What Are Sylvian Fissures in the Brain?

The Sylvian fissure in the brain refers to a groove located near the base and along the sides of the brain that separates the higher frontal and parietal lobes from the lower temporal lobe. Interchangeable terms for the Sylvian fissure include the lateral fissure and lateral sulcus.

On each frontal side of the brain, the Sylvian fissure begins at the base and surface and extends diagonally upwards to separate the upper and lower areas. It is one of two major fissures in the brain, with the other being the central sulcus. The main portion of the fissure may be joined at its beginning and end, with one or several different additional branches also known as rami.

The actual width and length of the fissure varies from person to person and can differ from side to side of the brain in the same individual. It is more often than not longer on the left side of the brain than the right. Its anatomical structure holds significance in surgical planning and outcomes.

The Sylvian fissure also houses a secondary lobe of the brain, the insular lobe. Above, the Sylvian fissure is bordered by the inferior frontal gyrus in the frontal lobe and the post central gyrus in the parietal lobe. Below, the fissure meets the superior temporal gyrus in the temporal lobe.