Structural and functional brain asymmetries in human situs inversus totalis

Objective: To determine whether individuals with situs inversus totalis CSI ), a condition in which there is a mirror-image reversal of asymmetric visc eral organs, have alterations in brain asymmetries. Background: The human b rain is asymmetric in structure and function. Although correlations between anatomic asymmetries and functional lateralization in human brain have bee n demonstrated, it has been difficult tu further analyze them. Characteriza tion of asymmetries of brain structure and function in SI might advance the understanding of these relationships. Methods: Using anatomic and function al MRI techniques, we analyzed asymmetries in the brains of three individua ls with SI. Results: Two major anatomic asymmetries of the cerebral hemisph eres, the frontal and occipital petalia, were reversed in individuals with SI. In contrast, SI subjects had left cerebral hemisphere language dominanc e on functional MRI analysis as well as strong right=handedness. Conclusion : These observations suggest that the developmental factors determining ana tomic asymmetry of the cerebral petalia and viscera are distinct from those producing the functional lateralization of language.