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Screen for autism
Early referral to intervention
programs is crucial
by Keith J. Goulden, MD
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Over
the past few years, autism spectrum disorders (ASD) have increasingly
been making the news. There's the question of whether autism is triggered
by childhood vaccinations, for example, which makes headlines at more
or less regular intervals, even though the majority of research now
indicates that no such link exists. As well, the media report a "surge"
of ASD being diagnosed, and it's unclear if any of this rise is due
to an actual increase in ASD, since most of it is accounted for by
higher sensitivity and changing criteria for diagnosis. The American
Academy of Pediatrics (AAP) has just published two statements on ASD
screening1
and management,2
and Barbaresi et al recently came out with a good academic review
for primary care pediatricians.3
What are
autism spectrum disorders?
ASD, autism, and pervasive developmental disorder (PDD) are labels
used for a disability that involves social communication impairment;
which label is used depends on whether the impairment is "typical"
(i.e. fulfills the criteria for an autistic disorder) or "atypical."
Social communication is the skill required to share non-verbal information
and is necessary to understand the feelings, intentions, interests,
etc. of others. In addition to an impairment in this kind of communication,
individuals with ASD have many other problems, such as repetitive
behaviours (usually due to sensory processing difficulties) and
resistance to change, paired with anxiety and obsession, so often
pictured in portrayals of the disorders. See Table
1 for a summary of diagnostic criteria.
Children with ASD and intellectual impairment
have a significant delay in verbal language development, while older
and higher functioning individuals, for instance with Asperger's
syndrome, may be quite verbal. Even people with an intact intellect
may display impaired use of pragmatic language and frequently misunderstand
sarcasm. Because most people with ASD are intellectually impaired,
the term "higher functioning" usually indicates that they're
broadly in the range of normal functioning, not necessarily gifted.
On the other hand, much of what we know about the condition comes
from a few people with ASD who are extremely bright. One example
of a very capable person with ASD is Temple Grandin,5
who has a PhD in Animal Science and makes her living designing humane
animal handling facilities when she isn't speaking or writing about
ASD.
The "spectrum" of ASD isn't all
that wide from the perspective of the core disability in social
communication: even a "mild" impairment in this area is
a serious functional limitation in our increasingly complex social
world. It's the additional disabilities (such as the range of intellect)
that produce the widest variation in overall function. Just like
everybody else, individuals with ASD have a temperament and personality
that may alter the appearance of their disability; some are easy-going
or passive, while others are more prickly or oppositional.
All people with ASD have difficulties interacting
with others; a few are capable of functioning independently, but
most require assistance in a group setting. Young children present
either with a delay in the communication skills that should emerge
during the second year of life, or with the behavioural problems
associated with their sensory processing difficulties and/or anxiety
disorder. Older individuals may attract attention because of social
difficulties or the maladaptive behaviours they use to help cope
with social distress and rigidity. Take Tim's and Patrick's cases,
for example. Both children have ASD, although they show very different
presentations and levels of function. They both have a disorder
of social communication that identifies their disability as ASD.
What causes
autism?
ASD is usually idiopathic (i.e. associated with no other identified
condition), but may also be caused by another disorder. The brain
dysgenesis or injury from fragile X syndrome, Down's syndrome, tuberous
sclerosis or fetal alcohol spectrum disorder may all produce ASD.
For instance, while Down's syndrome usually causes an intellectual
disability, it's associated with ASD in about 10% of cases, which
makes a big difference in the treatment and outcome.
Although it doesn't often run in the family,
ASD is estimated to be 90% heritable6
and caused mainly by "susceptibility genes." The model
of susceptibility genetics suggests that we all may carry a small
number of these genes, but a larger number is necessary to pass
the threshold for the disorder to develop. This may explain the
"shadows of autism" or broader phenotype seen in the extended
family of those with ASD. The same model is also being used to help
us understand a number of other developmental disabilities such
as attention deficit hyperactivity disorder (ADHD).
Because there's no definitive information
on the genes involved, there are no specific tests available to
help a family understand the cause of their particular child's primary
ASD. The recurrence risk for the family of a child diagnosed with
primary ASD is currently estimated at 10% (remember that the recurrence
risk for secondary ASD depends on the underlying condition).
Prenatal testing isn't available, and these families often worry
for a number of months after the subsequent child is born. Research
is underway in Canada to find earlier diagnostic tests.7
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