25 Lateral (A) and medial (B) views of the cerebral hemisphereshowing the landmarks used to divide the cortex into its main lobes.
On the lateral aspect, the central sulcus (of Rolando) separatesfrontal and parietal lobes. The lateral sulcus (of Sylvius) forms the bor-der between frontal and temporal lobes. The occipital lobe is locatedcaudal to an arbitrary line drawn between the terminus of the parieto-occipital sulcus and the preoccipital notch. A horizontal line drawnfrom approximately the upper two-thirds of the lateral fissure to therostral edge of the occipital lobe represents the border between pari-etal and temporal lobes. The insular cortex (see also Figs. 2-46 on page45 and 3-1 on page 56) is located internal to the lateral sulcus. This part
of the cortex is made up of long and short gyri that are separated fromeach other by the central sulcus of the insula. The insula, as a whole, isseparated from the adjacent portions of the frontal, parietal, and tem-poral opercula by the circular sulcus.
On the medial aspect, the cingulate sulcus separates medial portionsof frontal and parietal lobes from the limbic lobe. An imaginary con-tinuation of the central sulcus intersects with the cingulate sulcus andforms the border between frontal and parietal lobes. The parieto-occipital sulcus and an arbitrary continuation of this line to the preoc-cipital notch separate the parietal, limbic, and temporal lobes from theoccipital lobe.
The Brain: Lobes 13
Central sulcus
Central sulcus
Precentral sulcus
Lateral sulcus
Paracentral sulcus
Cingulate sulcus
Corpus callosum
Marginal sulcus (marginalramus of the cingulatesulcus)
Parietooccipitalsulcus
Calcarinesulcus
Collateral sulcus
Fornix
Diencephalon
Postcentral sulcus
Parietooccipitalsulcus
Frontal
Lobes
Parietal
Temporal
Occipital
Limbic
Insular
Preoccipitalnotch
Preoccipital notch
B
A
14 External Morphology of the Central Nervous System
26 Lateral (A) and medial (B) views of the cerebral hemisphereshowing the more commonly described Brodmann areas. In general,area 4 comprises the primary somatomotor cortex, areas 3,1, and 2 theprimary somatosensory cortex, and area 17 the primary visual cortex.Area 41 is the primary auditory cortex, and the portion of area 6 in thecaudal part of the middle frontal gyrus is generally recognized as thefrontal eye field.
The inferior frontal gyrus has three portions: a pars opercularis, pars
triangularis, and a pars orbitalis. A lesion that is located primarily in ar-eas 44 and 45 (shaded) will give rise to what is called a Broca aphasia,also called expressive or nonfluent aphasia.
The inferior parietal lobule consists of supramarginal (area 40) andangular (area 39) gyri. Lesions in this general area of the cortex(shaded), and sometimes extending into area 22, will give rise to whatis known as Wernicke aphasia, also sometimes called receptive or flu-ent aphasia.
Precentral gyrus
Pars opercularis
Pars triangularis
Pars orbitalis
Posterior paracentral gyrus
Anterior paracentral gyrus
Cuneus
Calcarine sulcus
Lingual gyrus
Postcentral gyrus
Surpamarginal gyrus
Angular gyrus
5
41
42
5
18
19
47
3,1,2
4544
8
6 4
40
39
22
3,1,2
8 6 4
7
19
18
17
7
19
18
17
A
B
The Brain: Lobes 15
27 Lateral (A) and medial (B) views of the cerebral hemisphereshowing the somatotopic organization of the primary somatomotorand somatosensory cortices. The lower extremity and foot areas are lo-cated on medial aspects of the hemisphere in the anterior paracentral(motor) and the posterior paracentral (sensory) gyri. The remainingportions of the body extend from the margin of the hemisphere overthe convexity to the lateral sulcus in the precentral and postcentralgyri.
In general, the precentral gyrus can be divided into three regions:the lateral third representing the face area, the middle third represent-
ing the hand and upper extremity areas, and the medial third repre-senting the trunk and the hip. Lesions of the somatomotor cortex re-sult in motor deficits on the contralateral side of the body while lesionsin the somatosensory cortex result in a loss of sensory perception fromthe contralateral side of the body.
The medial surface of the right hemisphere (B) illustrates the posi-tion of the left portions of the visual field. The inferior visual quadrantis located in the primary visual cortex above the calcarine sulcus whilethe superior visual quadrant is found in the cortex below the calcarinesulcus.
Posrcentral gyrus (primary somatosensory cortex)Precentral gyrus (primary somatomotor cortex)
Posterior paracentral gyrus (somatosensory)Anterior paracentral gyrus (somatomotor)
Leftinferiorvisualquadrant
A
B
28 Dorsal view of the cerebral hemispheres showing the main gyriand sulci and an MRI (inverted inversion recovery—lower left) and aCT (lower right) identifying structures from the same perspective.
