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Chapter 3 CNS Gross Anatomy

Chris RordenUniversity of South CarolinaNorman J. Arnold School of Public HealthDepartment of Communication Sciences and DisordersUniversity 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

PutamenGlobus PallidusCaudate Nucleus

–Hippocampus

–Fornix

–Ventricles

–Corpus Callosum

–Optic tract

–Insula

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Pyramidal tract

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

Corona Radiata

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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

A

P

Pes Pedunculi (part of Cerebral peduncle)

AP

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Motor Fibers in the Pons

Corticospinal Tract

A

A

P

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Motor Fibers in the Medulla

Pyramidal Tract

A

A

P

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Motor Fibers in the Spinal Cord

Pyramidal TractLateral

CorticospinalTract

A

P

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CSF

Lateral Ventricles

Third Ventricle

Cerebral Aqueduct

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 forInternal Capsule

Head ofCaudateNucleus

Thalmus

Putamen

AmygdaloidNucleus

Tail ofCaudate 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.

PA

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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.

LateralGeniculate 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.

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)