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Chapter 3 CNS Gross Anatomy

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. Key Objective.

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Chapter 3 CNS Gross Anatomy

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  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 University of South Carolina

  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. 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. 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. 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

  6. 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 Pons A Corticospinal Tract A P

  12. Motor Fibers in the Medulla A Pyramidal Tract P A

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

  14. CSF Lateral Ventricles Cerebral Aqueduct Third Ventricle Fourth Ventricle

  15. Ventricles

  16. 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. 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 • Homonymous hemianopia

  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

  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)

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