Note the area of infarction representing the territory of the anteriorcerebral artery (ACA).
16 External Morphology of the Central Nervous System
Longitudinal fissure
Superior frontalsulcus (SFSul)
Precentralsulcus (PrCSul)
Precentralgyrus (PrCGy)
Centralsulcus (CSul)
Postcentralgyrus (PoCGy)
Postcentral sulcus
Occipital gyri
Superior parietal lobule
Supramarginalgyrus
Centralsulcus (CSul)
Precentralgyrus (PrCGy)
Middle frontalgyrus (MFGy)
Superior frontalgyrus (SFGy)
Anteriorcerebralarteries
SFGy
CSul
PoCGy
MFGy
SFSul
PrCSul
PrCGy
Falxcerebri
ACAterritory
18 External Morphology of the Central Nervous System
211 Lateral view of the left cerebral hemisphere showing theprincipal gyri and sulci and an MRI (inversion recovery) identifyingmany of these structures from the same perspective.
CSul
PrCSul
MFGy
IFSul
POrb
PTr
PoP
LatSul
PrCGy
CSul
PoCSul
OGy
MTGy
STGy
STSul
PoCGy
Precentral sulcus (PrCSul)
Superior frontal gyrus
Superior frontal sulcus
Middle frontal gyrus (MFGy)
Inferior frontal sulcus (IFSul)
Inferior frontal gyrus:
Pars opercularis (PoP)
Pars triangularis (PTr)
Pars orbitalis (POrb)
Lateral sulcus (LatSul)
Superior temporal gyrus (STGy)
Superior temporal sulcus (STSul)
Middle temporal gyrus (MTGy) Preoccipital notch
Occipitalgyri (OGy)
Angular gyrus
Interparietal sulcus
Supramarginal gyrus
Superior parietal lobule
Postcentral sulcus (PoCSul)
Central sulcus (CSul)
Precentral gyrus (PrCGy)
Postcentral gyrus (PoCGy)
20 External Morphology of the Central Nervous System
214 Ventral view of the cerebral hemispheres and diencephalonwith the brainstem caudal to midbrain removed and two MRIs (inver-
sion recovery—lower left; T2-weighted—lower right) showing manystructures from the same perspective.
Middlecerebralartery
Hypothalamus
Anteriorcerebralartery
Cerebellum
Temporal lobe
Un
CC
OlfSul
OrbGy
GyRec
OpTr
MB
IPF
Col
OpTr
Un
IPF
CA
Col
Olfactory bulb
Gyrus rectus (GyRec)
Olfactory tract
Optic nerve
Optic chiasm
Optic tract (OpTr)
Interpeduncularfossa (IPF)
Inferior temporalgyrus
Crus cerebri (CC)
Substantia nigra
Cerebralaqueduct (CA)
Colliculi (Col)
Frontal pole
Olfactory sulcus (OlfSul)
Orbital gyri (OrbGy)
Temporal pole
Infundibulum
Uncus (Un)
Mammillarybody (MB)
Parahippocampalgyrus
Collateral sulcus
Occipitotemporalgyri
Lingual gyrus
Occipital gyri
Occipital pole
22 External Morphology of the Central Nervous System
217 Ventral view of the cerebral hemispheres, diencephalon,brainstem, and cerebellum and two MRIs (both T1-weighted images)that shows structures from the same perspective. A detailed view of theventral aspect of the brainstem is seen in Figure 2-20 on page 24.
Olfactory bulb
Orbital sulci
Gyrus rectus (GyRec)
Olfactory tract
Basilar pons (BP)
Occipitotemporalsulcus
Occipitotemporalgyri
Glossopharyngealnerve
Flocculus
Vagus nerve
Medulla
Decussationof pyramids
Frontal pole
Longitundinal fissure
Olfactory sulcus (OlfSul)
Orbital gyri (OrbGy)
Temporal pole (TPole)
Uncus
Parahippocampalgyrus
Collateralsulcus
Middle cerebellarpeduncle (MCP)
Facial nerve
Vestibulocochlearnerve
Abducens nerve
Olive (inferior); olivary eminence
Cerebellum (Cbl)
BP
GyRec OlfSul
OrbGy
Tpole
Trigeminalnerve
MCP
Fourthventricle
Cbl
BP
24 External Morphology of the Central Nervous System
220 Detailed ventral view of the diencephalon and brainstemwith particular emphasis on cranial nerves and related structures. Thedots on the left side represent the approximate position of the roots of
the hypoglossal nerve on that side; the general position of the (spinal)accessory nerve is shown on the right by the dark line.
