Hemispheric and sex-linked differences in Sylvian fissure morphology: A quantitative approach using volumetric magnetic resonance imaging

Objective: In a sample of right-handed adults, volumetric magnetic resonanc e imaging (MRI) was used to reinvestigate hemispheric and sex-linked differ ences in Sylvian fissure (SF) morphology. Background: Asymmetries of the SF exist with a predominant leftward asymmetry consistently reported in postm ortem studies. These anatomic asymmetries may reflect asymmetric allocation of adjacent opercula, with some investigators positing a relationship with planum temporale asymmetries, as the postcentral SF is more asymmetric tha n the anterior segment. Sex-related differences have also been reported wit h reduced asymmetries in women relative to men. Method: Using in vivo MRI s urface renderings, SF asymmetries were studied in a group of consistently r ight-handed men (n = 12) and women (n = 12). Anterior and postcentral SF le ngths were measured. Results: Overall, there was a significant leftward asy mmetry of the horizontal SF (anterior and postcentral) in men and women. Wh ereas there was a significant leftward asymmetry of the postcentral SF, the re was no significant asymmetry of the anterior SF. There was an increase i n the parietal operculum anterior to the posterior ascending ramus (PAR) in the left hemisphere and posterior to the PAR in the right hemisphere when SF asymmetries were leftward, with the length of the anterior parietal oper culum positively correlated with postcentral SF length. Conclusions: These findings demonstrate that the SF is asymmetric but that clear sex-related e ffects do not exist in consistently right handed subjects.