| Summary: | Current methods of diagnosis for developmental dyslexia rely on family history report and cognitive and language behavioral testing. However, relying on these measures alone to predict dyslexia in at-risk children can result in low sensitivity and specificity, with dyslexic individuals either being missed or over-identified. Prediction accuracy could be increased by considering structural differences in the dyslexic brain along with behavioral measures. Reduplication of Heschl’s gyrus, where the primary auditory cortex resides, has been suggested as a risk factor for developing dyslexia. The current investigation explored if differences in interhemispheric duplication patterns and gray matter volume of Heschl’s gyrus could distinguish between dyslexic and neurotypical (control) brains. A detailed labeling protocol based on macroanatomical landmarks and explicitly defined reduplication morphotypes: single Heschl’s gyrus (SH), common stem duplication (CSD), complete posterior duplication (CPD), and multiple duplication (MD) was developed. Overall, there was no significant difference in the incidence of morphotypes between control and dyslexic brains. Duplication of Heschl’s gyrus was a common occurrence in both groups. However, results suggest that the MD morphotype may occur more often in dyslexic brains. Gray matter volume of anterior Heschl’s gyrus was larger in the left hemisphere in both groups but tended to be larger overall in dyslexic brain. Results of this investigation confirmed the presence of high morphological variability between and within brains and suggest that reduplications in Heschl’s gyrus alone are not enough to designate between neurotypical and dyslexic brains. It is likely that developmental dyslexia has heterogeneous origins, and it is possible that increased gyrification combined with other structural differences is one possible origin.
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