Cerebrum Anatomy

 

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Rhoton Anatomy

Cerebrum

I.
Hemispheres

a.     Separated
by the longitudinal fissure (interhemispheric fissure)

b.     Connected
by the corpus callosum lateral and merge inferiorly with the diencephalons

c.     Encase
the lateral and third ventricle

d.     Three
surfaces


i.    
Lateral-
referred to as the convexity faces the cranial cap laterally


ii.    
Medial


iii.    
Basal

e.     Three
Margins


i.    
Superior


ii.    
Inferior


iii.    
Medial

f.      Three
Poles


i.    
Frontal


ii.    
Temporal


iii.    
Occipital

g.     Three
types of white matter fibers


i.    
Projection


ii.    
Commisural


iii.    
Association

h.     Five
Lobes


i.    
Frontal


ii.    
Parietal


iii.    
Temporal


iv.    
Occipital


v.    
Insular

i.      Most
important surgical landmarks


i.    
Borders,
poles, sylvian and interhemispheric fissure, and central sulcus

II.
Sylvian Fissure

a.     Carries
the MCA

b.     Provides
surgical access to the anterior part of the basal surface and cranial base

c.     Superficial
Sylvian Fissure


i.    
Stem-
begins medially at the anterior clinoid process à laterally along the
sphenoid ridge to the pterion where it divides into the rami


ii.    
Rami-
Anterior Horizontal, Anterior Ascending and Posterior Rami

1.     Posterior
ramus is just a contituation of the sylvian fissure

d.     Sylvian
cistern


i.    
Deep
to the sylvian fissure


ii.    
Divided
into 2 compartments:

1.     Sphenoidal

a.     Extends
laterally around the ICA

b.     Roof
is formed by the posterior orbital surface of the frontal lobe and the anterior
perforated substance

Superior to the roof is the
caudate and lentiform nucleus and the AL of the internal capsule

c.     Floor-
formed by anterior part of planum polare (part of the upper temporal lobe- a
shallow cupped trench here holds the MCA)


i.    
Medial
part of the floor- Anterior portion of the uncus, amygdala

d.     Lateral
edge- Limen insulae- prominence overlying the cingulum (connects the frontal
and temporal lobes)

2.     Operculoinsular

a.     Formed
by two narrow clefts: opercular and insular

b.     Opercular
cleft- between the sylvian surface of the frontal lobe and the parietal lobe


i.    
Upper
lip- formed by the gyri of the frontal and parietal lobes that continue
medially around the fissure to form the roof of the sylvian cistern (Mà
L: pars orbitalis, triangularis, opercularis; precentral, postcentral, and
supramarginal gyri)


ii.    
Lower
lip- (pàa)
planum temporale (which is made up of the transverse temporal gyri part of
which is Heschl’s gyrus) and part of the planum polare lateral to the insula

Heschl’s gyrus and the adjoining
part of the Superior temporal gyrus serves as the primary
auditory receiving area (Wernicke’s)

c.     Insular
cleft-


i.    
superior limb- located between the insula and opercula

d.     Upper
lip

e.     Sylvian
point- posterior portion of the MCA where the artery turns away from the insula
toward the atrium

f.      Safest
point to begin splitting the fissure


i.    
Start
at the natural upward reflection of the apex of the pars triangularis: located
directly lateral to the anterioinferior part of the circular sulcus and the
anterior limit of the basal ganglia

III.
Anterior Perforated Substance

a.     Flat,
smooth area of gray matter located in the roof of the sphenoidal compartment of
the sylvian fissure

b.     Has
small perforating arteries from the ICA, anterior choroidal, ACA, MCA that are
trying to reach the BG, thalamus, internal capsule

c.     Bounded


i.    
Anteriorly-
medial and lateral olfactory striae


ii.    
Posterolaterally
by the stem of the temporal lobe


iii.    
Laterally-
by the limen insulae


iv.    
Posteromedially-
by they optic tract


v.    
Medially-
it extends above the optic chiasm to the anterior edge of the interhemispheric
fissure

d.     Just
above the APS- Frontal horn, head of the caudate, Anterior lentiform nucleus,
AL internal capsule

e.     Think
of the APS as the floor to the anterior half of the BG

IV.
Insula

a.     Triangular
Shape- with the apex directed toward the limen insulae (raised area over the
uncinate fasciculus)

b.     Circular
sulcus- separates the insula from the frontal, parietal, and temporal opercula

c.     Central
sulcus of the insula- nearly parallel to the central sulcus on the convexity

d.     Think
of the insula as the outer covering of the IC, BG, and thalamus

e.     The
superior temporal sulcus- parallels the lower border of the insula

f.      The
optic tract- provides a deep landmark to the insula as it courses in the roof
of the ambient cistern near the midline

V.
Central Sulcus

a.     Separates
motor (anterior) and sensory (posterior)

VI.
Frontal Lobe

 

Joseph MillerCerebrum Anatomy

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