Anomalous anatomy of speech-language areas in adults with persistent developmental stuttering

The major aim of this study was to determine whether adults with persistent developmental stuttering (PDS) have anomalous anatomy in cortical speech-language areas. The major postulate was that anomalous cerebral dominance, reflected by anomalous cortical anatomy in various regions, may put an individual at increased risk for the development of stuttering.

Adults with PDS (n = 16) and controls (n = 16) matched for age, sex, hand preference, and education were studied. Volumetric MRI scans were completed. Frontal (pars triangularis, pars opercularis) and temporo-parietal areas (planum temporale, posterior ascending ramus) were measured in the left and right hemispheres and interhemispheric asymmetries were computed. Gyral variants were assessed within these perisylvian cortical speech-language areas.

The right and left planum temporale were significantly larger in the adults with PDS (p = 0.045), and the magnitude of the planar asymmetry was reduced (p = 0.003). Some gyral variants were unique to the adults with PDS, including a second diagonal sulcus and extra gyri along the superior bank of the sylvian fossa. In addition, anatomic subgroups emerged based on sex and hand preference. Overall, the adults with PDS had significantly more gyral variants (mean = 4.19) than controls (mean = 1.31, p < 0.0005).

These results provide strong evidence that adults with PDS have anomalous anatomy in perisylvian speech and language areas. No one anatomic feature distinguished the groups, but multiple loci within a widely distributed neural network differed between groups. These results provide the first evidence that anatomic anomalies within perisylvian speech-language areas may put an individual at risk for the development of stuttering.