Autism (cont.)
Is autism genetic?
Because many different disorders can result in autism, this question is
complex. Certainly, disorders such as the fragile X syndrome and tuberous
sclerosis, which are both associated with autism, are inherited. There are many
families with more than one autistic child where the autism is not clearly due
to another cause. Recent studies have found that the gene for at least one kind
of familial autism may be on chromosome 13. In some families, autism seems to be
passed from generation to generation. In other families, autism is not found in
prior generations, but affects multiple siblings (brothers or sisters). The
results of this research makes it likely that at least one "autism gene" will be
found soon.
However, the majority of individuals with autism do NOT have a
strong family history, which supports the premise that environmental or a
combination of environmental and genetic factors contribute to the development
of autism. In this context, environmental is meant to indicate any non-genetic
factor, including infections, toxins, nutrition, or others.
How is autism diagnosed?
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 usually not
brought to the attention of a practitioner until several years later in many
cases. If there is a period of normal development, it cannot extend past age
three.
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;
behavioral audiometry and 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 BAER, 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 is may be no need for a
brain CT ("CAT 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 autistic persons by speech pathologists will provide not
only detailed information as to the nature of the language deficits incurred by
the autistic 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.
Next: How is autism treated? »
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