13. Differential diagnosis for autism

Some conditions may be confusingly similar to autism and one must be careful when making a final determination about a child's disorder and its management. Any condition that may be associated with language delay, especially those that are treatable, must be considered.

• Hearing loss: Every child with a language delay must have a hearing test. A child with a hearing impairment will not have the autistic features as mentioned by the DSM IV criteria, but may present with "pervasive ignoring," production of unusual sounds, "poor eye contact" because he can't coordinate his eyes to the direction of the sound, some temper tantrums due to the frustration caused by the lack of the ability to express his needs, and some other features. These kids however, will never fully qualify for the full diagnostic criteria of the PDD's and this is a reason why a diagnosis can't be based on only a part of the diagnostic requirements. A patient with deafness who is appropriately treated will make a rapid recovery of his lost language if treated early. For this reason, a hearing test is always important to obtain in a child with a speech delay (even if the parents think he can hear) because the hearing loss may be partial or selective to different frequencies. Many children with autism will have some pervasive ignoring of other people that may render a conventional hearing test ineffective. These children will benefit from having a BAER (Brainstem Auditory Evoked Response) where electrodes register the brain's response to sound delivered by earphones to the child. In most situations, this test will have to be performed under sedation.
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• Landau Kleffner Syndrome or acquired epileptiform aphasia: This is a rare condition in which children, mostly older than 3 years of age but occasionally younger, develop seizure activity that includes seizures involving the left hemisphere (the speech areas) and nocturnal status epileptics. These kids commonly, but not always, present with convulsive seizures and have associated autistic regression and loss of acquired speech. Because of that, it is recommended to obtain an EEG (sleep deprived or 24 hour recording) on those autistic children who have a history of loss of acquired speech and behavioral regression. This condition can be successfully treated with anti-epileptic drugs and ACTH.
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• Mental retardation: Another condition that may mimic autism is mental retardation. It may present with speech delay and if severe enough, self-stimulatory behaviors and other "autistic characteristics" may be associated.

• Childhood schizophrenia: This is rare and may mimic autism. This condition usually develops after 5 years of age is associated with a higher I.Q. score (more than 70) than what is found with autism.