How to delineate the different parts of the temporal lobe looking on a 3D MRI ? G.Salamon M.D. Neuroradiology LONI UCLA.

Principles: To be oriented with left and right sides always in the same position during your analysis. The same rule for the anterior or the posterior parts of the brain Have a good orientation with the help of a 3D analysis. Remember that there is in normal cases an asymmetry of some sulci on left or right hemisphere. This is visible at the level of the sylvian fissure, of the central sulcus, of the interparietal sulcus. Be familiar with the main division of the brain in relation with the existence of brain sulci or brain fissures. Have a knowledge of some variations concerning the course or even the number of some sulci (duplication). Try as often as it is possible to verify your labeling with color not only in one single plane but on another orthogonal one: for ex. sagittal and coronal, coronal and horizontal … Start to define some sulci which will give a very clear delineation during your study of the rest of the brain: sylvian fissure, cingulate sulcus for ex.. 2

Orientation Anterior frontal Anterior temporal Posterior occipital Superior frontal Superior parietal Left hemisphere after dissection Brodman’s area of external part of the brain Brain arteries after injection on sagittal section White matter tracts with DTI Inferior temporal 3

Orientation and planes of section on MRI Horizontal section Coronal section Sagittal section Anterior frontal Posterior occipital Superior frontal External temporal Medial or internal Medial or internal or interhemispheric External temporal Inferior temporal Superior parietal 4

Great division of the brain hemispheres Frontal lobe Temporal lobe Parietal lobe Occipital lobe Limbic lobe cingulate gyrus Limbic lobe. Para hippocampal gyrus Occipital lobe Temporal lobe Parietal lobe Frontal lobe The different number correspond to the division proposed by Brodman Anterior Inferior Posterior Superior Inferior External view of the brain Internal view of the brain 5

Sylvian fissure- Post central sulcus posterior limit of primary sensory area in parietal lobe Gyrus supra marginalis ( parietal lobe) Wernicke’s area belongs to superior temporal gyrus Superior temporal gyrus Superior temporal sulcus Inferior temporal sulcus Middle temporal gyrus Inferior temporal gyrus Terminal branch sylvian fissure External part of the temporal lobe on a dissected brain With a blue arrow: gyrus With a red arrow: sulcus Heschl’s gyrus external part of primary auditive area Central sulcus limit between frontal and parietal lobe and posterior limit of primary motor area 6

Inferior part of the temporal lobe on a dissected brain Temporal pole Temporo occipital sulcus Collateral sulcus Rhinal sulcus Para hippocampal gyrus Lingual gyrus Fusiform gyrus Inferior temporal gyrus With a blue arrow: gyrus With a red arrow: sulcus 7

Great division of the temporal lobe Different parts of the temporal lobe are superior, external and inferior: Superior part of the temporal lobe with a transverse gyrus is called transverse gyrus of Heschl. It corresponds to the primary auditive area. The Heschl’s gyrus is in the depth of the Sylvian fissure and only its most external part is visible on a dissection. It is clearly delineated when looking on an horizontal MRI. Back to the transverse gyrus on the superior aspect of the temporal lobe is an area called the planum temporal. It is also in the depth of the sylvian fissure. At the external part of the brain there are three temporal gyri, superior, middle and inferior separated by a superior and an inferior temporal sulcus. The third surface of the temporal lobe is inferior. On the inferior surface two main sulci divide this part of the temporal lobe. The lateral temporo occipital sulcus is the limit between the inferior temporal gyrus with the fusiform gyrus.The collateral sulcus is the limit between the fusiform gyrus and a more medial one called at the temporal lobe level the parahippocampal gyrus and posteriorly in the occipital lobe the lingual gyrus. The anterior part of the collateral sulcus ends medially and is called rhinal sulcus. The part of the temporal lobe inside the choroid fissure belongs to the limbic lobe. It is called at this level the hippocampus. 8

Superior part of the temporal lobe The superior part of the temporal lobe correponds to the part located in the depth of the sylvian fissure. The main part of this aspect is the transverse temporal gyrus, described by Heschl. It receives the acoustic radiations and corresponds to the primary auditive area. Around this area at the external part of the brain the posterior part of the superior temporal gyrus is called the Wernicke’s area. At this level a lesion on the dominant hemisphere may determine an aphasia, aphasia of sensory type. The patient has no important trouble for elocution but his comprehension is totally reduced and his language has no sense even if the words prononced are correct. Posteriorly located on the superior part of the temporal lobe the area is called the planum temporal. It is larger on the dominant hemisphere. Norman Geshwin, who analyzed this area, got the idea that such assymetry was in relation with the importance of the cortical area devoted to language functions. 9

