Frontal Lobe
The medial surface presents the following:
- part of the frontopolar gyri
- part of the superior frontal gyrus
- part of the paracentral lobule
The medial surface is crossed by the callosal sulcus and the cingulate sulcus.
Medial surface of the frontal lobe
Rostral sulcus
The fissure on the medial surface of the frontal lobe located between the medial surface of the inferior frontopolar gyrus, the straight gyrus, and the rostral gyrus. The ventral portion of the groove is further divided into two segments, the superior and the inferior rostral sulci.
Rostral gyrus
The gyrus on the medial surface of the frontal lobe placed between the inferior portion of the cingulate sulcus and the rostral sulcus. Posteriorly, the limit is the anterior paraolfactory sulcus which separates it from the subcallosal area. Anteriorly, it continues as the inferior frontopolar gyrus which forms the frontal pole. It can be further divide in two portions: the superior and inferior Rostral gyri.
Anterior paraolfactory sulcus
The vertical groove on the medial surface of the frontal lobe limiting the subcallosal area anteriorly.
Posterior paraolfactory sulcus
The vertical groove on the medial surface of the frontal lobe separating the subcallosal area from the paraterminal gyrus.
Central region
Paracentral sulcus
The fissure on the medial surface of the cerebrum located anterior to the paracentral lobule. It is anterior to the precentral sulcus, delimiting the medial surface of the superior frontal gyrus. Occasionally it is a continuation of the precentral sulcus.
Paracentral lobule
The area extending on the medial surface of the hemisphere connecting the superior portion of the precentral gyrus to the post central gyrus. Anteriorly, the medial surface of the superior frontal gyrus is separated from it by the paracentral sulcus. Inferiorly, the cingulate gyrus is separated from it by the posterior segment of the cingulate sulcus. Posteriorly, the limit is represented by the marginal ramus, which separates it from the cuneus.
Parietal Lobe
The medial surface of the hemisphere presents the medial expansion of the superior parietal lobule, superiorly, called the precuneus. It also includes the posterior part of the paracentral lobule and part of the cingulate gyrus.
Precuneus
The portion of the medial surface of the parietal lobe placed above the postero-superior portion of the corpus callosum. It is located posterior to the paracentral lobule and the post central gyrus, and anterior to the cuneus. Precuneus, also called quadrate lobe or quadrangular lobule of Foville, it is a medial subdivision of the parietal lobe placed on the posterior superior of the corpus callosum.
On the anterior surface, the ascending ramus (also called marginal portion) of the cingulate sulcus separates it from the paracentral lobule and the post central gyrus. On the inferior surface, the sub parietal sulcus separates it from the posterior portion of the cingulate gyrus. Posteriorly, it is divided from the cuneus by the parietal occipital sulcus. It can be regarded as a mesial expansion of the superior parietal lobule.
Occipital Lobe
The medial surface presents two sulci: the parieto-occipital sulcus and the calcarine sulcus; they limit a gyrus called the cuneus. Below the calcarine sulcus, there is the lingual gyrus, projecting towards the temporal lobe. Between the lingual and the fusiform gyri, the collateral sulcus can be identified.
Cuneus
The gyrus on the medial surface of the occipital lobe. Anteriorly, it is separated from the precuneus by the parieto-occipital sulcus; inferiorly from the lingula by the calcarine sulcus. Laterally, it is limited by the superior occipital gyrus. The superior and inferior sagittal sulci can be present on the surface of the cuneus, running parallel to the calcarine sulcus.
Calcarine sulcus
The sulcus that originates at the level of the parahippocampal gyrus and the splenium of the corpus callosum. It extends posteriorly ending at the occipital pole. It divides the inferior portion of the cuneus from the lingual gyrus.
The anterior segment of the calcarine sulcus, known as anterior calcarine sulcus, crosses the inferior segment of the parietal occipital sulcus forming a prominence on the medial wall of the occipital horn of the lateral ventricle, called the calcar avis. The caudal portion of the calcarine sulcus on the surface of the occipital lobe. Posteriorly it limits the gyrus descendent of Ecker, running parallel to the occipito-polar sulcus. Usually, it is possible to recognize a T- or Y-shape pattern.
