Neuro 57: Spasticity and muscle relaxants

Question 1

What are the 7 UMN disorders that cause spasticity?

Answer 1

1. stroke = most common
2. cerebral palsy
3. traumatic brain injury
4. MS
5. spinal cord injury
6. spinal cord compression
7. ALS

Question 2

Baclofen: MOA & uses

Answer 2

• GABA agonist for spinal neurons –> causes hyperpolarization in the primary efferent fibers
• used as a CNS muscle relaxant
• also use in the tx of trigeminal neuralgia

Question 3

Baclofen: precautions

Answer 3

-becareful using if the pt has renal impairment or a hx of seizures

Question 4

Baclofen: adverse rxns

Answer 4

• drowsiness, vertigo, psychiatric disturbances, insomnia, slurred speach, ataxia, hypotonia, wkness

Question 5

Tizanidine: MOA & uses

Answer 5

• alpha-2-adernergic agonist
• causes decreased excitatory input to the alpha motor neurons (centrally acting)
• CNS muscle relaxant

Question 6

Tizanidine: precautions

Answer 6

-be careful when using in pts with hepatic or renal impairment

Question 7

Tizanidine: adverse rxns

Answer 7

• hypotension, somnolence, xerostomia, wkness
• encephalopathy –> esp in elderly!
• orthostatic intolerence –> b/c loose the baroflex rxn!

Question 8

Cyclobenzaprine: MOA & uses

Answer 8

• serotonin and NE uptake inhibitor –> similar to tricyclic antidepressants
• reduceds excitatory input to aplha and gamma mn
• wker CNS muscle relaxant, so used more for ppl with stiff muscles rather than spasticity

Question 9

Cyclobenzapine: precautions

Answer 9

-be careful when using in pts with hepatic impairment or using MAO-B inhibitors

Question 10

Cyclobenzapine: adverse rxns

Answer 10

-drowsiness, dizziness, xerostomia

Question 11

Benzodiazepines: MOA & use

Answer 11

• GABA agonist

- CNS muscle relaxant

Question 12

Benodiazepines: adverse rxns

Answer 12

-sedation, ataxia, dysarthria, diplopia, constipation, diarrhea, nausea, dry mouth, urinary retention

Question 13

Dantrolene: MOA & uses

Answer 13

• presents the release of Ca from the SR in myocytes

- PERIPHERALLY acting muscle relaxant

Question 14

Dantrolene: adverse rxns

Answer 14

• hepatotoxicity –> so usually a drug of last resort!

- muscle cramps & wkness

Question 15

Maligant hyperthermia

Answer 15

• rare
• life threatening
• due to exposure of gas anesthetics or succinylcholine –> causes a massive influx of Ca into the myocytes –> muscle depolarization –> hypercatabolic state –> fever, tachy, metabolic acidosis, rhadbomyolysis, & circulatory collapse
• due to a mutation in ryanodine receptor (autosomal dominant) OR an underlying myopathy

Question 16

4 step Tx for malignant hyperthermia

Answer 16

1. remove the offending agent
2. tx the metabolic abnormalities
3. IV hydration
4. Dantrolene IV

Question 17

Botulinum toxin: MOA

Answer 17

• interferes with several proteins at the presynaptic membrane –> prevents the release of NTs
• needs to be injected every 3 mnths

Question 18

Botulinum toxin: adverse rxns

Answer 18

• depends on where it is injected

- can include: pain, wkness, dysphagia, ptosis, xerostomia

Question 19

Tx of significant lower extremity spasticity

Answer 19

-does not respond well to oral rx –> better to use intrathecal baclofen (=pump)

Question 20

Tx of significant upper extremity spasticity

Answer 20

-does not respond well to oral rx –> use botox injections!