Sylvian fissure

Last revised by Francis Deng on 28 Nov 2021

The Sylvian fissure, also known as the lateral sulcus or fissure, begins near the basal forebrain and extends to the lateral surface of the brain separating the frontal and parietal lobes superiorly from the temporal lobe inferiorly 3. The insula is located immediately deep to the Sylvian fissure. 

Gross anatomy

The Sylvian fissure can be divided into superficial and deep portions 3,4. The superficial portion comprises the Sylvian fissure stem and three rami (anterior horizontal, anterior ascending, and posterior rami). The deep portion, also known as the Sylvian cistern, comprises an anterior part called the sphenoidal compartment and a posterior part called the operculoinsular compartment 5.

The stem of the superficial Sylvian fissure begins at the anterior clinoid process and curves along the sphenoid ridge. Laterally, it originates two anterior rami that extend into, and divide, the frontal operculum, and continues as the posterior ramus. 

The anterior ramus (also known as horizontal ramus) separates the pars orbitalis from the pars triangularis. The ascending ramus (also known as vertical ramus or anterior ascending ramus) separates the pars triangularis from the pars opercularis

The posterior ramus is the longest of the superficial Sylvian fissure, extending from the pterion to its termination wrapped by the supramarginal gyrus of the inferior parietal lobule 4.

The sphenoidal compartment of the Sylvian fissure is the narrow space between the frontal and temporal lobes, contiguous with the carotid cistern, that passes the M1 segment of the middle cerebral artery until it turns at the limen insulae.

The operculoinsular compartment of the Sylvian fissure proceeds posterior to the limen insulae and can be further subdivided into opercular and insular clefts 4. The more medial insular cleft is located on the lateral surface of the insula and contains the M2 segment of middle cerebral artery and insular veins. The superior limb of the insular cleft separates the insula from the medial surface of the frontoparietal operculum, while the inferior limb of the insular cleft separates the insula from the medial surface of the temporal operculum. The insular cleft terminates as the circular sulcus or limiting sulcus, which surrounds the insular cortex.

The opercular cleft is located between the opercula laterally. It is the location of the M3 segment of the middle cerebral artery once the M2 segment completes its turn at the superior and inferior limiting sulci of the insula to follow the inner surface of the frontal, parietal, and temporal opercula towards the outer surface 3.

History and etymology

The Sylvian fissure is named for Franciscus Sylvius (1614-1672), German/Dutch physician and anatomist, who described it as the "fissura cerebri lateralis Sylvii" 2.

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Cases and figures

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