Ascending And Descending Tracts Of Spinal Cord Ppt Page
Slide deck: Ascending and Descending Tracts of the Spinal Cord (PowerPoint-ready)
Slide 7: TRACT 1 – Dorsal Column-Medial Lemniscus (DCML)
- Modalities: Fine (discriminative) touch, vibration, conscious proprioception (joint position sense).
- Pathway (Three Neurons):
- 1st order: DRG → ascends ipsilaterally in posterior funiculus → Nucleus gracilis (lower body) or cuneatus (upper body) in medulla.
- 2nd order: Decussates in medulla (internal arcuate fibers) → forms medial lemniscus → VPL of thalamus.
- 3rd order: VPL → primary somatosensory cortex (postcentral gyrus).
- Key PPT Feature: Animate the decussation at the medulla.
- Clinical Pearl: Loss of vibration and joint position sense ipsilateral to a cord lesion below the lesion (e.g., tabes dorsalis in syphilis).
ASCENDING TRACTS (Sensory)
Slide 6: Spinocerebellar Tracts (Posterior & Anterior)
- Sensory modalities: Unconscious proprioception (muscle & joint position for coordination).
- Posterior (dorsal): Ipsilateral; does not decussate.
- Anterior (ventral): Decussates twice (effectively ipsilateral).
- Destination: Cerebellum (no conscious perception).
- Clinical: Not affected by spinal cord hemisection because input reaches cerebellum via multiple routes.
Diagrams & visuals (what to include)
- Large spinal cord cross-section with colored overlays for each tract (label dorsal/ventral/lateral funiculi)
- Simplified pathway arrows from cortex/periphery to spinal cord and brainstem showing decussation points
- Small clinical schematic for Brown-Séquard and anterior cord syndrome
- Icons for modalities (touch, pain, proprioception, motor) for quick visual reference
Slide 6: Spotlight – Lateral Spinothalamic Tract
- Pathway: Dorsal root ganglion → Lamina I, II (substantia gelatinosa) → decussate via anterior commissure → ascend contralateral lateral funiculus → VPL of thalamus → cortex.
- Clinical pearl: Brown-Séquard syndrome (hemisection) → contralateral loss of pain/temp 1-2 segments below lesion.
Visual: Step-by-step arrow diagram.
Part 4: Clinical Syndromes & The "PPT-Ready" Wrapping (Slides 20-24)
Slide 17: Somatotopic Organization – The "Homunculus" in the Cord
- In the Lateral Corticospinal Tract:
- Cervical fibers (arms) → Medial.
- Lumbosacral fibers (legs) → Lateral.
- Clinical Relevance: A small central cord lesion (e.g., syringomyelia) affects the sacral fibers first? No – actually affects cervical fibers crossing for pain/temp. But for motor: lateral lesions affect legs, medial lesions affect arms.