Fault in the brain causes stammering

The cause of stammering, which has eluded scientists for decades, has been found to be an abnormality in the left half of the brain.

Stammering affects one in 100 adults and can lead to frustration and embarrassment for sufferers, who include Pop Idol's runner-up, Gareth Gates.

Researchers knew the cause was genetic but have been unable to uncover its origin and structure. A study in The Lancet, published today, claims that a disconnection in speech-related areas in the brain is to blame.

Dr Martin Sommer and colleagues from the universities of Hamburg and Göttingen in Germany tested 15 people. Using magnetic resonance imaging, they assessed the brain tissue structure of those with a stammer and compared it with a control group of people with normal speech.

They found that the tissue structure of a region in the left hemisphere in stammering patients was significantly different to that in the controls. Fibres in this area connect a number of parts of the brain used for the articulation and planning of speech.

The theory is that the abnormality disturbs signal transmission, disrupting the timing of speech. The right side of the brain overcompensates, causing the stammer.

"This abnormality probably develops during the period of early language and speech acquisition in which many children experience a transient phase of stuttering," Dr Sommer said. "Our methods could be used to ascertain why certain children develop persistent stuttering, whereas others become fluent speakers."

Last year, the British Stammering Association said children with signs of the problem were more likely to overcome it if they received help before reaching school age.