Spinal Cord Injury

Question 1

vertebral column

Answer 1

divided into vertebral bone segments fused together
protects the spinal cord
Cervical, thoracic, lumbar, and sacral spinal levels
an injury leads to loss of function of everything below the level it occurs at

Question 2

spinal nerves

Answer 2

run through the vertebra and correspond to the level of spinal cord
divided into different functions
cervical - vital autonomic functions
thoracic - regulating sympathetic nervous system
lumbar - lower body movements
sacral - sexual function

Question 3

dermatome

Answer 3

region of body surface that corresponds to a spinal segment - related to spinal nerves
strips of innervation and ennervation territory

Question 4

spinal cord

Answer 4

sensory input via dorsal roots
motor output via ventral roots
dorsal root ganglia contain cell bodies of sensory afferents

Question 5

nerve fibre tracts in spinal cord

Answer 5

descending:
- corticospinal tracts
- reticulospinal/vestibulospinal tracts
ascending:
- dorsal columns
- spinocerebellar tracts
- spinothalamic tracts

Question 6

dorsal columns

Answer 6

ascending tract - sensory info
touch, proprioception, vibration

Question 7

spinocerebellar tracts

Answer 7

ascending tract - sensory info
movement regulation
sense of balance - project to cerebellum

Question 8

spinothalamic tracts

Answer 8

ascending tract - sensory info
temperature + pain
neurons synapse with neurons in grey matter of dorsal horn → crossed pathway

Question 9

corticospinal tracts

Answer 9

descending - motor output
voluntary movement
finer movements

Question 10

reticulospinal/vestibulospinal tracts

Answer 10

descending - motor output
walking and posture
movement initiation
info comes from brain stem - reticular formation

Question 11

pain/temperature projection

Answer 11

crossed pathway = information enters spinal cord and makes connections to cell → axon immediately crosses over and ascends to thalamus and then projects to sensory cortex
(left side input → right side of spinal cord → right thalamus → right sensory cortex)

Question 12

touch/proprioception projection

Answer 12

ascends ipsilaterally = makes first synaptic contact in dorsal column → those nerves will then cross over to thalamus → sensory cortex
(left side input → left dorsal column nuclei → cross to right thalamus → right sensory cortex)

Question 13

muscle motor projection

Answer 13

info descends from motor cortex → crosses over to opposite side → spinal cord

left motor cortex controls right side motor actions

Question 14

Brown Sequard syndrome

Answer 14

lateral hemisection → impaired pain/temp on opposite side; impaired motor function + proprioception on same side

injury to left side interrupts the connection = no perception of pain/temp from right side; no movement or proprioception on left side

Question 15

spinal cord injury

Answer 15

most common = young men (16-30)
vehicle accidents, violence, falls, sports

injury rarely severs spinal cord; more commonly bruised, stretched, or compressed → crushed column - pieces break off and embed in tissue

Question 16

needs of SCI patients

Answer 16

freedom:
independent respiration
bladder/bowel function
sexual function
freedom from pain/spasms
arm/hand function
trunk posture
standing
walking

Question 17

ASIA classification of SCI

Answer 17

standard rating - allows assessment of deficits and remaining function
loss of sensory and motor function
5 levels: A = complete loss → E = normal function

Question 18

paraplegic

Answer 18

lower damage = impairment of legs, lower trunk, bladder + bowel, sexual function

Question 19

quadriplegic

Answer 19

partial or total loss of function in all limbs and torso
impairment of bladder, bowel, + sexual function
if injury to cervical level - impaired breathing

Question 20

additional complications

Answer 20

paralysis is immediate effect
1. hyperactive reflexes and spasms
2. autonomic dysreflexia
3. loss of bladder and bowel control
4. pressure ulcers
5. neuropathic pain

Question 21

Baclofen

Answer 21

administered intrathecally (into spinal canal) to reduce severe spasticity (or orally for mild)
GABA-B receptor agonist
increases presynaptic inhibition of transmission from sensory afferents

impaired descending inhibition column → add inhibition back

Question 22

autonomic dysreflexia

Answer 22

extended bladder activates sympathetic division of ANS → high blood pressure - not compensated for by central inhibition to heart = dangerous

descending brain activity regulation is impaired

can treat by interrupting control to inhibitory systems to shut off SNS and get PNS

Question 23

loss of bladder and bowel control

Answer 23

coordination of autonomic and somatic responses required neural networks in brain stem

stretch of bladder activates afferents → signal to PNS to contract bladder
sphincter muscles cannot be uninhibited because there is no brain signal

Question 24

immediate treatments for SCI

Answer 24

1. immobilization - prevent further damage
2. spinal surgery to decompress cord - return to normal alignment
3. drugs to reduce inflammation - cascade effect on nearby cells can be prevented
4. rehabilitation - retraining motor circuits

Question 25

secondary damage in SCI

Answer 25

increase in cell death and demyelination following initial injury
wave of inflammation/cascade to cells in surrounding tissues
- ischemia (reduced oxygen)
- edema (swelling)
- glutamate increase (cell death causes burst of excitation)
- BBB breakdown (trauma)
- inflammation (invasion from macrophages; activation of microglia)

Question 26

rhythmic networks in spinal cord

Answer 26

electrical stimulation of spinal cord in SCI patient evokes rhythmic activity in leg muscles

spinal cords have inherent rhythmicity → use central pattern generators to trigger
movement by bypassing brain

Question 27

rehab therapies

Answer 27

treadmill therapy - improve walking
LOCOMAT

Question 28

future possibilities

Answer 28

goal: repair damage + enhance plasticity of undamaged neurons → grow new connections from existing

Question 29

axons in CNS

Answer 29

damaged axons in CNS do not regenerate
1. growth inhibitors on CNS myelin = limit to prevent uncontrollable growth
2. mechanical barriers = form after injury to protect area

Question 30

glial scar

Answer 30

glial cells from scar around injury site
serves protective function - damage can’t spread
axon cannot regrow on glial scar

Question 31

treatment strategies

Answer 31

1. promote regeneration of damaged axons
   - block growth inhibitory molecules
   - bridge damaged regions
   - digest scar tissue
2. enhance function of existing nerve cells
   - remyelinate axons

Question 32

growth inhibitory molecules

Answer 32

myelin: - Nogo-A, MAG, OMgp
CSPGs
any growth will retract backwards from molecules

apply antibodies to block inhibitors on myelin or their receptors on growth cones

Question 33

CSPGs

Answer 33

chondroitin sulfate proteoglycan
part of extracellular matrix
main growth inhibitor

Question 34

bridging lesion

Answer 34

• mechanical bridges
• Schwann cells - myelin-producing cells in periphery
• olfactory ensheathing cells - glia from olfactory bulb; promotes axon growth (like stem cells)
• stem cells - produce growth promoting environment

Question 35

digest scar tissue

Answer 35

CSPG is upregulated after injury by astrocytes
applying enzyme chondriotinase will cut CSPG in particular sites so axons can grow through

Question 36

remyelination of axons

Answer 36

use stem cells to produced oligodendrocytes - glial cells
will remyelinate damaged axons + improve residual function