My original
(brief) response to you, G.B, was that Rett's has nothing to do with
TS (Rett's is only diagnosed in females, involves loss of head circumference
growth and motor coordination in hand skill and gait, and fits in the
Asperger/Autism cluster in the 4th edition of the Diagnostic and Statistical
Manual -- DSM-IV). While I'm by no stretch of the imagination
an expert in Rett's Disorder, allow me to elaborate a little further
now though........
You are
of course right that there are many aspects of Austism/Aspergers that
people with disinhibition disorders also experience (particularly the
overstimulation stuff -- getting internally overloaded by sensory information,
or overwhelmed by one's own amplified neurology, etc,). If backed into
a corner I would likely say that Austism/Aspergers would probably have
more in common with TS than Rett's would. I had the pleasure of sharing
an office with a high-functioning autistic woman (also getting her Ph.D.)
during my graduate training and we often remarked, as have you, about
the many similarities autism and TS have. I also get many questions
at my presentations concerning
the relationship of these two disorders.
Pervasive
Developmental Disorders (autism/aspergers/retts/childhood disintegrative
disorder), while they share many of the features of disinhibition, go
further than this though. These disorders can severely compromise ABILITY
-- disinhibition is about leaky brakes alone. People with PDD's can
experience leaky brakes, PLUS deficits in cognition, language abilities
(expressive and receptive language difficulties in Rett's, for instance),
and motor problems in the area of intentional movements (while those
with TS have tics, they are intermittant -- our actual willed motor
abilities aren't sacrificed the way they are in Rett's for example).
Some researchers
suggest that the fundamental difference in PDD's and disinhibition-type
disorders is that the latter is about intention editing alone (in other
words having a good "goalie" to keep things from slipping
past the posts when you don't want them to) while the former involve
"theory of mind" problems in addition to these frontal lobe
issues (a disruption in thinking, in essence).
All that
being said, most people with PDD's seem to display disinhibition because
they are further "up" the spectrum than TS, but most people
with disinhibition problems DON'T have PDD's because they are "lower"
on the spectrum (this is analogous to how most people with TS demonstrate
features of ADHD even though most people with ADHD do not demonstrate
features of TS). One study I read suggested that 6.5% of individuals
with Autism warrant an actual diagnosis of TS. I wonder, based on conversations
with my old office-mate though, if this underestimates the occasions
that tics are part of PDD.
I hope
this clarifies sir! Take good care G.B.,
Dr. Dunc.