MRI on horizontal plane of the temporal lobe Heschl’s gyrus Insula Sylvian fissure anterior part Collateral fissure Lingual gyrus belongs to the temporo occipital area Planum 10

External part of the temporal lobe The sylvian fissure, the superior temporal sulcus and the inferior temporal sulcus have an horizontal direction. For this reason the best plane of examination on MRI will be the coronal plane. Nevertheless try always to correlate your delineation on the coronal plane with sagittal section or external view. The horizontal images on MRI are the most difficult for an accurate analysis. It is important to delineate as exactly as possible the terminal part of the sylvian fissure on the two sides. It is admitted that due to anatomic variations in relation with language the sylvian fissure ends on the right side at a straight angle while on the left its termination is a little more posterior and oriented more horizontally. Right hemisphere Left hemisphere 11

MRI on coronal plane of the temporal lobe With a blue caption: gyrus With a red caption: sulcus Sylvian fissure Sup. temporal sulcus Inf.temporal sulcus Occipito temporal sulcus Collateral sulcus Choroidal fissure Sup. temporal gyr. Middle temp.gyr. Inferior temporal gyrus or occipito temporal lateral gyrus Fusiform gyrus Para hippocampal posteriorly named lingual Hippocampus or Ammon horn ( belongs to limbic lobe) 12

Sylvian fissure Superior temporal sulcus Inferior temporal sulcus Tempo-occipital sulcusCollateral sulcus Hippocampus (limbic lobe) Heschl’s gyrus Sup.temp.gyrus Middle temporal gyrus Inf. temporal gyrus Para hippocampal gyrus Fusiform gyrus MRI on Coronal view of temporal lobe at the level of midpart of hippocampus 13

MRI on coronal plane of the temporal lobe This section is more anterior than the two preceeding ones With a blue caption: gyrus With a red caption: sulcus Para hippocampal gyrus Fusiform gyrus Inferior temporal gyrus Middle temp.gyr. Sup. temporal gyr. Hippocampus (limbic lobe) Amygdaloid nucleus (limbic lobe or deep brain nuclei) Sylvian fissure Sup. temporal sulcus Inf.temporal sulcus Occipito temporal sulcus Collateral sulcus 14

Amygdaloid nucleus Fusiform gyrus Inferior temporal gyrus Middle temporal gyrus Superior temporal gyrus Sylvian fissure Superior temporal sulcus Tempo-occipital sulcus Inferior temporal sulcus Entorhinal sulcus Insula Coronal view of temporal lobe at the level of amygdaloid nucleus The entorhinal sulcus is the anterior terminal part of the collateral sulcus 15

Sylvian fissure Superior temporal sulcus Inferior temporal sulcus Superior temporal gyrus Middle temporal gyrus Inferior temporal gyrus Temporo occipital sulcus MRI on coronal plane at the anterior temporal lobe level : temporal pole At this level there is no fusiform or parahippocampal gyrus. The three gyri which contribute to the formation of the temporal pole are the superior, middle and inferior ones 16

Sylvian fissure Superior temporal sulcus Inferior temporal sulcus Superior temporal gyrus Middle temporal gyrus Inferior temporal gyrus Supra marginal gyrus (parietal lobe) Angular gyrus (parietal lobe) MRI on sagittal plane of the temporal lobe On some text books supra marginal gyrus belongs to the parietal lobe and to the temporal lobe. For a simple classification the part of supra marginal gyrus below the sylvian fissure may be related to the superior temporal gyrus Wernicke’s area 17

MRI on inferior plane of the temporal lobe The inferior part of the temporal lobe has no real limitation with the corresponding area of the occipital lobe. The posterior part of the temporal lobe is often considered as temporo occipital. Nevertheless a demarcacation can be proposed with a line perpendicular to the antero inferior part of the parieto occipital fissure where this fissure is common with the calcarine one. Posteriorly the collateral fissure is the main demarcation between the lingual gyrus and the fusiform one. More anteriorly the same collateral fissure separates the parahippocampal gyrus from the fusiform gyrus. When the collateral fissure ends at the level of the entorhinal sulcus the inferior temporal lobe is mainly formed by the inferior temporal gyrus The red line corresponds to the commissural plane. The small arrow corresponds to the most anterior part of the calcarine fissure where it joins the parieto occipital one. The plane (in blue) at this level could be considered as the formal limit between the temporal and the occipital lobe on horizontal MRI. 18

