The neurobiological differences in the cerebrum between persons with developmental stuttering and their fluently speaking peers

Developmental Stuttering (DS) is a speech disorder which is characterized by repetitions, prolongations, or pauses that disrupt the normal flow of speech. It occurs in approximately 5-8% of the pre-school children and recovers spontaneously in 70-80% of the cases, resulting in a prevalence of about 1% in adolescence. However, unrecovered people who stutter (PWS) can experience lifelong negative consequences, like participation restrictions, irritation and embarrassment. It is known that DS has a clear genetic basis, that PWS have increased dopamine activity, and that the severity of stuttering can be reduced by dopamine blockers. Here we describe functional and structural grey and white matter abnormalities that are present in PWS. It appears that the precentral gyrus (primary motor cortex), inferior frontal gyrus (IFG), superior temporal gyrus (STG), middle temporal gyrus (MTG), supplementary motor area (SMA), middle frontal gyrus (MFG), rolandic operculum (RO) and corpus callosum (CC) are important key players in DS. Although not all data support each other in all details, here we attempt to give a shared overview of current research and its directions, both in adults and children with DS. It has become clear that some brain differences already exist during childhood rather than resulting from compensatory attempts, and can therefore be used as markers for the development and monitoring of DS. Increased knowledge about DS could potentially open new ways for treatment of PWS, and may prevent the symptoms of persistent DS. This could results in less anxiety, shame, and irritation during social interaction, and would make the life of millions of stutterers a lot easier and more pleasant.