific areas of the brain
• Papillomas of choroid plexuses (a benign, non-cancerous tumor found in a specific section of the brain )
• Optic disc/nerve coloboma (a congenital notch in the optic nerve)

• abnormal ribs or spine
• Microphthalmia -- a condition where eyes may be smaller than normal
• Other eye abnormalities, such as coloboma
• "Split-brain" EEG (dissociated suppression-burst tracing)
• Gross asymmetry -- large size differences between the two halves of the brain

• An eye exam will be performed to confirm retinal involvement. Other occasional findings with the eye exam will be micropthalmia and coloboma. The degree or level of vision varies from normal to blindness.
• CT scan of the head or MRI of head can confirm lack of development of the corpus callosum, brain cysts, or other brain abnormalities.
• EEG can be used to help determine the type and severity of seizures.