MRI on horizontal plane of the temporal lobe With a blue caption: gyrus With a red caption: sulcus Collateral sulcus Fusiform gyrus Lingual gyrus Amygdaloid nucleus Para hippocampal gyrus Temporal pole Entorhinal sulcus 19

Lingual gyrus and fusiform gyrus belong to the temporo occipital area Collateral sulcus Ento rhinal sulcus Temporal pole Amygdaloid nucleus Arbitrary delineation between parahippocampal gyrus and lingual gyrus Parahippocampal gyrus Lingual gyrus Fusiform gyrus Midbrain MRI on horizontal plane of the temporal lobe The course of the collateral sulcus may be interrupted in some part of its course 20

Temporal lobe: superior aspect, planum, Heschl’s gyrus Sylvian fissure Superior temporal sulcus Planum temporal Heschl’s gyrus transverse temporal gyrus, primary auditive area Sylvian fissure Heschl’s gyrus Heschl’s gyrus transverse temporal gyrus, primary auditive area Insular cortex Sylvian fissure Superior temporal sulcus Orientation of the main temporal sulci on 3D imaging 21

Temporal lobe: external aspect, superior, middle temp. gyrus Inf. temporal sulcus Sup. temporal sulcus Sylvian fissure Sup. temporal sulcus Inf. temporal sulcus Sup. temporal gyrus Middle temporal gyrus Sup. temporal gyrus Middle temporal gyrus Inf. temp. gyrus Middle temporal gyrus Sup. temporal gyrus Sup. temp gyrus Orientation of the main temporal sulci on 3D imaging 22

Temporal lobe: infero- external aspect, occip.temp. sulcus SMG Middle temp. gyrus Occ. temp.FusiformLingual Sup.temporal gyrus Middle temp. gyrus Inferior temporal sulcus Occipito temporal sulcus Occipito temporal gyrus lateral Para hippocampal gyrus Collateral sulcus Fusiform gyrus Collateral sulcus Occipito temporal sulcus Inferior temporal sulcus Sylvian fissure Inferior temporal sulcus Sup. temporal sulcus Sylvian fissure Sup. temporal sulcus Inferior temporal sulcus Occipito temporal sulcus Orientation of the main temporal sulci on 3D imaging 23

Temporal lobe: inferior Para hippocampalg yrus Collateral sulcus Fusiform gyrus Lingual gyrus Sup. temp. sulc. Sylvian fissure Inf. temp. sulc. CollateralChoroid fissure Para hippocampal gyrus Occip.temp. sulcusCollateral sulcus Insular cortex Temporal horn lateral ventricle Sup.temporal gyrus Middle temp. gyrus Fusiform Inf. temp. gyrus Para hippocampal gyrus Collateral sulcus Fusiform Temporal pole Orientation of the main temporal sulci on 3D imaging 24

Temporal lobe and Limbic lobe : Amygdaloid nucleus, Hippocampus Hippocampus Amygdala Temporal pole Amygdala HippocampusChoroid fissure Hippocampus Parahippocamp.gyrus Temporal horn lateral ventricle Fusiform Fornix Para hipp. gyrus Lingual Orientation of the main temporal sulci on 3D imaging 25

Temporal lobe, temporo occipital area, post. Ammon’s horn Atrium lateral ventricle Hippocampus projection of the most posterior part Lingual gyrusCollateral sulcus Hippocampus posterior Fornix posterior pilar Lingual gyrus Collateral sulcus Hippocampus Ammon’s horn Sylvian fissure Orientation of the main temporal sulci on 3D imaging 26

Some references Text books Anatomy H.M. Duvernoy. The human brain Surface, blood supply and three- dimensional sectional anatomy 2 nd ed. Springer Wien New York 1999 R.Niewenhuys, J. Voogd, Chr.van Huijzen The human central nervous system. Asynopsis Atlas 3 rd ed. Springer verlag Berlin Heidelberg, New York 1988 A new edition, the 4 th will be available in March 2007 A.Parent Carpenter’s Human Neuroanatomy 9 th ed. Williams and Wilkins Baltimore, Philadelphia, Hong Kong et al 1996 J.Talairach and J.P. Tournoux Coplanar Stereotaxic Atlas of the Human Brain. G. Thieme verlag Stuttgart, New York 1988 Web sites Interactive atlases. Digital anatomist project Salamon’s Neuroanatomy and Neurovasculature Web Atlas resource 27