Neuromuscular Disorders Flashcards
upper motor neurons are contained in ______ and begin/end where?
contained within the CNS and begin in the cerebral cortex/end in vertebral horn of spinal cord
corticospinal tract
supplies
originates in
goes through which parts of brain
supplies voluntary muscles of trunk and extremities
originates in precentral gyrus
goes through internal capsule, midbrain, pons
corticospinal tract decussation details
75-90% decussate in medulla and form lateral corticospinal tract.
10-25% that do no decussate in medulla make up ventral corticospinal tract and travel to spinal cord. cross over before synapsing with lower motor neurons
corticospinal synapse with
spinal nerves
corticobulbar tract
supplies
originates in
involved in what kind of movements
supply voluntary muscles of head and follow corticospinal tract until they reach brainstem
originate in precentral gyrus next to lateral fissure of sylvius
precise motor movements
corticobulbar tract innervates these cranial motor nuclei bilaterally
3, 4, 6, 9, 10, 11
corticobulbar tract innervates these cranial motor nuclei unilaterally
7 (facial), 12 hypoglossal)
steps to neuromuscular junction synapses
- action potential arrives and initiates synaptic transmission
- sodium channels open, depolarizing axon terminal membrane
- depolarization of the terminal membrane causes VgCa channels to open
- calcium centers the cells and triggers fusion of Ach vesicles with presynaptic membrane
- Ach molecules diffuse across synaptic cleft and bind to receptors on postsynaptic membrane
- Ach receptors open chemically gated channels and depolarize postsynaptic membrane. this spreading depolarization fires an AP in postsynaptic membrane
- Ach in synaptic cleft is broken down by the enzyme acetylcholinesterase and the compounds are taken back up by the presynaptic cell for resynthesis
- after synaptic transmission, Ach and vesicles are recycled
where are lower motor neuron problems usually located
neuromuscular junction
upper motor neuron lesions (corticospinal, corticobulbar) sx
muscle groups are affected mild weakness minimal disuse muscle atrophy no fasciculations increased muscle stretch reflex hypertonia, spacticity pathological reflexes (positive babinski sign, toes flare out)
type of cells and location of upper motor neurons
pyramidal cells, motor cortex
lower motor neuron lesions sx
individual muscles may be affected mild weakness marked muscle atrophy fasciculations decreased muscle stretch reflex hypotonia, faccidity negative babinski sign
lower motor neurons are located in these two areas
ventral horn (spinal cord) and motor nuclei (brainstem)
lower motor neuron diseases that involve the bulbar region
bulbar palsies
ALS
lower motor neuron diseases that involve the myoneural junction
MG
5 diseases that involve upper motor neurons
cerebral palsy multiple sclerosis CVA parkinsons huntingtons
cerebral palsy definition
non progressive DO caused by injury or abnormal development in immature brain before, during, or after birth up to 1 year of age. damage or defects in corticospinal pathway
s/sx of CP (varies alot)
muscle weakness, loss of fine motor control
impaired speech
drooling
exaggerated deep tendon reflexes
spacticity
rigidity of extremities
scoliosis, contractures, joint dislocation (can get worse as they age)
CP associated problems
vision and hearing impairment swallowing problems seizures intellectual disability reflux disease abnormal pain perceptions
CP treatment
surgical (ortho, dental, general, opthomalogy, ENT) dorsal rhizotomy anti reflux operation intrathecal baclofen pumps botulinum toxin PT OT ST
dorsal rhizotomy for CP
tx muscle spasticity, cut nerves at root
botulinum toxin for CP
prevent release of Ach in NMJ to decrease spasticity
CP anesthesia considerations
hold preop sedatives and cautious with opioids (give short acting)
difficult vascular access (dehydrated, contracted)
difficult airway (dentition, secretions, TMJ ankylosis, contractures)
consider RSI*
succ does not produce risk of K increase but weight risk/benefit
cautious admin of NDMR (may be on anticonvulsants, resistant to NDMR’s)
decrease MAC need (20-30%)
prone to bleeding, hypothermia, intravascular depletion
slow emergences
careful with positioning (some may have scoliosis)
MS definition
autoimmune disease characterized by combination of demyelination, inflammation, and axonal damage of CNS. peripheral nerves are not affected. T cell mediated autoantibodies, demyelination. exacerbation and remission.
