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In the course of
normal development, the brain integrates and
organizes sensory input from the environment. The
sensory inputs consist of sound, sight, touch,
movement, body awareness, and the pull of gravity.
These sensory integrative experiences form the
building blocks for children's more complex
learning as they mature. But what happens if the
normal sensory integration processes that occur
with maturation are delayed or disordered? What
happens then?
Dr. A. Jean Ayres is
generally credited with developing both a theory of
sensory integration dysfunction and therapeutic
interventions for children suffering from it. Of
particular importance here, her work emphasizes the
importance of three of the senses: tactile,
vestibular, and proprioceptive:
The tactile
(touch) system provides information on light
touch, pain, temperature, and pressure. If a child
suffers from dysfunction in the tactile system, he
may experience light touch or a gentle hug as
intense or aversive, he may find certain kinds of
fabrics or clothing irritating, may refuse to eat
foods of a particular texture, and may avoid
touching or handling certain kinds of objects. We
say that a child is "tactile defensive" when he or
she is extremely sensitive to light touch. When
touched, it is as if the brain is flooded with an
overload of sensory input that it cannot process,
and the child's response may be disorganized and
emotional. How often do we attempt to gently
refocus a distracted child with a light touch on
the shoulder? How often have we seen a
child who seems to be having an exaggerated pain
response to something that we know was "just
minor?" Perhaps we think that the child is just a
"drama queen" or attempting to get our attention,
but could it be
that they are really perceiving the sensory input
differently than we do?
The vestibular
system involves structures within the inner ear
(the semi-circular canals) that detect movement and
changes in the position of your head. If you were
to close your eyes for a moment and tilt your head,
you would know that your head is tilted even
without having the visual input because your
vestibular system provides that information. If a
child's vestibular system doesn't develop or
integrate normally, she may be hypersensitive to
vestibular stimulation and have fearful reactions
to ordinary childhood activities such as swinging
on swings, going down slides, etc. She may also
experience difficulty walking on or negotiating
nonlevel surfaces such as hills or stairs. Children
with this kind of hypersensitive vestibular system
often appear clumsy, but not all clumsy children
have hypersensitive vestibular systems, and not all
children with vestibular dysfunction are
hypersensitive. Some are under- or hyposensitive.
Children with hyposensitive vestibular systems
often engage in what appears to be
sensation-seeking behaviors. They may whirl around
like a dervish, jump, and/or spin.
The proprioceptive
system provides feedback from your muscles,
joints, and tendons that enables you to know your
body's position in space. If there is a disturbance
in the proprioceptive system, the child may be
clumsy, fall, seem to maintain abnormal body
postures, have difficulty manipulating small
objects, and and may resist trying different
movements. If you've ever watched a
student's grip on a writing instrument and noticed
how abnormally tight the grip was, you may have
been seeing an indication of this kind of problem
(although there might be other explanations for the
problem).
When we talk about
sensory processing difficulties or sensory integration dysfunction, we are talking
about some disturbance in the child's ability to
process sensory input. It could be a disturbance in
just one of the sensory systems, or it could
involve two or more systems.
While this brief
overview has focused on three systems (tactile,
vestibular, and proprioceptive), parents and teachers need to
keep in mind that the child can have sensory
defensiveness in any of the sensory systems. For
example, some children will find certain sounds
intolerable (such as the bell signalling change of
periods, or noises in the hallway), while other
children may find particular smells or tastes
intolerable. Any kind of sensory defensiveness can
make it difficult for the child to function
normally in a school setting or to engage in normal
social activities with peers.
If a child appears
significantly impaired by sensory-related issues,
parents may wish to arrange for an assessment by a
qualified occupational therapist. If
sensory-related issues are affecting school
functioning, parents may wish to ask the school
district to arrange for a school-based OT
evaluation, keeping in mind that the scope and
purpose of a school-based OT assessment are
generally somewhat different than an
OT assessment arranged for
privately.
As is often my
advice, let your child's behavior guide you. If
your child seems to have significant trouble
handling what should be "normal" parts of their
childhood -- if they avoid situations that their
peers would enjoy, if they avoid too many foods or
textures, if they avoid playground equipment out of
fear, if they seem to experience normal voice
volumes as "too loud" -- then you may want to
consider an OT assessment.
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Sensory Processing Disorder (SPD) is not yet recognized in the DSM (diagnostic manual), and efforts by its advocates to have it included in the DSM-V have produced only partial success to date. As of December 2008, the DSM-V Committee wrote to the SPD Foundation that the committee needed "a significant number of additional studies" before SPD would be recognized as a distinct disorder and not, perhaps, as a subtype of Autism or ADHD. Whether sufficient reports and evidence can be provided in time remains to be seen. There have been a few preliminary small studies suggesting that SPD may occur by itself (i.e., in the absence of any other disorders), but SPD usually occurs with other disorders.
The SPD Foundation provides information and research on proposed subtypes of SPD.
Having SPD recognized as a subtype of Autism or ADHD would not be a terrible thing for some children, but would not help children who have SPD comorbid with other disorders or who might have SPD without any other disorder.
At the present time, then, there are no firm set of criteria for diagnosing SPD, although there are a number of checklists and scales that a qualified occupational therapist may use as part of an assessment. Parents need to remember that diagnosis requires more than just parents going over a checklist and saying, "Wow, that is really describing my child." A checklist can be a good starting point for pursuing professional assessments that can rule out or indicate other medical or neurological conditions that need to be addressed or treated.
Continue to Page 2, comorbidity and school interventions
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