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N935 Advanced Pathophysiology II > Neuromuscular Disorders > Flashcards

Neuromuscular Disorders Flashcards

1
Q

neuromuscular diseases

A

disorders that adversely affect muscle function either primarily or via nerve or neuromuscular junction abnormalities

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2
Q

upper motor neurons

A
  • motor pathways completely contained within the CNS
  • begin in the cerebral cortex and end in the ventral horn of the spinal cord
  • generally form synapses with interneurons which then form synapses with lower motor neurons before projecting to the periphery
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3
Q

primary roles of upper motor neurons

A

-directing, influencing, and modifying reflex arcs, lower-level control centers and motor neurons and some sensory

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4
Q

corticospinal tract

A
  • supply the voluntary muscles of the trunk and extremities
  • synapses with SPINAL nerves
  • originates in precentral gyrus
  • goes through the internal capsule, midbrain and pons
  • two tracts come from this –> lateral corticospinal and ventral corticospinal
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5
Q

lateral corticospinal tract

A
  • 75-90% of neurons from corticospinal tract
  • decussate in medulla
  • each cord level, fibers leave and enter ventral horn to synapse with lower neurons
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6
Q

ventral corticospinal tract

A
  • 10-25% that of neurons from corticospinal tract
  • do NOT decussate in the medulla
  • travel to spinal cord
  • decussate before synapsing with lower motor neurons
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7
Q

corticobulbar tract

A
  • supply the voluntary muscles of the head and follow the corticospinal tract until they reach the brainsetm
  • synapses with CRANIAL nerves
  • originate in the precentral gyrus next to the lateral fissure of Sylvius
  • innervates cranial motor nuclei III, IV, VI, IX, X and XI bilaterally
  • involved in precise motor movements
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8
Q

which cranial nerves does the corticobulbar tract not innervate bilaterally

A
  • facial VII

- hypoglossal XII

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9
Q

lower motor neuron functions

A
  • neurons located in brainstem or spinal cord
  • responsible for direct influence on muscles
  • send axons out through nerves in PNS to synapse on and control skeletal muscle cells
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10
Q

lower motor neurons that pass through spinal nerves

A

control muscles of the limbs and trunk

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11
Q

lower motor neurons that pass through cranial nerves

A

control skeletal muscles of the head and neck

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12
Q

neuromuscular junction (NMJ)

A
  • AP arrives an initiates synaptic transmission
  • Na+ channels open, depolarizing axon terminal membrane
  • depolarization of terminal causes VG-Ca2+ channels to open
  • calcium enters cell and triggers fusion of vesicles filled with ACh to presynaptic membrane
  • ACh diffuses across synpatic cleft and binds with nAChR on post-synaptic membrane
  • nAChR oepn, Na+ floods in, depolarizing postsynaptic membrnae
  • spreading depolarzation fires AP in post-synaptic membrane
  • ACh broken down by acetylcholinesterases and components taken back up by presynaptic cell to reuse
  • after synaptic transmission ACh and vesciles recycled
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13
Q

UMN lesions (pyramidal cells of motor cortex)

A
  • corticospinal and corticobulbar
  • muscle groups are affected
  • mild weakness
  • minimal disuse muscle atrophy
  • no fasiculations
  • increased muscle stretch reflex
  • hypertonia
  • spasticity
  • pathological reflexes
  • positive babinski
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14
Q

LMN ventral horn (spinal cord) and motor nuclei (brainstem) lesions

A
  • individual muscles may be affected
  • mild weakness
  • marked muscle atrophy
  • fasiculations
  • decreased muscle stretch reflex
  • hypotonia
  • flaccidity
  • no babinski sign
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15
Q

UMN diseases

A
  • cerebral palsy
  • multiple sclerosis
  • cerebrovascular accident
  • parkinson’s
  • huntington’s
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16
Q

cerebral palsy

A
  • non-progressive disorder caused by injury or abnormal development in the immature brain before, during or after birth up to 1 year of age
  • damage that affects the corticospinal pathway
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17
Q

S/S cerebral palsy

A
  • symptoms are very heterogenous
  • muscle weakness, loss of fine motor control
  • impaired speech
  • drooling
  • exaggerated deep tendon reflexes
  • spasticity
  • rigidity of extremities
  • scoliosis, contractures, joint dislocation
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18
Q

associated problems with cerebral palsy

A
  • vision and hearing impairment
  • swallowing problems
  • seizures
  • intellectual disability
  • reflex disease
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19
Q