s/sx of MS
paresthesias (face, legs, arms, fingers) visual problems (optic neuritis and diplopia) muscle fatigue, weakness autonomic instability cognitive dysfunction (advanced stages) painful muscle spasms bulbar muscle dysfunction
MS includes which pathways
somatic motor
somatic sensory
autonomic
higher brain neurons
MS spares which nerves
peripheral
MS tx
decrease spasticity, tremors, bladder spasticity
diazepam, dantrolene, baclofen
glucocorticoids
immunosuppressants
CD20 monoclonal antibody interferon B1a or glatiramer acetate
situations that may exacerbate sx of MS
stress
increase body temperature
infection
hyponatremia
MS anesthetic considerations
avoid succ, scopolamine, atropine NDMR: use cautiously surgery avoided during flare avoid spinal block epidural safe to use aspiration risk increase risk of DVT stress dose steroids exaggerated hypotensive effects
CVA to anterior cerebral artery sx
contralateral leg weakness
CVA to middle cerebral artery sx
contralateral hemiparesis and hemisensory deficit (face and arm > leg)
aphasia
contralateral visual field deficit
CVA to posterior cerebral artery sx
contralateral visual field deficit and hemiparesis
CVA to penetrating arteries sx
contralateral hemiparesis
contralateral hemisensory deficits
CVA to basilar arteries sx
oculomotor deficits and/or ataxia
crossed sensory and motor deficits
CVA to vertebral artery sx
lower cranial nerve deficits
and/or ataxia with crossed sensory deficits
CVA tx
aspiring
TPA
surgery (crani/cerebellar resection)
anesthesia considerations for CVA
aspiration risk
DVT risk (bridging pt on anticoagulant therapy)
BG maintenance 20% of baseline
BP maintenance (dont rapidly drop BP. keep pressure up until revascularization where the surgeon will give you a range)
regional/MAC- reduce incidence of CVA
dysphagia may incite FVD
ASA theapy
CVA and coming back for another surgical procedure
need to restore auto regulation and vasomotor response to CO2. literature differs on 3 v 6 months
parkinson’s disease definition
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 extrapyramidal motor system and unopposed stimulation by Ach
s/sx of parkinson’s disease
skeletal muscle tremor (pill rolling, more prominent during rest and disappear during voluntary movement)
rigidity
akinesia (loss of voluntary movement)
diaphragmatic spasms
dementia
depression
facial immobility (infrequent blinking and paucity of emotional expressions)
parkinson’s disease tx
levodopa carbidopa (d carboxylase inhibitor) amandatine (antiviral, prolong QT) selegeline and rasagiline (avoid meperidine) surgery (DBS) ropinrole (dopa agonist) AchE (donepezil, tacrine) COMT inhibitors entacopine. (check liver enzymes) ARV: cimantadine (prolong QT)
parkinson’s disease anesthetic considerations
levodopa therapy continued hypotension and cardiac dysrhythmias avoid droperidol/haldol- antagonizes dopa aspiration HTN risk prone to post extubation laryngospasm avoid benzos sevo: agent of choice NMDB less effective of anticholinergics. use sugammadex
parkinson’s disease and ketamine
ok if patient on levodopa. if not, increased SNS response to ketamine
parkinsons and hyperdynamics
use direct acting for HoTN like neo versus indirect like ephedrine
huntingtons disease definition
degenerative disease of CNS characterized by marked atrophy of the caudate nucleus and to a lesser degree the putamen and globes pallid us
-autosomal dominant transmission with onset of 30-40 years
huntingtons disease sx
progressive dementia
chorea (involuntary jerking or writhing movements)
tremors
rigidity/contractures
depression, aggressive outburst, mood swings
difficulty with speech and swallowing (pharyngeal involuntary movement)
huntingtons disease tx
tx of choreiform movements (tremor/jerkins) with haldol or dopa antagonist/dopa store depletor
antidepressants
PT OT ST
huntingtons disease anesthetic considerations
aspiration risk (RSI) prolonged response to succ sensitive to NDMR consider avoiding reglan and anticholinergics glyco>atropine (BBB) autonomic dysfunction (labile BP)
lower motor neuron diseases
MG (lambert eaton) muscular dystrophy (duchenne, Becker) myotonic dystrophy mitochondrial DO gillian barre spinal muscular atrophy
myasthenia gravis definition
autoimmune destruction (IgG antibodies against the nicotinic acetylcholine receptor) or inactivation of postsynaptic acetylcholine receptors at the NMJ leading to reduced numbers of receptors and degradation of their function, and to complement mediated damage to postsynaptic end plate
