L18 Spinal Cord Injury Flashcards
What happens to your function when you have a spinal cord injury?
Everything AT and BELOW the injury is lost or impaired, therefore injuries higher up on the spinal cord are more dangerous (in cervical or thoracic)
Injuries in the cervical area control breathing, H, head/neck movement
Injuries in the thoracic region control sympathetic tone (temp regulation and truck stability)
Where do the motor and sensory inputs come into the spinal cord?
Sensory inputs via dorsal roots
Motor inputs via ventral roots
Dorsal root ganglia contain cell bodies of sensory afferents
What is contained within the ascending nerve fibre tracts in the spinal cord?
Ascending: dorsal columns (touch/ proprioception/ vibration), spinocerebellar (movement regulation), spinothalamic (temp and pain, crosses immediately)
Descending: corticospinal (voluntary movement), reticulospinal/ vestibulospinal (walking and posture)
What is Brown-Sequard syndrome?
Lateral hemisection (spinal injury on one side), results in loss of temperature and pain sensation and motor function on opposite sides.
Impairs pain and temperature sensation on the opposite side of injury (because it crosses so early in the spinal cord)
Impairs proprioception and movement on the same side (because it crosses late in thr spinal cord)
Which age group is most commonly associated with spinal cord injuries?
16-30 years (43%) and then 31-41 (28%)
Usually due to accidents
Where does walking fall on the list of needs of SCI patients?
Relatively low, want independent respiration, repaired bowel and bladder and secual function first, as well as free of pain and spasms
What are the most common spinal cord injuries? What is relatively uncommon?
Bruising, stretching and compression of the spinal cord are most common injuries, with severed being pretty rare
What is the scale used to assess spinal cord injury?
American Spinal Injury Association (ASIA) Impairment Scale, assigns a letter from A (complete loss of function) to E (normal function) to determine the severity
What are the two groups that SCI patients are normally divided into?
Paraplegic: impairment of legs and lower trunk, impairment of bowel/ bladder and sexual function (midthoracic injury)
Quadriplegic (tetraplegic): partial or total loss of function in limbs and torso, impairment of bowel/ bladder/sec fxn, may be unable to breath if damage is in neck region (higher injury, cervical or high thoracic lesion)
What are the three main additional complication of SCI?
- Development of hyperactive reflexes and spasms
- Autonomic dysreflexia
- Loss of bladder and bowel control
How is baclofen used for SCI?
Intrathecal (administered via spinal canal) baclofen is used for reducing severe spasticity
It is a GABA B receptor agonist, therefore it increases presynaptic inhibition of transmission from sensory afferents (prevents reflexes)
Can also be given orally for mild spasticity
What is autonomic dysreflexia?
Loss of top down control of autonomic reflexes.
Extended bladder activates sympathetic division of the autonomic nervous system which results in dangerously high BP that is not compensated by central inhibition to the heart
How does a SCI impair bladder and bowel function?
Coordination of autonomic and somatic responses for normal bladder function require neural networks in the brain stem. Injury cuts of sympathetic and parasympathetic inputs to the brain stem resulting in no input from stretch receptors and no control of bladder muscles
What are 4 immediate treatments for SCI?
- Immobilization
- Sometimes spinal surgery to decompress cord, remove bone fragments, align vertebra
- Drugs to reduce swelling and inflammation
- Rehabilitation
What is secondary damage in SCI?
Increase in cell death and demyelination (loss of oligodendrocytes), in days/weeks following primary injury (impulses slower)
Factors involved:
Ischemia (reduced oxygenation of tissue)
Edema (swelling)
Glutamate increase (excitotoxicity)
Blood brain barrier breakdown
Inflammation (invasion of macrophages, and activation of microglia
What are two things that may be utilized to fix some aspect of SCI?
- Electrical stimulation of spinal cord in SCI patients evokes rhythmic activity in legs
- Treadmill therapy may improve walking (LOCOMAT)
What are the two main goals for future SCI research and intiatives?
To repair spinal cord damage
To enhance plasticity of undamaged neurons
What are the two reasons why damaged axons in the DNA do not regenerate?
Growth inhibitors on CNS myelin: CNS is hostile to new growth because it is so finely controlled and we do not want aberrant growth (possibility of cancer)
Mechanical barriers: axons run into barriers from scar tissue that prevents expansion
What are two SCI treatment strategies that are currently under investigation?
1, Promoting regeneration of damaged axons (blocking inhibitory growth molecules, bridging damaged regions, digesting scar tissue)
2. Enhancing the function of existing nerve cells (remyelinate axons, and promote sprouting)
What are growth inhibitory molecules?
Molecules on CNS myelin or extracellular matrix that prevent growth cone extension
Examples: Nogo-A, MAG, OMgp, CSPGs
How are antibodies used in SCI treatment?
Block inhibitors on myelin or their receptors on the growth cones, anti-Nogo therapy
What is involved in bridging the SC lesion as a form of treatment?
Mechanical bridges (inorganic and organic material), Schwann cells, olfactory ensheathing cells (glia from olfactory bulb), stem cell to produce growth promoting environment
What is involved in digesting the “glial scar”?
CSPG: chondroitin sulfate proteoglycan, part of ECM, upregulated by astrocytes after injury, therefore apply the enzyme chondroitinase to break it down
What is involved in remyelinating axons that were demyelinated after injury?
Use for stem cells engineered to produce oligodendrocytes, but the clinical trial was stopped because it was too costly and little return