CP treatment

A
  • no cure, treat symptoms to help increase ADLs
  • surgical - ortho, dental, general, opthomology, ENT; dorsal rhizotomy (to treat muscle spasticity), antireflux operation, intrathecal baclofen pumps
  • medications - botulinum toxin
  • physical and occupational therapy
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20
Q

CP anesthetic considerations

A
  • hold pre-op sedatives and caution with opioids
  • difficult IV access
  • difficult airway (dentition, increased secretions, TMJ ankylosis, contractures)
  • consider RSI (secretions etc)
  • succ does not produce increase K release
  • caution in admin of NDMR (some anticonvulsant may interact and make more resistant to NDMRs)
  • decreased MAC need (20-30%)
  • prone to bleeding, hypothermia, and intravascular depletion
  • slow emergences
  • caution with positioning
  • regional = difficult
  • increase chance of latex allergy
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21
Q

multiple sclerosis

A
  • autoimmune disease characterized by combination of demyelination, inflammation and axonal damage of the CNS
  • peripheral nerves not affected
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22
Q

multiple sclerosis S/S

A
  • paresthesias - face, legs, arms, fingers
  • muscle fatigue/weakness
  • painful muscle spasms
  • visual problems (optic neuritis and diplopia)
  • autonomic instability
  • bulbar muscle dysfunction
  • cognitive dysfunction (ADVANCED stages)
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23
Q

MS treatment

A
  • decrease spasticity, tremors, and bladder spasticity
  • diazepam, dantrolene, or bacloflen
  • glucocorticoids
  • immunosuppressants
  • CD20 monoclonal antibody, interferon B1a or glatiramer acetate
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24
Q

MS situations that exacerbate the symptoms

A
  • stress
  • increase body temperature
  • infection
  • hyponatremia
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25
Q

MS anesthetic considerations

A
  • avoid succinylcholine, scopolamine, atropine
  • NDMR - use cautiously
  • surgery avoided during flare
  • avoid spinal block
  • epidural safe
  • aspiration risk
  • increased risk of DVT
  • stress dose steroids
  • exaggerated hypotensive effects
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26
Q

cerebrovascular accident

A

stroke is characterized by sudden neurologic deficits resulting from ischemia (88% of cases) or hemorrhage (12% of cases)

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27
Q

anterior cerebral artery

A

contralateral leg weakness

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28
Q

middle cerebral artery

A
  • contralateral hemiparesis and hemisensory deficit (face & arm > leg)
  • aphasia
  • contralateral visual field deficit
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29
Q

posterior cerebral artery

A

contralater visual field deficit and hemipareis

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30
Q

penetrating arteries

A
  • contralateral hemiparesis

- contralateral hemisensory deficits

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31
Q

basilar artery

A
  • oculomotor deficits and/or ataxia

- crossed sensory and motor deficits

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32
Q

vertebral artery

A
  • lower cranial nerve deficits

- and/or ataxia with crossed sensory deficits

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33
Q

CVA treatment

A
  • aspirin
  • TPA (IV or direct infusion right into area where the clot is)
  • surgery (crani/cerebellar resection)
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34
Q

CVA anesthetic considerations

A
  • aspiration risk
  • DVT risk
  • BS maintenance
  • BP maintenance (because want to maintain CPP and not worsen ischemia)
  • avoid –> hyperglycemia, dehydration, hyperthermia, infections
  • regional/MAC –> decreased incidence of stroke and less swings in BP
  • statins
  • aspirin therapy
35
Q

when are patients with a CVA allowed to come back in for elective surgery?

