This document provides an overview of brain anatomy as seen on MRI. It describes key structures including sulci, gyri and other anatomical landmarks of the different lobes and regions of the brain. Key points covered include the location and functions of the precentral and postcentral gyri, central sulcus, sylvian fissure and other cortical structures. Subcortical structures like the hippocampus, amygdala and hypothalamus are also described. The document outlines anatomy from the cerebral cortex down through the brainstem.

1. MR Brain Anatomy 2.0
Presented by Dr. Anil jangir
Guided by Dr. kirti rana chaturvedi

2. -Cortex is thicker over surface and sides of gyri, and
thinnest in the depths of the sulci.
- Cortex varies from 2-5 mm in thickness.
*It is conventional in
neuroradiology to
describe lesions as lying in
the subcortical (U-fibres
immediately below the
cortex), deep (white matter
core) or periventricular (thin
band of white matter
adjacent to the ependyma)
white matter

3. The central sulcus is separating
the precentral gyrus (motor)
from
the postcentral gyrus (sensory).
-The superior frontal sulcus is
identified between the superior
and middle frontal gyri. It
typically meets the precentral
sulcus almost at a right angle.
-Posterior to this lies the central
sulcus. The bulge in the
precentral gyrus represents the
hand motor area.
• Hand knob sign – Dorsally convex bulge of precentral gyrus
• Inverted omega sign- central sulcus
T sign

5. -Sagi<al T1 image- Parallel to the corpus callosum, the cingulate sulcus
(arrowheads) as it approaches the splenium turns towards the brain surface.
This extension, the pars marginalis of the cingulate sulcus, lies immediately
posterior to the central sulcus.
Bracket sign- Bihemispheric symmetrical part of pars marginalis od cingulate
sulcus shows anteriorly open bracket.
cingulate sulcus

6. Central sulcus
Sylvian fissure
f
T
p
Central sulcus separates frontal, parietal lobes.
Sylvian fissure separates frontal, parietal lobes above from temporal lobe
below.

7. - Precentral gyrus contains primary motor
cortex.
-Postcentral gyrus contains Primary
somatosensory cortex
-Premotor cortex: Within gyrus just anterior to
precentral gyrus.
-Superior & inferior parietal lobules lie posterior
to postcentral gyrus.

8. Corona radiata
Central sulcus
Precentral G
Corona radiata (centrum semiovale) is formed by fibers from all corHcal areas in internal
capsule fanning out into superior hemispheres.
Interhemispheric
fissure

9. • On axial T2 image, the intraparietal sulcus separates
the superior parietal lobule(medially) from the
inferior parietal lobule(laterally). Anteriorly, it
merges with the post central sulcus.
-The superior parietal lobule is
involved with the behavioral
interaction of an individual with
the surrounding space, and the
inferior parietal lobule with the
integration of diverse sensory
information for speech and
perception

10. H-shaped orbital sulci
• H-shaped orbital
sulci separaHng the
anterior (A),
posterior (P), medial
(M) and lateral (L)
orbital gyri. Gyrus
rectus (G) is
separated from the
medial orbital gyrus
by the olfactory
sulcus.
frontobasal sulci

11. b
infarct M sign of Inferior frontal gyrus

12. The anterior ascending and horizontal limbs of the Sylvian fissure
divide the M-shaped inferior frontal gyrus, below the inferior
frontal sulcus, into three parts pars opercularis, triangularis and
orbitalis. Broca’s area (motor speech) classically occupies the pars
opercularis.
-Wernicke’s area (recepHve speech) is usually centred on the
supramarginal gyrus.
-The inverted horseshoe-shaped supramarginal and angular gyri
are well shown in image(C).
-Medial parasagiTal image (D) show the triangular-shaped insular
cortex. Consistent bulge of Heschl’s gyrus (primary auditory
cortex) arising from the superior surface of the temporal lobe

14. CC
Calcarine
Sulcus
Y shaped parieto-occipital sulcus
-Occipital lobe is divided by calcarine sulcus into
lingual and cuneus gyrus

15. Occipito-parietal sulcus on axial image
-Deepest sulci posteriorly perpendicular to interhemispheric fissure

18. -Supramarginal gyrus lies at end of sylvian fissure
-Angular gyrus lies ventral to supramarginal gyrus
-Medial surface of parietal lobe is precuneus which lie immediately
rostral to parieto-occipital sulcus

21. Cingulate gyrus
body of caudate nucleus

22. ----Hippocampal tail is seen wrapping around midbrain & thalamus.
--External capsule lies between putamen & claustrum.
-Extreme capsule lies between claustrum & insula.
-

23. -Olfactory bulb/tract lies in/below olfactory sulcus
-Olfactory sulcus defines lateral margin of gyrus rectus.
-Collateral sulcus divides the lingual and parahippocampal gyrus from
medial occipitotemporal ( fusiform) gyrus.

