Welcome to our talk today, which is on a subject that's very near and dear to my heart,
the genetics of stuttering, a clinically difficult but scientifically fascinating disorder.
My name is Dennis Drayna, I'm a Senior Investigator and currently Scientist Emeritus
at the National Institute on Deafness and Other Communication Disorders,
which is part of the National Institutes of Health, in the United States.
I'd like to start with talking about what stuttering is, the natural history of the disorder.
Stuttering is a disorder of the flow of speech, characterized by repetitions or prolongations
of syllables or words, and by silent interruptions in speech known as blocks.
The disorder typically arises in childhood, about the time children are learning
how to talk, and it's common.
The incidence rate has been estimated that as many as 5 per cent of children
in the world stutter at some point, as they're learning how to speak,
or in the early preschool years.
Fortunately, something like 75 to 80 per cent of these cases resolve,
either spontaneously or with the help of speech therapy, but not all do
- and I think I'll speak for myself here, but I think some of my clinical colleagues
in speech and language pathology would agree with me -
that the therapy for this difficult disorder is less than satisfactory.
I think about a third of the subjects who undergo speech therapy
for stuttering have a clear lasting success;
about a third have good temporary success - they'll develop good speech fluency,
but after a while, they'll begin to regress back to some stuttering;
and there's maybe a third of people who are just extremely treatment-resistant,
for reasons that we don't really understand.