A
  • controversial
  • 3-6 months
  • need to to restore –> autoregulation and vascular response to CO2
  • this is why it is important to ask your patient WHEN the had a stroke
36
Q

parkinson’s disease

A
  • neurodegenerative disorder of unknown cause marked by a characteristic loss of dopaminergic fibers in the basal ganglia
  • regional dopamine concentrations are also depleted
  • depletion of dopamine results in diminished inhibition of neurons controlling the extrapyramidal motor system and unopposed stimulation by ACh
37
Q

S/S parkinson’s disease

A
  • skeletal muscle tremor (pill-rolling, more prominent during rest and disappears during voluntary movement)
  • rigidity
  • alkinesia (loss of ability to perform voluntary movement)
  • diaphragmatic spasms
  • dementia
  • depression
  • facial immobility (infrequent blinking and paucity of emotional expressions)
38
Q

parkinson’s disease treatment

A
  • GOAL = increase dopamine in basal ganglia
  • levodopa
  • carbidopa
  • ACh inhibitors
  • dopa agonist
  • amantadine
  • selegiline (check BG, may have serotonin syndrome) and rasagiline
  • surgery (DBS)
  • COMT inhibitors
  • antivirals (prolong QT)
39
Q

parkinson’s disease anesthetic considerations

A
  • levodopa therapy continued
  • hypotension and cardiac dysrhythmias (droperidol/Haldol)
  • aspiration risk
  • airway risk
  • HTN risk
  • prone to post-op laryngospasm
  • avoid benzodiazepines
  • sevoflurane = agent of choice; avoid iso because may exacerbate disease; des wont hurt but sevo is BEST
  • NMBD less effective if patient on anticholinergic for dementia (use sugammadex)
  • ketamine = controversial
  • succ also controversial because hyperkalemia (individual patient to patient basis)
40
Q

huntington’s disease

A

degenerative disease of the CNS characterized by marked atrophy of the caudate nucleus and to a lesser degree the putamen and globus plaaidus

  • autosomal dominant
  • delayed –> onset of symptoms at 35-40 years
  • usually 17 year duration from onset of disease to death
41
Q

huntington’s disease S/S

A
  • progressive dementia
  • chorea (involuntary jerking or writing movements)
  • tremors
  • rigidity/contractures
  • depression, aggressive outburst, mood swings
  • difficulty with speech and swallowing
42
Q

huntington’s disease treatment

A
  • treat choreiform movements (usually with haldol or keppra)
  • antidepressants
  • physical, occupational, and speech therapy
43
Q

huntington’s disease anesthetic considerations

A
  • aspiration risk
  • prolong response to succinylcholine
  • sensitive to NDMR
  • consider avoiding reglan and anticholinergics (glyco > atropine)
  • difficult IV access because jerky movements
  • autonomic dysfunction (labile BP)
  • regional - you can, but difficult because jerky movements
44
Q

LMN diseases

A
  • myasthenia gravis
  • LEMS
  • muscular dystrophy (Duchenne + Becker)
  • myotonic dystrophy
  • mitochondrial disorder
  • guillain barre
  • spinal muscular atrophy
45
Q

myasthenia gravis

A
  • autoimmune destruction or inactivation of nAChR at the neuromuscular junction leading to reduced numbers of receptors and degradation of their function, and to complement mediated damage to the post-synaptic end plate
  • autoimmune destruction = IgG antibodies against nAChR
46
Q

myasthenia gravis S/S

A
  • diplopia, ptosis
  • fluctuating fatigue & weakness that improves after rest
  • muscle weakness of mouth and throat
  • dyspnea with exertion
  • proximal muscle weakness
47
Q

myasthenia gravis treatment

A
  • cholinesterase inhibitor (pyridostigmine)
  • plasmapheresis
  • corticosteroids
  • immunosuppressants, immunoglobins
  • thymectomy
48
Q

myasthenia gravis situations that exacerbate symptoms

A
  • pregnancy
  • infection
  • electrolyte imbalance
  • surgical and physchological stress
  • aminoglycoside antibiotics
49
Q

myasthenia gravis anesthetic considerations

A
  • aspiration risk
  • sensitive to NDMR
  • sensitive to respiratory depressants
  • regional preferred (but with amides not esters!!!)
  • avoid mid thoracic or interscalane or supraclav blocks (because DONT want phrenic nerve palsy already weak)
  • resistant to succinylcholine (2 mg/kg), DOA increased by 5-10 min
  • volatiles no known concerns and helps with muscle relaxation
50
Q

LEMS

A

presynaptic defect of the neuromuscular transmission in which antibodies to voltage gated calcium channels on the nerve terminal markedly reduce the quantal release of ACh at the motor end plate

51
Q

LEMS S/S

A
  • proximal muscles mostly affected (begins in limbs and spreads up)
  • weakness generally worse in AM and improves through the day (because exercise increases calcium so increased ACh released from vesicles)
  • respiratory and diaphragm muscles become weak
  • ANS dysfunction - orthostatic hypotension, slowed gastric motility, urinary retention
52
Q

