Asymmetry of the lateral (sylvian) fissures in man.

We compared the courses of right and left lateral (sylvian) fissures by superimposing left lateral and reversed right lateral photographic slide projections and tracing the sulci and fissures of each hemisphere in different colors. A characteristic pattern of divergence of posterior regions of the lateral fissures was noted in 25 of 36 adult brains. After pursuing similar courses, the right lateral fissure angulates sharply upward into the inferior parietal area while the left one continues posteriorly. As a consequence, on the right, there is a smaller parietal operculum, a shorter planum temporale, a higher sylvian point, and compensatory expansion of the inferior parietal region posterior to the lateral fissure.