1. Chapter 3 CNS Gross Anatomy
Chris Rorden
University of South Carolina
Norman J. Arnold School of Public Health
Department of Communication Sciences and Disorders

2. 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.

3. Pyramidal Tract Changes Ventricular Changes
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

4. Horizontal and Coronal Views
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

5. Aka ‘Corticospinal tract’.
Pyramidal tract
Corona Radiata
Aka ‘Corticospinal tract’.
Massive bundle of axons that contect cortex to spinal cord.
Mostly voluntary motor control.

6. M1 is principle origin for pyramidal tract.
Primary Motor Cortex
M1 is principle origin for pyramidal tract.
Spatial organization (homunculus)
M1: movement
S1: sensation

7. 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.

8. Corona Radiata
Near the motor cortex, we refer to the fibers of the pyramidal tract as being in the ‘corona radiata’.

9. 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.

10. Peduncles
Pes Pedunculi
(part of Cerebral peduncle) A P A P

11. Motor Fibers in the PonsA
Corticospinal Tract A P

12. Motor Fibers in the Medulla
Pyramidal Tract P A

13. Motor Fibers in the Spinal Cord
Lateral
Corticospinal
Tract
Pyramidal Tract A

14. CSF Lateral Ventricles Third Ventricle Fourth Ventricle
Cerebral Aqueduct
Lateral Ventricles
Third Ventricle
Fourth Ventricle

15. Ventricles

16. Look for relationships and shapes of structures
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

17. Cerebellum
Heavily folded appearance – huge number of neurons.

18. Thalamus
Difficult to see on MRI scan – similar contrast to nearby white matter
Major portion of diencephalon

19. 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.

20. Thalamus: medial, posterior to basal ganglia
Cleft for
Internal Capsule
Head of
Caudate
Nucleus
Thalmus
Putamen
Amygdaloid
Nucleus
Tail of
Caudate Nucleus
Lateral View

21. Thalamus
Not seen on the more anterior coronal slices.

22. 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.

23. Basal Ganglia
Coronal slices

24. Papez Circuit A
Hippocampus, fornix and mammillary body crucial for long term memory.
A difficult structure to visualize. P

25. Hippocampus
Hippocampus: coronal view reveals folded shape.
Fornix also visible in this view.

26. Corpus Callosum
Massive white matter bundle that connects the two hemispheres

27. Sometimes surgically severed to treat epilepsy
Corpus Callosum
Sometimes surgically severed to treat epilepsy
‘Split brain patients’
Connections mostly homotopic

28. 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

29. Visual Defects Field defects reveal anatomical injury
Monocular blindness
Monocular quadrantanopia
Bitemporal hemianopia
Homonymous hemianopia
Upper quadrantanopia
Lower quadrantanopia

30. V1
Primary visual cortex (V1) lies in calcarine fissure.
Complete damage leads to Homonymous hemianopia.
Partial damage leads to scotomas

31. V1 – retinotopic mapping
V1 is retinotopic: distorted spatial map of visual scene
Fovea has massively over represented.

32. Insular Cortex
Insula: below the portions of the frontal, temporal, and parietal lobes
Insula: damage to this area has been linked to verbal dyspraxia
Dyspraxia: a dysfunction of motor planning in the absence of muscular weakness or muscular dysfunction
In the insula, it would be damage producing the simplest verbal gestures
Parahippocampus: emotional memory center

33. 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)