LEMS treatment

A
  • 3,4 -DAP
  • guanidine hydrochloride
  • corticosteroids
  • immunosuppressants
  • plasmapheresis
  • sometimes AChEi but not a lot of people
53
Q

LEMS anesthetic considerations

A
  • sensitive to succ and NDMR
  • inadequate reversal with anticholinesterase
  • high risk of post-op resp. failure
  • 60% have small cell carcinoma
54
Q

Duchenne muscular dystrophy

A
  • x-linked recessive disorder that results from production of abnormal protein dystrophin
  • affects males>females
  • presents between 3-5 years of life
  • rarely live past 30 (death due to cardiopulmonary demise)
55
Q

Duchenne muscular dystrophy S/S

A
  • symmetric proximal muscle weakness that is manifested as gait disturbance (Gower sign)
  • fatty infiltration typically causes enlargement of muscles, particularly calves
  • kyphoscoliosis
  • respiratory muscle weakness
  • degeneration of cardiac muscles
  • impaired GI hypomotility
  • impaired airway reflex
  • impaired cardiac conduction
  • cognitive impairment
  • pulmonary hypertension
56
Q

becker muscular dystrophy

A
  • x-linked recessive disorder but less common

- dystrophin lower; retains partial function un like Duchennes so S/S usually less severe

57
Q

becker muscular dystrophy S/S

A
  • common to Duchenne except that they usually present later in life (adolescence) and progress more slowly
  • intellectual disability less common
  • proximal muscle weakness
  • prominent calf pseudohypertrophy
  • degeneration of cardiac muscles
58
Q

Duchenne/becker muscular dystrophy diagnosis

A
  • genetic testing
  • CK levels
  • muscle biopsy
59
Q

Duchenne/becker muscular dystrophy treatment

A
  • surgery
  • PT
  • steroids
  • biophosphates
  • mystatin inhibitors
  • gene modification
  • protease inhibitors
  • stem cell infusions
60
Q

Duchenne/becker muscular dystrophy anesthetic considerations

A
  • association with MH (TIVA) –> avoid succ and volatiles
  • preoperative pre mediations with opioid and benzo should be avoided
  • intraop position complications due to kyphoscoliosis
  • sensitive to NDMR (prolonged up to 4x)
  • local and regional preferable
  • aspiration risk
  • ECHO, EKG, LFTs
61
Q

myotonic dystrophy

A
  • hereditary degenerative disease of skeletal muscle that results in the dysfunctional calcium sequestration by the SR
  • sodium and chloride channel dysfunction is implicated as well
62
Q

myotonic dystrophy S/S

A
  • weakness - facial, thoracic, intercostal, diaphragm, sternocleidomastoid, & distal limb
  • inability to relax hand grip (myotonia)
  • cardiomyopathy
  • conduction defects (1st degree AV block)
  • dysphagia, slowed gastric emptying
  • endocrine dysfunction
  • central sleep apnea
  • ptosis
63
Q

myotonic dystrophy triad in males

A
  • frontal balding
  • cataracts
  • testicular atrophy
64
Q

myotonic dystrophy treatment

A
  • procainamide
  • phenytoin
  • mexiletine
  • baclofen
  • dantrolene
  • carbamazepine
  • cardiac pacemaker
65
Q

myotonic dystrophy anesthetic considerations

A
  • avoid succ (incidence of complete jaw lock)
  • aspiration risk
  • volatiles = may produce exaggerated myocardial depression, high concentrations of volatiles can abolish myotonia; questionable though because of association with MH
  • anesthesia and surgery could aggravate cardiac conduction problems by increasing vagal tone
  • neostigmine and physostigmine can aggravate myotonia
  • sensitive to resp depressant
  • maintain normothermia and avoid shivering
  • PFTs, EKG, transthoracic pacing readily available
66
Q

mitochondrial disorders

A
  • group of heterogenous disorder of skeletal muscle energy metabolism
  • mitochondria produce energy required for skeletal muscle cells through oxidation-reduction reactions of ETC and oxidative phosphorylation thereby generating ADP
67
Q