Gyrus rectus
Infundibulum
Mammillary body
Interpeduncularfossa
Basilar pons
Trochlear nerve (cranial nerve IV)
Trigeminal nerve(cranial nerve V)
Middle cerebellar peduncle(brachium pontis)
Flocculus
Olive (inferior);olivary eminence
Retroolivary sulcus(postolivary sulcus)
Choroid plexus
Preolivary sulcus(exit of XIIth Nr.)
Pyramid
Anterior median fissure
Decussationof pyramids
Olfactory tract
Optic nerve(cranial nerve II)
Optic chiasm
Optic tract
Oculomotor nerve(cranial nerve III)
Crus cerebri
Parahippocampalgyrus
Abducens nerve(cranial nerve VI)
Facial nerve(cranial nerve VII)
Intermediate nerve
Vestibulocochlear nerve(cranial nerve VIII)
Glossopharyngeal nerve(cranial nerve IX)
Vagus nerve(cranial nerve X)
Hypoglossal nerve(cranial nerve XII)
Accessory nerve(cranial nerve XI)
Brs of posterior inferiorcerebellar artery
26 External Morphology of the Central Nervous System
223 View of the ventral aspect of the diencephalon and part of thebrainstem with the medial portions of the temporal lobe removed.
Note structures of the hypothalamus, cranial nerves, and optic struc-tures, including the lateral geniculate body.
Lateral geniculatebody
Crus cerebri
Trochlear nerve
Optic tract
Optic chiasm
Optic nerve
Infundibulum
Trigeminal nervemotor root
Trigeminal nervesensory root
Basilar pons
Abducens nerve
Pyramid
Preolivary sulcus
Middle cerebellarpeduncle
Vestibulocochlearnerve
Facial nerve
Olive (inferior),olivary eminence
Retroolivary sulcus(postolivary sulcus)
222 Lateral view of the left side of the brainstem emphasizingstructures and cranial nerves on the ventral aspect of the thalamus and
brainstem. Compare with Figure 2-24 on the facing page. The cere-bellum and portions of the temporal lobe have been removed.
Anterior cerebralartery
Optic nerve
Optic chiasm
Optic tract
Posterior perforated substance
Trochlear nerve
Lateral geniculate body
Medial geniculate body
Middle cerebellar peduncle
Vestibulocochlear nerve
Olfactory tract
Medial olfactory stria
Lateral olfactory stria
Anterior perforated substance
Infundibulum
Mammillary body
Crus cerebri
Basilar pons
Trigeminal nerve
Abducens nerve
Facial nerve
Pyramid
28 External Morphology of the Central Nervous System
226 Midsagittal view of the right cerebral hemisphere and dien-cephalon, with brainstem removed, showing the main gyri and sulciand two MRI (both T1-weighted images) showing these structuresfrom the same perspective. The lower MRI is from a patient with asmall colloid cyst in the interventricular foramen. When compared tothe upper MRI, note the enlarged lateral ventricle with resultant thin-ning of the corpus callosum.
A colloid cyst (colloid tumor) is a congenital growth usually dis-covered in adult life once the flow of CSF through the interventricularforamina is compromised (obstructive hydrocephalus). The patientmay have headache, unsteady gait, weakness of the lower extremities,visual or somatosensory disorders, and/or personality changes or con-fusion. Treatment is usually by surgical removal.
Rhinal sulcus
Anterior paracentral gyrus (APGy)
Precentral sulcus (PrCSul)
Paracentral sulcus (ParCSul)
Cingulate sulcus(CinSul)
Superior frontal gyrus (SFGy)
Cingulate gyrus (CinGy)
Sulcus of corpuscallosum (SulCC)
Paraterminal gyri
Parolfactory gyri (ParolfGy)
Temporal pole UncusParahippocampal gyrus
Occipitotemporal gyri
Isthmus of cingulate gyrus
Lingual gyrus(LinGy)
Calcarine sulcus(CalSul)
Cuneus (Cun)
Parietooccipitalsulcus (POSul)
Precuneus (PrCun)
Marginal sulcus (MarSul)
Posterior paracentral gyrus (PPGy)
Central sulcus (CSul)
PrCSul
ParCSul
SulCC
CinGy
CinSul
ParolfGy
APGy
CSul
PPGy
MarSul
PrCun
POSul
Cun
CalSul
LinGy
MarSul
POSul
CalSul
Internal cerebralvein
SFGy
Corpus callosum
Colloid cyst
30 External Morphology of the Central Nervous System
229 A midsagittal view of the right cerebral hemisphere and di-encephalon with the brainstem and cerebellum in situ. The MRI (T1-weighted image) shows many brain structures from the same perspec-tive.
