Sylvian fissure
Sylvian fissure is the most consistent anatomical landmark. It is located on the superolateral surface of the hemisphere and separates frontal and temporal lobe, it is also called the lateral sulcus or lateral fissure.
Anterior Sylvian point divides the Sylvian fissure in into two rami:
- the anterior ramus
- the posterior ramus
The Sylvian fissure is often exposed through the pterional approach. The dissection of this fissure allows reaching the MCA, carotid artery, optic nerve, etc.
Parts of the Sylvian fissure
Anterior ramus of the Sylvian fissure
It is formed by the anterior horizontal /green/ and the anterior ascending /or vertical = purple/ rami, placed at the level of the squamous suture. These rami divide the inferior frontal gyrus into three parts – pars orbitalis, pars triangularis and pars opercularis.
Posterior ramus of the Sylvian fissure
It is the longest and runs towards the inferior surface of the parietal lobe, where the supramarginal gyrus surrounds its posterior end.
Central sulcus
The fissure separating the frontal lobe from the parietal lobe, also called Rolandic fissure. It arises from the superior limit of the hemisphere and slides on the lateral surface following a flexuous course.
The final segment does not often cross the Sylvian fissure but intersects the superior segment of the circular sulcus of the insula. It is usually located 2–5 cm behind the coronal suture, and it can be divided in two anterior and posterior rami.
It is characterized by three curves. The superior and inferior curves shape an anteriorly directed convexity, whereas the middle curve forms a concavity.
Parietooccipital sulcus
The vertical sulcus on the medial surface of the hemisphere dividing the parietal lobe from the occipital lobe (on the medial surface – the precuneus from the cuneus). It arises from the cuneate sulcus, delimiting the cuneus anteriorly and the precuneus posteriorly.
It runs behind the level of the splenium and may present numerous patterns: T- or Y-shape, straight, or ramified into more branches.
Preoccipital notch
The small fissure, also known as temporo-occipital incisure, that constitute the limit between the temporal and occipital lobes.
Relationship between main sulci/fissures and the lobes
Interhemispheric fissure
The fissure separating the two hemispheres of the telencephalon. It extends around the connections between the two hemispheres, constituted by the corpus callosum and the structures of the diencephalon.
