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Chapter 3 CNS Gross Anatomy
 Chris Rorden
University of South Carolina
Norman J. Arnold School of Public Health
Department of Communication Sciences and Disorders
University of South Carolina
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Key Objective
To be able to identify the level of the CNS by
recognizing the landmarks in transverse,
horizontal, and coronal sections
– Brain, brainstem, spinal cord
– Requires practice and drill
– Use book, atlases and software
– Look for shape, size, location and proximity to
other features.
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Easy to spot changes
Pyramidal Tract Changes
– Cortical + Subcortical
Ventricular Changes
– All levels – including fourth ventricle and brainstem
– Changes in shape of brainstem and spinal cord
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Crucial anatomy
Horizontal and Coronal Views
– Pyramidal Tracts
– Cerebellum
– Thalamus
– Internal Capsule
– Basal Ganglia
Putamen
Globus Pallidus
Caudate Nucleus
–Hippocampus
–Fornix
–Ventricles
–Corpus Callosum
–Optic tract
–Insula
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Pyramidal tract
Corona Radiata
Aka ‘Corticospinal tract’.
Massive bundle of axons that
contect cortex to spinal cord.
Mostly voluntary motor
control.

http://library.med.utah.edu/kw/hyperbrain/syllabus/syllabus10.html
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Primary Motor Cortex
M1 is principle origin for pyramidal tract.
– Spatial organization (homunculus)
M1: movement
S1: sensation
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Pyramidal Cells
Neurons in layers V and VI
send axons long distances.
Layer V of M1 the pyramidal
cells are extremely large. (Betz
cells).
Dendrites go into superficial
layers.
Axon travels down pyramidal
tract.
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Corona Radiata
Near the motor
cortex, we refer to
the fibers of the
pyramidal tract as
being in the
‘corona radiata’.
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Internal Capsule
Near the basal ganglia, the
pyramidal tract forms the central
body (genu) of the internal
capsule.
Internal capsule and
neighboring basal
ganglia often injured by
small strokes.
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Peduncles
Pes Pedunculi
(part of Cerebral peduncle)
A
P
P
A
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Motor Fibers in the Pons
A
Corticospinal Tract
A
P
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Motor Fibers in the Medulla
A
Pyramidal Tract
P
A
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Motor Fibers in the Spinal Cord
P
Lateral
Corticospinal
Tract
Pyramidal Tract
A
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CSF
Cerebral Aqueduct
Lateral Ventricles
Fourth Ventricle
Third Ventricle
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Ventricles
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Sections of the Brain
Note whether views are
– Axial (Horizontal) Views
– Coronal Views
– Less need for familiarity with sagittal view
Look for relationships and shapes of structures
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Cerebellum
Heavily folded
appearance – huge
number of neurons.
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Thalamus
Difficult to see on MRI
scan – similar contrast to
nearby white matter
Major portion of
diencephalon
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Thalamus
 Sensory information is relayed
to the cortex via the thalamus.
 Auditory, somatic, visceral,
gustatory and vision (but not
smell) each have dedicated
nuclei in thalamus.
 Not just relaying information:
thalamic nuclei have
reciprocal connections with
cortex. Regulates level of
awareness - damaged can
lead to coma.
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Thalamus: medial, posterior to basal ganglia
Head of
Caudate
Nucleus
Cleft for
Internal Capsule
Thalmus
Putamen
Amygdaloid
Nucleus
Tail of
Caudate Nucleus
Lateral View
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Thalamus
Not seen on the more anterior coronal slices.
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Basal Ganglia
 Basal Ganglia (CN+Putamen referred to as striatum)
–
–
–
–
Caudate nucleus near lateral ventricle
Putamen (yellow): superficial
Globus pallidus (green): deep
Nucleus accumbens: (not shown – junction of CN and Putamen)
Function: initiating
action. Involved with
parkinson disease.
Also involved with
motivation,
addiction.
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Basal Ganglia
Coronal slices
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Papez Circuit
Hippocampus, fornix and
mammillary body crucial for
long term memory.
A difficult structure to visualize.
A
P
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Hippocampus
Hippocampus: coronal view reveals folded shape.
Fornix also visible in this view.
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Corpus Callosum
Massive white matter bundle that connects the
two hemispheres
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Corpus Callosum
Sometimes surgically severed to treat epilepsy
– ‘Split brain patients’
– Connections mostly homotopic
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The optic tract
 Lesions at different locations lead
to different forms of visual field
cuts.
 Important diagnostic tool to infer
brain injury.
Lateral
Geniculate Nucleus
(Thalamus)
V1 Primary Visual Cortex
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Visual Defects
 Field defects reveal
anatomical injury
A. Monocular blindness
B. Monocular
quadrantanopia
C. Bitemporal hemianopia
D. Homonymous hemianopia
E. Upper quadrantanopia
F. Lower quadrantanopia
G. Homonymous hemianopia
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V1
Primary visual
cortex (V1) lies in
calcarine fissure.
Complete damage
leads to
Homonymous
hemianopia.
Partial damage
leads to scotomas
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V1 – retinotopic mapping
V1 is retinotopic:
distorted spatial map of
visual scene
Fovea has massively
over represented.
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Insular Cortex
Insula: below the portions
of the frontal, temporal,
and parietal lobes
Insular Cortex
 Sometimes referred to as Insular Lobe
 Operculum (lids) separate the insula and the
superficial cortex.
 Temporal Operculum
(inferior bank)
 Parietal Operculum
(posterior+superior)
 Frontal Operculum
(anterior+superior)