Neurological

Stuttering associated with increased iron in the basal ganglia

Patients who stutter have increased R2 * in the left putamen and associated frontal cortical regions, likely reflecting increased iron levels compared to people who do not stutter, according to study results published in Brain.

The researchers found that there was strong theoretical evidence that basal ganglia dysfunction is linked to developmental stuttering. This theory stems from the observed common motor characteristics of Parkinson’s and dystonia – basal ganglia disorders – along with changes in speech flow associated with dopaminergic drugs or deep brain stimulation. However, there is currently no imaging evidence to support or disprove this theory.

The aim of the current study was to scan the brains of people who stutter and, using multiparameter mapping, to compare them with age- and gender-adjusted people who do not stutter. This mapping generates semiquantitative whole-brain maps of R1, MTsat and R2 *. Stuttering severity was assessed using the Stuttering Severity Instrument-Fourth Edition.

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The analysis was based on multi-parameter maps from 73 participants – 41 people who stutter (median age 31.2 years; 9 women) and 32 people who typically speak fluently (median 28.6 years; 9 women). Participants who stuttered and those who were fluent did not differ in total brain volume or the values ​​averaged across all voxels in the gray and white tissue maps of R1, MTsat, and R2 *.

In the whole-brain voxel-wise analysis of the quantitative maps, a significantly higher R2 * gray matter was observed in participants who stuttered than in subjects who were generally fluid subcortically in the left putamen and cortically mainly in the left frontal lobe, including the frontalopercular cortex, the extends to the front island; the inferior frontal gyrus (pars opercularis) and the posterior extent of the inferior frontal sulcus; and ventral precentral gyrus corresponding to the level of representation of tongue movements.

Voxel peak values ​​at points with increased R2 * in stuttering persons included the left temporal planum (P = 0.025), the left precentral gyrus (ventral) (P = 0.024) and the left lower frontal gyrus, pars opercularis (P =. 024).

At this threshold (P <.025) the group differences were limited to the left hemisphere. At a lower threshold (P <.05), group differences were also found in the left caudate nucleus subcortically and larger parts of the right and left hemispheres cortically.

A significant linear increase in R2 * with age was found in all regions, but this did not differ between the two groups of participants.

“Our results provide evidence of microstructural differences in stutterers that is consistent with theoretical reports of developmental stuttering that imply dysfunction of the corticobasal ganglia-thalamocortical loops through the putamen,” the researchers explained. “More work is needed to relate R2 * differences to genetic profiles associated with developmental stuttering, with increased dopamine or lysosomal dysfunction, or with any other neurobiological function that could indicate effective therapies for those who want it. “

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Cler GJ, Krishnan S, Papp D, Wiltshire CEE, Chesters J, Watkins KE. Increased iron concentration in the putamen and in the cortical speech motor network in developmental stuttering. Brain. Published online on November 9, 2021. doi: 10.1093 / brain / awab283

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