24. -The middle frontal gyrus contains Brodmann’s area 8, known as the frontal eye field,
which is important for conjugate eye movements.

26. Wernickes area
temporal gyri of Heschl,
PercepHon of visual and
color

27. Tentorium cerebelli is a dural fold in horizontal plane separaHng
supratentorial & infratentorialcompartments & is conHnuous
superiorly with falx cerebri.

28. • T1 axial image shows the thin grey maTer layer
of the claustrum between the lenHform nucleus
and the insula cortex, separaHng the white
maTer of the external capsule medially from the
extreme capsule laterally.

29. LocaHon of lesion?

30. ---Lesion in front of parieto-occipital sulcus so answer is
posterior parietal lobe.
Next quesHon ?

31. --Answer is Cuneus gyri of Occipital lobe.
Next QuesHon?

32. Lesion is above the sylvian fissure and in front of central
sulcus So answer is posterior frontal lobe.
Next QuesHon

33. Association fibres
links cortical areas in
different lobes of same
hemisphere.
-Superior longitudinal
fasciculus running
in the white matter of the
parietal lobe linking
parietooccipital
and frontal lobes,
- Cingulum

34. -The anterior commissure (long arrow) and posterior
commissure (short arrow) forming the posterior border of the
cerebral aqueduct.
-Fornix and the massa intermedia or thalamic adhesion, within
the third ventricle.
* Third ventricle
bordered laterally by
the bulky grey matter
of the thalami that
frequently make
contact with each other
centrally as the massa
intermedia.

35. -Uncus forms medial border of temporal lobe, merges posteriorly with parahippocampal
gyrus.

36. • The uncal recess of the temporal horn of the lateral
ventricle turns medially, separaHng the amygdala (A)
from the hippocampal head (H).

38. (A) Amygdala (large arrow), uncus (short arrow), free margin of
tentorium cerebelli (thin arrow).
Coronal T2 MR images(a,b,c) from anterior to posterior,
demonstraHng the main limbic structures of the mesial
temporal lobe

39. (B) Hippocampal head (large arrow), uncal recess of temporal horn separaHng
posterior aspect of amygdala superiorly from hippocampal head inferiorly.
*Hippocampal head is recognized by digitaHons on its superior surface.

40. (C) Body of hippocampus (large arrow), parahippocampal gyrus (long
arrow), collateral sulcus (short arrow).
*Collateral sulcus separates parahippocampal gyrus from
occipitotemporal (fusiform) gyrus.
Red N

41. -Image at posterior thalamus (pulvinar) shows hippocampal
tail, smallest porHon of hippocampus.
-Fimbria arise from hippocampus & become crus of fornix
which aTaches to splenium.

42. Limbic system
- These include the amygdala, hippocampus,
parahippocampal gyrus, cingulate gyrus, subcallosal gyriand
associated structures
-The amygdala is the most anterior structure, separated
from the hippocampal head by the uncal recess of the
temporal horn.
- Limbic structures are associated with memory processing,
emoHonal responses, fight-or-flight responses, aggression
and sexual response: in summary, with acHviHes
contribuHng to preservaHon of the individual and the
conHnuaHon of the species

43. SagiTal T1 image. Hypothalamic border
(hypothalamic sulcus)

44. SagiTal T2 image demonstrates the structures in the floor of the third
ventricle: OpHc chiasm (1), pituitary infundibulum (2), tuber cinereum
(3) and mamillary bodies (4).

45. -The hypothalamus forms the floor of the third ventricle
and its side walls anteriorly following an oblique line
inferiorly from the foramen of Monro to the midbrain
Aqueduct.
- It consists of a group of nuclei serving a number
of autonomic, appeHte-related and regulatory funcHons
for the body as well as controlling and producing hormonal
output from the pituitary gland.
-The hypothalamus is inHmately linked to other limbic
structures and might be considered the output for the
limbic system.