MG s/sx
diplopia, ptosis fluctuating fatigue and weakness that improves after rest muscle weakness of mouth and throat dyspnea with exerrtion proximal muscle weakness
MG tx
cholinesterase inhibitor (physostigmine) plasmapharersis (r/t resp pharyngeal weakness) coticosteroids immunosuppressants, immunoglobins thymectomy
situations that exacerbate MG sx
pregnancy infection electrolyte imbalance surgical and psychological stress amino glycoside abx BB or higher doses of steroids (stress dose) can also exacerbate
MG anesthetic considerations
aspiration risk
sensitive NDMR “start small”
sensitive to respiratory deperssants
regional preferred (amide locals not esters)
avoid mid thoracic or inter scalene supraclavicula blocks
resistant to succinylcholine 2mg/kg
DOA of succ increases by 5-10 minutes (decreased functional Ach receptors)
volatiles OK, helps relax c/o or with less paralytics
regional still preferred
lambert eaton definition
presynaptic defect of 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 (males > females)
s/sx LEMS
proximal muscles mostly affected
weakness generally worse in morning and improves throughout the day
resp and diaphragm muscles become weka
ANS dysfunction: orthostatic hypotension, slowed gastric motility, urinary retention
begins in LE’s
dry mouth, impotence, small cell carcinoma
LEMS tx
3,4 DAP guanidine hydrochloride corticosteroids immunosuppressants plasmapharesis
LEMS anesthetic considerations
sensitive to succinylcholine and NDMR
inadequate reversal with AchE (if not on AchE agent like DAP)
high risk of postop respiratory failure
60% have small cell carcinoma
duchenne muscular dystrophy definition
most severe, dystrophin completely not working
x linked recessive DO that results from production of abnormal protein dystrophin. affects males > females and presents between 3-5 years of age and rarely lives past 30 years
s/sx duchennes
symmetric proximal muscle weakness that is manifested as a gait disturbance "gower sign" fatty infiltration typically causes enlargement of muscles, particularly the calves kyphoscoliosis resp muscle weakness degeneration of cardiac muscles impaired GI hypomotility impaired airway reflex impaired cardiac conduction cognitive impairment pulmonary HTN (as they progress) large tongue pseudo hypotonia of calves dont usually begin walking until about 18 months death is cardiopulmonary demise in 30's
becker muscular dystrophy defintion
dystrophin remains partially functioning
x linked recessive DO but less common (dystrophin lower)
sx 5-15 years
death is respiratory related in 4th-5th decade
becker muscular dystrophy s/sx
common to duchenne but usually present later in life and progress more slowly intellectual disability less common proximal muscle wekaness primininet calf pseudo hypertrophy degeneration of cardiac muscles
duchenne/becker MD dx
genetic testing CK levels (10-100x normal) muscle biopsy (rare)
duchenne/becker MD tx
surgery (ileus, scoliosis, contractures) PT steroids (can delay progression) biphosphates nystatin inhibitors gene modification protease inhibitors stem cell infusions
muscular dystrophy anesthetic considerations
association with MH (do TIVA, avoid succ)
preop medications with opioid and benzos should be avoided (NO VERSED)
intraop position complications due to kyphoscoliosis
sensitive to NDMR (prolonged 4x norm)
local and regional preferable (hard r/t scoliosis/contracture)
aspiration risk
dilated and hypertrophic cardiomyopathy
get echo, EEG, PFT’s
myotonic dystrophy definition
a hereditary degenerative disease of skeletal muscle that results in dysfunctional calcium sequestration by SR. sodium channel and chloride channel dysfunction is implicated as well. inability of skeletal muscle to relax. ex) grab door handle and cant let go
myotonic dystrophy s/sx
weakness: facial, thoracic, intercostal, diaphragm, sternocleidomastoid and distal limb inability to relax hand grip (myotonia) cardiomyopathy and conduction defects (1st degree AVB) dysphagia, slowed gastric emptying endocrine dysfunction central sleep apnea ptosis uterine atony in pregnant women
myotonic dystrophy triad in males
frontal balding, cataracts, testicular atrophy
myotonic dystrophy tx
procainamide phenytoin mexiletine baclofen dantrolene carbamazepine cardiac pacemaker
anesthetic considerations for myotonic dystrophy
avoid succinylcholine!!
