Injury and Potential for Recovery in the CNS

Question 1

What does brain injury lead to?

What is the damage pattern of a hypoxic brain injury?

What are the neuronal stages of MS?

What are the plaques seen in white matter tracts on an MRI?

How does an infection affect the brain? Symptoms?

Answer 1

• Inflammation and oedema; ↑ICP and Midline Shift
• Affects the most metabolically active parts more (Grey matter of cortex, Basal Ganglia)
• Autoimmune process of Inflammation → Demyelination → Neuronal Dysfunction
• Plaques of demyelination
• Headache, nausea and vomiting, lower consciousness, myoclonic
  jerks, fever (pyrexia)

Question 2

What is Axotomy?

What does an axotomy cause?

What is Retrograde degeneration?

What is Anterograde degeneration?

Answer 2

• Severed axon
• Loss of trophic factors and support from target axon
  o Target axon loses its normal input (Denervation); change in synaptic balance
• Damage towards cell body from where the axon is cut
• Damage away from cell body from where the axon is cut

Question 3

When can a severed axon in the PNS regrow?

Why is myelin important for axon regrowth?

Why can’t most CNS fibres regenerate?

What occurs during Gliosis (Glial scarring)?

How can gliosis be beneficial and detrimental?

What is the difference between Regeneration and Neurogenesis?

Answer 3

• If their myelin sheath remains intact
• Myelin provides guide tube for growing axon to reach its target neuron
• Environment isn’t optimal, Oligodendrocytes inhibit regeneration
• Reactive proliferation of Astrocytes and Microglia after injury; protective mechanism
• o Beneficial; Regenerates BBB and promotes Revascularisation of infarcted brain
  o Detrimental; Astrocytes secrete neurodevelopmental inhibitors, which prevents regrowth
• o Regeneration; Regrowth of severed axons, Occurs in PNS only
  o Neurogenesis; Birth of new neurons, Adult brain produces few neurons

Question 4

What is Neurorehabilitation?

What is Neural Plasticity? What are the 2 levels that it occurs on, and what are they due to?

What are the mechanisms by which neurorehabilitation takes place?

What is an example of neurorehabilitation in young children?

What is an example of neurorehabilitation in blind people?

Answer 4

• Restore and maximise function that was lost by remodelling of neural circuitry
• Structural and functional rearrangement of neural processes
  o Occurs on a Cellular level (due to learning) and Large-scale level (after injury)
• • Compensation; brain area taking over function of damaged area
  • Increased synaptic strength; form more synapses with target
  • Reorganisation; can lead to cortical remapping
• Hemispherectomy; language reorganisation and relative intellectual preservation
• Parts of visual cortex may be used for non-visual functions like reading Braille