47. • Midbrain
• Ventral: Cerebral peduncles (crus cerebri) containing
corticospinal, corticobulbar and corticopontine tracts
• Dorsal tegmentum: Ventral to cerebral aqueduct
Gray matter: Substantia nigra and red nucleus
Upper midbrain: Contains CN3 nucleus, at superior
colliculus level
Lower midbrain: Contains CN4 nucleus, at inferior
colliculus level
Tectum (quadrigeminal plate): Dorsal to cerebral aqueduct
• Superior & inferior colliculi
• Periaqueductal gray matter

48. cp
SN
RN

50. fourth cranial nerve, the only cranial nerve, exits from the dorsal aspect of the
brain stem

53. *CN3 susceptible to compression by PCA
aneurysms and uncal herniation

54. Image at level of lower pons shows facial nerve CN 7 &
vesHbulocochlear nerve CN8 coursing towards interior auditory canal.
- Nodulus of vermis may protrude into fourth ventricle & cause a
pseudolesion.

55. *Facial nerve is anterosuperior while the cochlear nerve is
anteroinferior

56. mid pons
Upper pons

57. Trigeminal nerve CNS is seen as it courses toward Meckel cave.
Dentate nucleus is only cerebellar nucleus that is seen on imaging

58. The pons comprises a bulbous convexity anteriorly, the basis pontis,
The posterior part of the pons, the pontine tegmentum, forms the floor
of the upper part of the fourth ventricle, and contains cranial
nerve nuclei (V, VI, VII, VIII).

59. C6!
*Arises in the prepontine
cistern

60. Medulla oblongata. On each side three bulges are visible in the contour of the
medulla: the pyramids (short arrow), olives (long arrow) and the inferior
cerebellar peduncle (broad arrow)

61. The medulla is the most caudal portion of the brain stem and continuous
with the cervical cord at the level of the foramen magnum.
Anteriorly, the pyramid has a protrusive appearance formed largely by
the corticospinal tracts.
Posterior and lateral to the pyramid is a very shallow groove called the
ventrolateral sulcus, in which the vertebral arteries usually lie.
Lateral to the pyramid is the olive corresponding to the inferior olivary
nucleus. Ventrolaterally, the ninth, tenth, and eleventh cranial nerves
emerge from the postolivary sulcus, and the twelfth cranial nerve
emerges from the preolivary sulcus.
Laterally, the inferior cerebellar peduncles, connecting the spinal cord
and medulla with the cerebellum.

62. -CN12 exits anterolateral medulla in preolivary sulcus while CN9,
CN10, & cranial roots of accessory CN 11 nerves exit lateral medulla in
postolivary sulcus.
mid medulla

63. T1 axial MRI
1- flocculus, 2- ventral median fissure, 3- medulla, 4- inferior
cerebellar peduncle 6- vermis

66. -SagiTal image of cerebellum.
Lobules of vermis are
demonstrated: lingula (1),
central lobule (2), culmen (3),
declive (4), folium (5), tuber (6),
pyramid (7), uvule (8) and
nodule (9).
-The roof of the fourth ventricle
is formed by the superior
medullary velum (SMV).
• 1. Primary fissure separates
culmen from declive.
• 2. Horizontal fissure
separates folium above from
tuber below.
• 3. Prepyramidal fissure
separates tuber from
pyramid.
1
2
3

68. -Primary (tentorial) fissure separates anterior culmen from posterior
declive.
-Horizontal (petrosal) fissure separates folium above from tuber below.
-Prebiventral/prepyramidal (suboccipital) fissure separates posterior
tuber from anterior pyramid.

69. (A)SagiTal T2 MR image. The tented apex of the fourth ventricle,
the fasHgium (large arrow) and the foramen of Magendie (small arrow) are well
shown.
(B) The rhomboid shape of the fourth ventricle is seen in coronal images. The
lateral recesses (arrows) funnel into the foramina of Luschka.
(C) Axial MR image through the caudal fourth ventricle demonstrate the foramen
of Magendie (large arrow) and foramina of Luschka (small arrows).
p
m
f
fm
L
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70. *In young females, the gland may fill the fossa with a convex upper
border.
-Posterior lobe often returning a high signal on T1-weighted
images due to neurosecretory granules in the neurohypophysis.