aspiration risk
volatile anesthetics may produce exaggerated myocardial depression but high concentrations of volatile anesthetics may abolish myotonia. still questionable r/t MH
anesthesia and surgery could aggravate cardiac conduction problems by increasing vagal tone
neostigmine and physostigmine can aggravate myotonia
sensitive to respiratory depressant
maintain normothermia and avoid of shivering
PFT, ECG, trans thoracic pacing should be readily available
mitochondrial DO definition
heterogenous group of DO’s of skeletal muscle energy metabolism. mitochondria produce energy required by skeletal muscle cells through oxidation reduction reactions of electron transfer chain and oxidative phosphorylation thereby generating ADP
mitochondrial DO s/sx
abnormal fatiguability with sustained exercise “poor stamina”
skeletal muscle pain and progressive weakness
hearing loss, impaired vision
balance and coordination problems
seizures
learning deficits
organ problems
mitochondrial DO dx
hallmark: ragged red fiber
accumulation of mitochondria under sarcolemma, increased lactate to pyruvate ratio
mitochondrial DO tx
administration of metabolites and co factors
sodium bicarbonate/dichloracetate
ketogenic diet
anesthetic considerations mitochondrial DO
prone to acidoses and dehydration (first case)
lactate level
avoid propofol for continuous infusion (PRIS)
avoid succ and LR
maintain normothermia
use NDMR and LA’s with caution (sevo best)
avoid prolonged tourniquets
avoid bupivicaine
guillian barre definition
immunologic assault on myelin in peripheral nerves particularly lower motor neurons. action potential cannot be conducted, so motor endplate does not receive incoming signal. persist for 2 weeks and ends with full recovery in 4 weeks with some pernanent paralysis remaining
guillian barre s/sx
flaccid paralysis that begins in distal extremities and ascends bilaterlly
intercostal muscle weakness
facial and pharyngal weakness
sensory deficits
autonomic dysfunction common
paresthesias, impaired ventilation, hyperdynamic
guillcian barre tx
plasmapheresis (contradicted in active bleeding or dynamic instability)
IVIG: admin when you cannot do plasmapheresis
steroids are not useful
guillian barre anesthetic considerations
avoid succ****(K increase) sensitivity to NDMR increase risk of DVT risk of aspiration exaggerated response to indirect sympathomimetics (aline) SIADH possible, assess NA avoid rapid position changes avoid barbs/resp depressants/phenothiazines/CV depression MV risk postop
spinal muscular atrophy definition
due to deletions or mutations in survival motor neuron gene on chromosome 5q13. SMN gene product is involved in the formation of RNA complexes and their trafficking out of the nucleus. loss of SMN function promotes apoptosis of lower motor neurons. affect anterior horn of spinal cord
spinal muscular atrophy SMA I
infantile spinal muscular atrophy, an autosomal recessive DO that manifests usually within first 3 months of life. infants with this condition have difficulty sucking, swallowing, breathing. atrophy and fasciculation are found in tongue and limb muscles. disorder is rapidly progressive, leading to death from respiratory complications by age 3
spinal muscular atrophy SMA II
autosomal recessive mode of inheritance and begins in latter half of first year of life. it progresses more slowlyy than in infantile form, and patients may survive into adulthood
spinal muscular atrophy SMA III
juvenile form that develops after age 2. patients develop weakness of proximal limb muscles with relative sparing of bulbar muscles
spinal muscular atrophy tx
spinraza zolgensma evyrsdi PT surgery abx (low threshold with these patients)
spinal muscular atrophy anesthetic considerations
pulmonary consultation difficult intubation avoid succ** varying sensitivity to NDMR (longer DOA) regional (controversial) cautious with opioids postop resp support
ALS (upper and lower motor neurons) definition
rapidly progressive degeneration of motor neurons in corticospinal tract (directly to motor nerves, primary descending upper motor neurons) and the lower motor neurons in the anterior horn gray matter of the spinal cord. astrocytic gloss replaces affected motor neurons
ALS s/sx
spasticity hyperreflexia, loss of coordination muscle weakness fasciculations atrophy often begins in hands orthostatic hypotension resting tachycardia sensation remains intact
ALS tx
riluzole (NMDA receptor antagonist, only drug that reduces mortality)
edaravone (decrease decline in ADL’s)
smasmolytics
analgesics
ALS anesthetic considerations
avoid succ* increase sensitivity to NDMR aspiration risk consider postoperative mechanical ventilation increase sensitivity to resp depressants autonomic dysfunction with risk for hemodynamic instability spinal anesthesia avoided orthostatic hypotension and tachycardia PEA after induction a thing
