Brain anatomy differences in childhood stuttering

Abstract

Stuttering is a developmental speech disorder that occurs in 5% of children with spontaneous remission in approximately 70% of cases. Previous imaging studies in adults with persistent stuttering found left white matter deficiencies and reversed right-left asymmetries compared to fluent controls. We hypothesized that similar differences might be present indicating brain development differences in children at risk of stuttering. Optimized voxel-based morphometry compared gray matter volume (GMV) and diffusion tensor imaging measured fractional anisotropy (FA) in white matter tracts in 3 groups: children with persistent stuttering, children recovered from stuttering, and fluent peers. Both the persistent stuttering and recovered groups had reduced GMV from normal in speech-relevant regions: the left inferior frontal gyrus and bilateral temporal regions. Reduced FA was found in the left white matter tracts underlying the motor regions for face and larynx in the persistent stuttering group. Contrary to previous findings in adults who stutter, no increases were found in the right hemisphere speech regions in stuttering or recovered children and no differences in right-left asymmetries. Instead, a risk for childhood stuttering was associated with deficiencies in left gray matter volume while reduced white matter integrity in the left hemisphere speech system was associated with persistent stuttering. Anatomical increases in right hemisphere structures previously found in adults who stutter may have resulted from a lifetime of stuttering. These findings point to the importance of considering the role of neuroplasticity during development when studying persistent forms of developmental disorders in adults.

Figure 1

Statistical parametric maps of the Z statistic overlaid on an averaged brain based on all subjects (statistical maps thresholded at p<.001 (uncorrected)). Images are displayed in neurological convention. A. Areas where the control group exhibited significantly more GMV compared to the stuttering group. B. Areas where the persistent group exhibited significantly less GMV compared to control group. C. Areas where the recovered group exhibited significantly less GMV compared to the control group.

Figure 2

Statistical parametric maps of the Z statistic overlaid on an averaged brain based on all subjects (statistical maps thresholded at p<.001 (uncorrected)). Images are displayed in neurological convention. A. Areas where the recovered group exhibited significantly more GMV compared to the persistent stuttering group. B. Areas where the persistent group exhibited significantly more GMV compared to recovered group.

Figure 3

Bar graphs of the mean gray matter volumes (GMV) and standard errors for left Brodmann’s area 44 (LBA44) and left Brodmann’s area 45 (LB45), the left superior temporal gyrus (LSTG) and the right STG sides in all three groups, the fluent controls (white bars), the persistent stuttering children (hatched bars) and the recovered children (solid black bars).

Figure 4

Scatterplots of the relationships within each group (fluent controls (CONTROL), recovered (RECOVERED), persistent (PERSISTENT) stuttering children) of their gray matter volume (GMV) for four structure combinations (the left Brodmann’s area 44 (LBA44) and left Brodmann’s area 45 (LB45), the left Brodmann’s area 45 (LB45), the left superior temporal gyrus (LSTG), the right and left STG, and the right and left supramarginal gyrus (SMG)). The r values are Pearson Correlation Coefficients relating each subjects’ GMV values in each of the two structure pairs.

Figure 5

Areas where normally fluent children exhibited significantly higher FA values compared to stuttering children (persistent and recovered) are shown in red overlaid on the mean FA skeleton (green) and the mean FA map. Z values were thresholded at an uncorrected p<.001.

Figure 6

Bar graph of group mean FA values and standard errors for the white matter tract underlying the Rolandic Operculum on the left and right sides in all three groups, the fluent controls (white bars), the persistent stuttering children (hatched bars) and the recovered children (solid black bars).