Chapter 3 CNS Gross Anatomy

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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 (Cerebral peduncle)
A
A
P
P
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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
Lateral Ventricles
Cerebral Aqueduct
Third Ventricle
Fourth 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
Cleft for Internal Capsule
Head of Caudate Nucleus
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 (historically referred to as part
  of 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
A

• Hippocampus, fornix and mammillary body crucial
  for long term memory.
• A difficult structure to visualize.

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 optice 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
• Monocular blindness
• Bitemporal hemianopia
• Homonymous hemianopia
• Upper quadrantanopia
• Lower quadrantanopia
• 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

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Insular Cortex

• Sometimes referred to as Insular Lobe
• Operculum (lids) separate the insula and the
  superficial cortex.
• Temporal Operculum(inferior bank)
• Parietal Operculum(posteriorsuperior)
• Frontal Operculum(anteriorsuperior)