The essential features of autism are the significantly impaired or abnormal development of communication and social interaction and the abnormally restricted repertoire of behaviors, activities, and interests. This disturbance in normal development must manifest itself prior to age three. While many parents report normal development in the first year of the child, there is actually limited opportunity to observe this, as the child is often not brought to the attention of a practitioner who has specific experience in diagnosing autism until several years later in many cases. If there is a period of normal development, it cannot extend past age three. As the early onset of the disorder is a key component in its diagnosis, it is important that practitioners screen for the possible presence of autism in all children from infancy on.
Any person with a delay or regression (loss) of language or an abnormality of social interaction beginning prior to the age of three may be suspected of being autistic. The medical evaluation begins with a thorough medical history and physical examination. This examination should be performed by a practitioner not only familiar with autism, but with other disorders that may appear similar to or mimic the symptoms of autism. The practitioner should have particular expertise in the neurological examination of impaired individuals, as subtle findings may lead the examiner down a particular diagnostic path. For example, the presence of mild weakness or increased reflexes on one side of the body will lead the examiner to conclude that a structural abnormality in the brain is present and that an MRI examination of the brain is appropriate.
The history and physical examination will point the examiner to specific diagnostic testing to evaluate for other conditions associated with autism or developmental delay. Any child who has a language delay should have his or her hearing formally evaluated. It is not sufficient to simply determine whether or not a person being examined is able to hear. In order for normal language development to proceed, the individual must have sufficient hearing capabilities at low volumes in the high frequency range. Therefore, even if the person turns his or her head to a clap or shout, he or she may still have enough of a hearing deficit to inhibit language development.
There are two types of hearing tests; 1) behavioral audiometry; and 2) brainstem auditory evoked responses (BAER).
- Behavioral audiometry is performed by a skilled clinical audiologist. The person being examined is placed in a room and his or her responses to different tones are observed.
- For the brainstem auditory evoked responses (BAER) test, the individual is sedated and earphones are placed over the ears. Tones of different volumes and frequencies are played and the electrical response of the brain is monitored.
If the he or she is capable, behavioral audiometry is the preferred method primarily because sedation is not required. Depending upon specific features of the examination and history, the practitioner may want to obtain blood and urine samples for specialized testing to evaluate for some of the inborn errors of metabolism and to obtain DNA for chromosomal studies and fragile X testing.
If the neurological examination is normal, there may be no need for a brain CT scan or MRI scan. However, if the neurological examination is suggestive of a structural brain lesion, then a neuroimaging study, preferably an MRI, should be performed. Newer imaging procedures such as SPECT or PET scans are used primarily as research tools and have no place in the initial evaluation of the autistic individual. In very specialized instances, such as the autistic person with difficult-to-control seizures, such tests may be useful.
The evaluation of individuals with autism by speech pathologists will provide not only detailed information as to the nature of the language deficits incurred by the afflicted individual, but will also be the first step in formulating a specific treatment plan with respect to language. Occupational assessment may be particularly helpful in determining the day-to-day strengths and vulnerabilities of the individual with autism (for example, sensitivity to clothing and food texture) and assist those who care for the person in promoting his or her strengths and compensating for their challenges.
Given the complex and far-reaching symptoms and effects of autism, it is generally thought that the most accurate and thorough diagnosis of this disorder is obtained by group of practitioners from various disciplines, also called a multidisciplinary team, that includes a pediatrician, speech and occupational therapists, educators, and often psychiatrists and others.
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