Calcar avis
The prominence on the medial wall of the occipital horn of the lateral ventricle located where the anterior segment of the calcarine sulcus crosses the inferior one of the parieto-occipital sulcus. At this level, the temporal horn of the lateral ventricle continues into the occipital horn.
Lingual gyrus
The tongue-like shaped gyrus on the basal surface of the occipital and temporal lobes. Superiorly, it is limited by the cuneus; anteriorly, it continues into the parahippocampal gyrus. Laterally, it is bounded by the occipital temporal gyrus. On the inferior surface, it can be divided into a superior and an inferior lingual gyrus by the lingual sulcus.
Occipito-polar sulcus
The small fissure parallel to the retrocalcarine sulcus that borders the gyrus descendent of Ecker anteriorly.
Gyrus descendent of Ecker
The gyrus located between the retrocalcarine and the occipito-polar sulcus.
Other Structures
Lamina terminalis
The anterior wall of the third ventricle, located below the rostrum of the corpus callosum and above the optic chiasm, between the frontal lobes at the level of the interhemispheric fissure.
Paraterminal gyrus
The small gyrus of the limbic lobe located in front of the lamina terminals and third ventricle. On the anterior surface, the posterior paraolfactory sulcus divides it from the subcallosal area. It is continuous with the indusium griseum.
Subcallosal gyrus
The area situated on the inferior surface of the rostrum and in front of the lamina terminalis, between the anterior paraolfactory and the posterior paraolfactory sulci, also known as subcallosal area. On its inferior surface, the olfactory striae and the anterior perforated substance are placed. It is a continuation of the rostral gyrus and the anterior portion of the cingulate cortex.
Corpus callosum
The main connection between the two hemispheres. It is constituted by white matter fibers connecting each lobe of the hemisphere with the contralateral one.
It is further subdivided into the following parts, from anterior to posterior: rostrum (blue), genu (green), body (orange), splenium (purple).
Cingulate sulcus
The main fissure on the medial surface of the cortex. It starts at the level of the rostrum, anteriorly to the subcallosal area, running parallel to the corpus callosum. It ends at the level of the splenium. It is possible to recognize different portions: inferior, anterior, and posterior. Numerous sulci originate from the main groove, sometimes an intracingulate sulcus can be identified.
The caudal segment has a vertical ramus, called ascending or marginal ramus, which separates the posterior surface of the paracentral lobule from the anterior surface of the precuneus.
Cingulate gyrus
The convolution on the medial surface of the hemisphere belonging to the limbic lobe. It embraces the corpus callosum arising at the level of the rostrum, anteriorly to the subcallosal area, separated from the frontal and a portion of the parietal lobe by the cingulate sulcus.
The subparietal sulcus divides the posterior part from the medial surface of the parietal lobe. It ends at the level of the splenium of the corpus callosum. It is composed of three portions: anterior, anterior midcingulate, posterior midcingulate, and isthmus or posterior cortex of the cingulate gyrus. Anteriorly, the rostral portion may be a continuation of the subcallosal area; posteriorly, the isthmus continues to the parahippocampal gyrus.
Isthmus (ICgG)
Caudal portion of the cingulate cortex located at the level of the splenium. it connects the cingulate gyrus to the parahippocampal gyrus. Occasionally the anterior portion of the calcarine sulcus splits it from the parahippocampal gyrus and the lingual gyrus.
Pineal gland
The endocrine gland extending posteriorly from the posterior wall of the third ventricle, between the occipital lobes and the two pulvinars of the thalami. It is located below the splenium of the corpus callosum and above the quadrigeminal plate of the midbrain. It produces Melatonin and is involved in sleep-wake cycles.
Subparietal sulcus (SS) or (sbps)
Groove of the medial surface of the hemisphere, located between the inferior surface of the precuneus and the caudal portion of the cingulate gyrus; it is the continuation of the cingulate sulcus posteriorly. It is characterized by different patterns: H, oblique, single or triple upward branch and double horizontal sulci pattern.
