Sylvian fissure

Last revised by Dr Daniel MacManus on 27 Mar 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 inferiorly3. The insular cortex is located immediately deep to the Sylvian fissure. 

Gross anatomy

The Sylvian fissure can be divided into a superficial and deep part. The superficial part comprises the sylvian fissure 'stem' and three main rami (anterior horizontal, anterior ascending, and posterior rami). The deep part comprises two compartments called the sphenoidal and the operculoinsular compartments of the sylvian fissure3.

From its origin lateral to the anterior perforated substance, the fissure courses medially to form the stem of the lateral fissure, also known as the Sylvian cistern, into which passes the middle cerebral artery and its major branches. Laterally, it has two branches or 'rami' which extend into, and divide, the frontal operculum

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

The lateral sulcus terminates posteriorly in a bifurcation, with the posterior ascending ramus lying within the supramarginal gyrus of the inferior parietal lobule.

Superiorly the lateral sulcus may be termed the circular sulcus, surrounding the insular cortex medially.

The operculoinsular compartment of the sylvian fissure can be further subdived into an opercular and insular compartments. The more medial insular compartment is located on the lateral surface of the insula and contains the M2 segment of middle cerebral artery (MCA) and insular veins. 

The opercular compartment is located between the opercula laterally. It is the location of the M3 segment of the MCA once the M2 segment completes its downward 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 cortex3.

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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