Anterior paracentral gyrus (APGy)
Paracentral sulcus (PCSul)
Superior frontal gyrus (SFGy)
Body of corpus callosum (BCorC)
Sulcus of thecorpus callosum (SulCorC)
Cingulate gyrus (CinGy)
Cingulate sulcus (CinSul)
Septum
Rostrum of corpus callosum (RCorC)
Fornix (For)
Midbrain tegmentum (MidTeg)
Basilar pons (BP)
Pontine tegmentum (PonTeg)
Central sulcus (CSul)
Posterior paracentral gyrus (PPGy)
Marginal sulcus (MarSul)
Precuneus (PCun)
Splenium of corpus callosum (SplCorC)
Parietooccipitalsulcus (POSul)
Cuneus (Cun)
Lingual gyrus (LinGy)
Calcarine sulcus (CalSul)
Cerebellum (Cbl)
Tonsil of cerebellum (Ton)
Medulla (Med)
APGyPCSulSFGy
BCorC
SulCorC
CinGy
CinSul
GCorC
RCorC
For
MidTeg BP PonTeg
CSul
PPGy
MarSul
PCun
SplCorC
POSul
Cun
LinGy
CalSul
Cbl
TonMed
Genu of corpuscallosum (GCorC)
The Brain: Gross Views, Vasculature, and MRI 31
230 A midsagittal view of the right cerebral hemisphere and di-encephalon with the brainstem in situ focusing on the details primarilyrelated to the diencephalon and third ventricle. The MRI (T1-weighted
image) shows these brain structures from the same perspective. Hyth� hypothalamus.
Body of fornix (For)
Septum pellucidum (Sep)
Interventricular foramen
Column of fornix
Anteriorcommissure (AC)
Lamina terminalis
Infundibulum (In)
Supraoptic recess
Optic chiasm (OpCh)
Optic nerve
Infundibular recess
Mammillary body (MB)
Hypothalamic sulcus
Oculomotor nerve
Interpeduncular fossa (IpedFos)
Basilar pons (BP)
Massa intermedia
Dorsal thalamus (DorTh)
Choroid plexus of third ventricle
Stria medullaris thalami
Habenula
Suprapinealrecess
Posteriorcommissure
Pineal (P)
Superiorcolliculus (SC)
Quadrigeminalcistern (QCis)
Inferiorcolliculus (IC)
Cerebralaqueduct (CA)
Anterior medullary velum (AMV)
Fourth ventricle (ForVen)
Posterior inferior cerebellar artery
Medulla
DorTh
Internal cerebral vein
P
Tentorium cerebelli
QCis
IC
SC
AMV
ForVen
CABPIpedFos
For
Sep
AC
Hypothalamus
OpCh
In
Pituitary gland
MB
HythHyth
32 External Morphology of the Central Nervous System
231 Rostral (A, superior surface), caudal (B, inferior surface),and an inferior view (C, inferior aspect) of the cerebellum. The viewin C shows the aspect of the cerebellum that is continuous into thebrainstem via cerebellar peduncles. The view in C correlates with su-perior surface of the brainstem (and middle superior cerebellar pe-duncles) as shown in Figure 2-34 on page 34.
Note that the superior view of the cerebellum (A) correlates closely
with cerebellar structures seen in axial MRIs at comparable levels (D,E). Structures seen on the inferior surface of the cerebellum, such asthe tonsil (F), correlate closely with an axial MRI at a comparable level.In G, note the appearance of the margin of the cerebellum, the generalappearance and position of the lobes, and the obvious nature of themiddle cerebellar peduncle. All MRI images are T1-weighted.
Anteriorquadrangularlobule
Posteriorquadrangularlobule
Hemisphere
Hemisphere
Anteriorlobe (AntLb)
Horizontalfissure
Flocculus (Fl)
Tonsil (Ton)
Nodulus
Cerebellar peduncles:
Superior (SCP)Middle (MCP)Inferior Primary fissure
AntLb
MCP
Fl
Posteriorlobe (PostLb)
Basilar pons (Bpon)
Medulla (Med)Flocculus (Fl)
Tonsil (Ton)
Biventerlobule
Gracilelobule
Inferiorsemilunar
lobule
Bpon
AntLb
SCP
Fourth ventricle
Med
Med
Ton
PostLb
PostLb
Ver
Primaryfissure
Anteriorlobe (AntLb)
Midbrain
Posteriorsuperior
fissure
Superior semilunarlobule
Vermis (Ver)
Vermis (Ver)
Colliculi:
SuperiorInferior
A
B
C
D
E
F
G
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