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 resonance imaging (MRI) was used to reinvestigate hemispheric and sex-linked differences in Sylvian fissure (SF) morphology. Background: Asymmetries of the SF exist with a predominant leftward asymmetry consistently reported in postmortem 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 than the anterior segment. Sex-related differences have also been reported with reduced asymmetries in women relative to men. Method: Using in vivo MRI surface renderings, SF asymmetries were studied in a group of consistently right-handed men (n = 12) and women (n = 12). Anterior and postcentral SF lengths were measured. Results: Overall, there was a significant leftward asymmetry of the horizontal SF (anterior and postcentral) in men and women. Whereas there was a significant leftward asymmetry of the postcentral SF, there was no significant asymmetry of the anterior SF. There was an increase in 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 operculum positively correlated with postcentral SF length. Conclusions: These findings demonstrate that the SF is asymmetric but that clear sex-related effects do not exist in consistently right-handed subjects.