New Research into Stuttering

From information compiled from CNN and Science News websites


The New England Journal of Medicine has published research about the genetic factor in stuttering. While it has been known that the condition is hereditary in many cases, exactly what physiological traits are passed down to cause it has been a mystery.

The research was carried out by a team effort by different research centres from around the world, including the National Institute of Deafness and Other Communication Disorders, the National Human Genome Research Institute and the Center of Execellence in Molecular Biology at the University of the Punjab, Lahore, Pakistan.

In a study conducted on a large extended Pakistani family in which stuttering was common, three genetic mutations in brain cells were discovered. This condition was found only in the family members who stuttered and, not surprisingly, occur in the part of the brain that controls speech.


The study also involved people who stuttered from a wider population sample who were not related, and a group of randomly chosen people who did not stutter. Dr. Dennis Drayna is a researcher at the National Institute on Deafness and Other Communication Disorders, and co-authored the study.  He explained to CNN that the cell mutations “affect a process inside cells that degrades things that the cells don’t need anymore.” Because of the mutations, this process is interrupted.
This part of the cell, called the lysosome, is like a recycling centre. It breaks down old proteins and other unuseable material. For many of the stutterers in the study, the specific genes that direct proteins to the lysosome are mutated and the recycling process is stalled, resulting in a build up of the unwanted material. This somehow leads to speech disturbance.

Not all people who stutter have this particular genetic condition. The mutation also occurs in people who do not stutter, indicating that its presence presents higher risk of stuttering but does not cause it in all cases.

Out of the three million cases of people who stutter in the United States, Dr. Drayna estimates that this mutation is a factor in 140,000 of those individuals. (CNN website)

What does this mean for people who stutter? It could mean more effective treatment. Not all stutterers have this specific mutation, some do not: isolating the specific gene that is causing stuttering in an individual could help determine the type of therapy he or she is given.

The discovery also puts to rest a common belief that people who stutter are just nervous or suffer from a psychological disorder.

Robert Marion, a geneticist at the Children’s Hospital at Montefiore and Albert Einstein College of Medicine in New York City suggests that infants who positively test for the gene could be started earlier on speech therapy in a preventative measure.
For more information about this, consult the original research article in the New England Journal of Medicine (available online at cost, or at the library of your nearest post-secondary educational institution). There is also some interesting commentary on this discovery on the Stuttering Brain blog (http://thestutteringbrain.blogspot.com/) and an excellent video and podcast on the StutterTalk website.

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