mitochondrial disorders S/S

A
  • abnormal fatigability with sustained exercise
  • skeletal muscle pain and progressive weakness
  • hearing loss, impaired vision
  • balance and coordination problems
  • seizures
  • learning deficits
  • organ problems (heart, liver, kidney, brain)
68
Q

mitochondrial disorders treatment

A
  • treat symptoms
  • administer metabolites and cofactors
  • sodium bicarb and dichloroacetate
  • keto diet
69
Q

mitochondrial disorders anesthetic considerations

A
  • prone to acidosis and dehydration (make them 1st case to avoid this)
  • lactate level
  • avoid prop for continuous infusion (PRIS)
  • avoid succ and LR
  • maintain normothermia
  • use LA and NDMR with caution
  • avoid prolonged tourniquets
  • avoid bupivacaine
70
Q

guillain-barre

A
  • immunologic assault on myelin in the peripheral nerves particularly lower motor neurons
  • AP cannot be conducted, so motor endplate does not receive the incoming signal
  • persist for 2 weeks and ends with full recovery in 4 weeks with some permanent paralysis remaining
71
Q

guillain-barre S/S

A
  • flaccid paralysis that begins in distal extremities and ascends bilaterally
  • intercostal muscle weakness
  • facial and pharyngeal weakness
  • sensory deficits
  • autonomic dysfunction common
72
Q

guillain-barre treatment

A
  • plasmapheresis
  • IVIG
  • steroids NOT useful therapy
73
Q

guillain-barre anesthetic implications

A
  • avoid succ
  • sensitive to NDMR
  • increased risk DVT
  • risk of aspiration
  • exaggerated response to indirect sympathomimetics (a line)
  • increased incidence of SIADH (check sodium)
  • slow position changes due to hemodynamic instability
  • respiratory depression common
  • do well with general or spinal but NOT both together
74
Q

spinal muscular atrophy (SMA)

A
  • SMA due to deletions or mutations in the survival motor neuron gene on chromosome 5q13
  • SMN gene product involved in formation of RNA complexes and their trafficking out of the nucleus
  • loss of SMN function promotes apoptosis of LMNs
  • affect anterior horn of spinal cord
75
Q

SMA I

A
  • infantile
  • autosomal recessive disorder
  • manifests usually in first 3 months of life
  • infants have difficulty sucking, swallowing, and breathing
  • atrophy and fasciculation are found in tongue and limb muscles
  • disorder is rapidly progressive, leading to death from respiratory complications usually by 3 yo
76
Q

SMA II

A
  • autosomal recessive
  • begins in latter half of first year of life
  • progresses more slowly than infantile form, patients may survive into adulthood
77
Q

SMA III

A
  • juvenile form
  • develops after age 2
  • patients develop weakness of proximal limb muscles with relative sparing of bulbar muscles
78
Q

SMA treatment

A
  • spinraza, zolgensma, evrysdi
  • PT
  • surgery
  • abx - give quickly usually
79
Q

SMA anesthetic considerations

A
  • pulmonary consultation
  • difficult intubation
  • avoid succ
  • varying sensitivity to NDMR (longer DOA)
  • regional is controversial (neuraxial difficult and unreliable in these patients)
  • caution with opioids (resp depression)
  • post-op resp support usually required
80
Q

amyotrophic lateral sclerosis (ALS)

A
  • rapidly progressive degeneration of motor neurons in the corticospinal tract (primarily descending upper motor neurons) and the lower motor neurons in the anterior horn gray matter of the spinal cord
  • astrocytic gliosis replaces the affected motor neurons
  • males aged 40-60
  • cause is unknown
81
Q

ALS S/S

A
  • spasticity
  • hyperreflexia, loss of coordination
  • muscle weakness
  • fasciculations
  • atrophy often begins in hands
  • orthostatic hypotension
  • resting tachycardia
  • sensations remain intact (including cognition and usually bladder/bowel function)
82
Q

ALS treatment

A
  • riluzole (NMDA receptor antagonist); only drug that reduces mortality
  • edaravone (decreases decline in ADLs)
  • spasmolytics
  • analgesics
83
Q

ALS anesthetic considerations

A
  • avoid succ
  • increased sensitivity to NDMR
  • aspiration risk
  • consider post-op mechanical ventilation
  • increase sensitivity to respiratory depressants
  • autonomic dysfunction with risk for hemodynamic instability
  • spinal anesthesia avoided

N935 Advanced Pathophysiology II (16 decks)

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