spinal cord injury 12 - spasticity
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muscle tone def
resting tension in a muscle evidenced by resistance to enlongation due to joint movement
balance of excitatory and inhibitory influences on the spinal motor neuron innervating the muscel
elastic properties of the muscle itself
3 elements of the neuropath behind spasticity
- UMN lesion or lesion to descending pathways
- loss of modulation to spinal reflexes
- increased responiveness to afferent input
monosynaptic stretch reflex (MSR)
single synapse between the afferent and efferent limb of the reflex arc -- it's the fastest response in the nervous system
def of spasticity and some nicknames
- increased responsiveness of the monosynaptic stretch reflex (or a velocity dependant reaction to stretch)
- aka - DTR, Ia reflex, phasic reflex
spasticity is velocity dependent reaction to stretch but can also be due to these afferent inputs...
- skin touch
- pin prick (deformation of tissue give sensory input which leads to motor output)
- hair pull
stress and fatigue can also stim this
for whom is spasticity more problematic?
incomplete > complete
why is spasticity more problematic in incomplete than complete SCIs?
remaining intact supraspinal descending inputs are no longer appropriate for reorganized spinal circuits --> greater motor dyscontrol
sad spiral of spasticity
as an agonist becomes spastic it resists stretching, so the tendon shortens, further resisting stretch ... so, got to maintain muscle range!
what percent of SCIs report spasticity in frist year? what percent say it's problematic?
- 30-40%, esp in cervical SCIs
when will you see flacid paralysis in SCI?
- spinal shock
- damage to peripheral nerves
basic scoring of the Modified Ashworth Scale
- 0 = no increase in tone
- 1 = catch and release
- 1+ = cathc and then minimal resistance
- 2 = resistance thru range, but movable
- 3 = considerable resistance in range
- 4 = can't move, rigid
MAS pros and cons
- pros: intra and inter-rater reliability
- cons: only tests passive movement, only tests extremities and not trunk, doesn't account for effects of position or exertion, range is measured so contractures can --> false positives
Tartdieu scale for spasticity
- (used in research, but he doesn't know people who use it in practice)
- test movement at 3 speeds: V1 = slower than gravity, V2 = gravity, V3 = faster than gravity
- rate it 0=5 for resistance, clonus, immovable
pendulum test for spasticity
pt supine, leg off table, you drop the pt's leg and note where it reverses/bounces up/switces from flexing to extending
silly test bc it's so unfunctional -- if you treated based on this you'd be treating the impairment, not the fxn
Spinal Cord Assessment Tool for Spastic Reflexes (SCATS)
looks at reflex respons to stim (pinprick, rapid flexion) -- doesn't look at spasticity in response to functional movement, onloy looks at ankle clonus, flexor reflex, and extensor reflex in the LE
Penn Spasm Frequency scale measures...
# of muscle spasms / hour
Snow Spasme Frequency scale measures...
- # spasms / day
- (problem - this assumes that the # is what's problematic, doesn't record severity, is self reported)
24hr EEG for spasticity?
feh - only works if spasms are in cortex, not spinal cord
spasm vs spasticity
- spasm = twitch
- spasticity = an increase in resistance to sudden , passive movement and IS velocity dependent. The faster the passive movement the stronger the resistance.
Sahrman & Norton's philosphy on how to treat spasticity
they say spasticity is more a problem of agonist weakness than antag spasticity (it's a problem of decreased descending drive rather than resistance from the spastic antagonist, that's the primary factor limiting vol mvmnt)
sooo, treat it by strengthening the muscle opposite to the spastic muscle... may help, may lead to increased spasticity
how does stretching fight spasticity?
- reduces the H-reflex in the able bodied (that's the measure of excitability of the MSR/monosynaptic stretch reflex)
- prevents loss of sarcomees
- prevents buildup of connective tissue
- maintains ROM
serial casting to treat spasticity?
- prolonged stretching, w new cast increasing the ROM weekly
- often paired w chemodenervation
which drug treats spasticity at spinal origin?
- baclofen - max doese: 80-100 mg
- side effects: drowsiness, lethargy
which drugs target reducing pain from spasticity?
tizanidine, clonidine - act at CNS
which drug for spasticity acts at the level of the contractile unit, not the CNS?
- (but like the others, will have global effects)
- injection of phenol or alcohol blocks
- acts at level of peripheral nerve
- it dissolves the myelin sheath so the nerve goes flacid and the muscles contoled by that nerve turn off, so you can strengthen the agonist, fight contracture -- kind of a reset button ...may/maynot fix spasticity... neuroplasticity may help
botox's role in battling spasticity?
- inhibits acetylcholine release at neuromuscular junction
- works at level of individual (big or small) muscle
- UE > LE better responses
which spasticity drug works at level of individual muscle?
- botox -- it inhibits acetylcholine release at NMJ
- can be used for big or small muscles, but is more effective UE>LE
what to do if spasticity is refractory to oral meds?
- intrathecal baclofen
- (it's a neurosurgical procedure allowing for calibration of dosage for specific times. Measured in micrograms, rather than the milligrams of oral baclofen -- replaced 5-7 yrs)
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