ANOMALOUS CEREBRAL STRUCTURE IN DYSLEXIA REVEALED WITH MAGNETIC-RESONANCE-IMAGING

Objective.-To develop quantitative methods for identifying cerebral an omalies on magnetic resonance images of subjects with language disorde rs and other learning disabilities. Design.-Partially blinded comparis on of subjects with dyslexia, unaffected relatives, and a control grou p balanced for age and socioeconomic status. Criterion standard: clini cal diagnosis of dyslexia by physician or learning disabilities specia list on the basis of clinical assessment and family history. Settings. -Hospital pediatric neurology clinic and private reading clinic. Patie nts and Other Participants.-Volunteers: individuals with dyslexia (sev en male and two female,aged 15 to 65 years) from professional families ; unaffected first- and second-degree relatives (four male and six fem ale, aged 6 to 63 years) available in the geographical area; and contr ols (five male and seven female, aged 14 to 52 years). Interventions.- Gradient echo three-dimensional scan in Seimens 1-Tesla Magnetom; 128 1.25-mm consecutive sagittal images. Main Outcome Measures.-41) Averag e length of the temporal (T) and parietal (P) banks of the planum temp orale; (2) interhemispheric coefficients of asymmetry for T and P bank s: Left-Right interhemispheric coefficients of asymmetry=(L-R)/[(L+R)/ 2]; (3) intrahemispheric coefficients of asymmetry=(T-P)/[(T+P)/2]; an d (4) qualitative assessment of gyral variants in the parietotemporal operculum. Results.-All groups had left-sided asymmetry for the tempor al bank and right-sided asymmetry for the parietal bank. The group wit h dyslexia had exaggerated asymmetries, owing to a significant shift o f right planar tissue from the temporal to parietal bank. They also ha d a higher incidence of cerebral anomalies bilaterally (subjects with dyslexia, six of nine; relatives, two of 10; and controls, zero of 12) . Conclusions.-Quantitative assessment of high-resolution magnetic res onance images can reveal functionally relevant variations and anomalie s in cerebral structure. Further refinement of these measurement techn iques should improve the diagnosis, classification, and treatment of l anguage disorders and other learning disabilities.