neuromuscular diseases Flashcards
What are neuromuscular diseases?
disorders that adversely affect muscle function either primarily or via nerve or neuromuscular junction abnormalities
upper motor neurons are
completely contained within the CNS
where do upper motor neuron pathways being and end?
begin: cerebral cortex
end: ventral horn of the spinal cord
primary roles of upper motor neurons
directing, influencing, and modifying reflex arcs, lower level control centers and motor neurons and some sensory
upper motor neurons form
synapses with interneurons which then form synapses with lower motor neurons before projecting to the periphery
the corticospinal tract supplies the
voluntary muscles of the trunk and extremities
where does the corticospinal tract originate?
precentral gyrus
75-90% of the corticospinal tract decussates in the ___ and forms the ____
medulla; lateral corticospinal tract
10-25% of the corticospinal tract makes up the ____
ventral corticospinal tract and travel to the spinal cord
the corticobulbar tract supplies the
voluntary muscles of the head and follow the corticospinal tract until they reach the brainstem
where does the corticobulbar tract originate
in the precentral gyrus next to the lateral fissure of Sylvius
the corticobulbar tract innervates cranial motor nuclei _____ bilaterally except
III, IV, VI, IX, X, XI; except facial and hypoglossal
the corticobulbar tract is involved in
precise motor movements
lower motor neurons are located in
the brain stem or in the spinal cord
the lower motor neurons are responsible for
direct influence on muscles
lower motor neurons send axons out through nerves in the ____ to synapse on and control ____
peripheral nervous system; skeletal muscle cells
the lower motor neurons that pass through the spinal nerves primarily control
muscles of the limbs and the trunk
lower motor neurons that pass through cranial nerves primarily control
the skeletal muscles of the head and the neck
What happens when an action potential arrives and initiates synaptic transmission at the neuromuscular junction
Na+ channels open depolarizing the axon terminal causing VG Ca++ channels to open allowing Ca++ to enter the cell and vesicles to fuse and release ACh into the synaptic cleft, the ACh will bind to receptors on the postsynaptic membrane opening nAChR channels and depolarize the membrane
ACh in the synaptic cleft is broken down by
acetylcholinesterase
upper motor lesion characteristics
muscle groups are affected mild weakness minimal disuse muscle atrophy no fasciculations increased muscle stretch reflex hypertonia spasticity pathological reflexes (+ babinski)
lower motor lesion characteristics
individual muscles may be affected mild weakness marked muscle atrophy fasciculations decreased muscle stretch reflex hypotonia flaccidity (-) babinski sign
Types of lower motor neuron BULBAR diseases
bulbar palsies, amyotrophic lateral sclerosis (ALS- this is mixed upper and lower)
types of lower motor neuron Anterior Horn Cell diseases
poliomyelitis, motor system disease, polyneuritis, amyotrophic lateral sclerosis
types of lower motor neuron primary muscle diseases
muscular dystrophies, myasthenia gravis, polymyositis
causes of upper motor neuron motor cortex diseases
cerebral palsy, neoplasms, trauma, inflammations, ALS
causes of upper motor neuron internal capsule diseases
vascular lesions (CVA, thrombosis, embolism, hemorrhage, aneurysm), neoplasm, trauma inflammations
causes of upper motor neuron brainstem diseases
demyelinating diseases (MS), vascular lesions, neoplasms, trauma, inflammations, degenerative disease (Parkinson’s), ALS
causes of upper motor neuron spinal cord diseases
demyelinating diseases, neoplasms, trauma, inflammations, ALS
which upper motor neuron diseases are we focusing on for exam purposes
cerebral palsy, MS, CVA, Parkinson’s, Huntington’s
Cerebral Palsy is a ____ disorder
non-progressive
cerebral palsy is caused by
injury or abnormal development in the immature brain, before, during, or after birth up to 1 year of age
cerebral palsy is from damage to or defect of
the corticospinal pathway
Signs and symptoms of cerebral palsy
muscle weakness, loss of fine motor control, impaired speech, drooling, exaggerated deep tendon reflexes, spasticity, rigidity of extremities, scoliosis, contractures, joint dislocation
Associated problems with cerebral palsy
vision and hearing impairment, swallowing problems, seizures, intellectual disability, reflux disease, abnormal touch/pain perception, osteopenia
in patients with cerebral palsy symptoms
don’t worsen but become more apparent
cerebral palsy treatment
no cure
Botulinum toxin - prevent release of ACh decreasing spasticity
PT/OT
Surgery - ortho, dental, general, ophthalmology, ENT
(dorsal rhizotomy, antireflux operation, intrathecal baclofen pump)
What does a dorsal rhizotomy treat
treats muscle spasticity, cuts the nerve at the root
anesthetic considerations for cerebral palsy
hold preop sedatives and cautious with opioids, difficult vascular access, difficult airway, decrease MAC need, slow emergence, cautious administration of NDMR
cerebral palsy patients are prone to ____ perioperatively
bleeding, hypothermia, intravascular depletion
what is the main concern (organ system) for cerebral palsy patients?
respiratory
Multiple sclerosis is an ____ disease characterized by ___
autoimmune disease characterized by combo of demyelination, inflammation, and axonal damage of the CNS
which kind of nerves are not affected with MS?
peripheral nerves are not affected
Signs and symptoms of MS
parathesia, muscle fatigue and weakness, painful muscle spasm, visual problems (optic neuritis, diplopia), autonomic instability, bulbar muscle dysfunction, cognitive dysfunction
treatment of MS is directed at and includes
decrease spasticity, tremors, bladder spasticity
- diazepam, dantrolene, baclofen
- glucocorticoids and immunosuppressants
- CD20 monoclonal antibody, interferon B1a or glatiramer acetate
situations that exacerbate the symptoms of MS
stress, increased body temperature, infection, hyponatremia
anesthetic considerations of MS
avoid succinylcholine, scopolamine, and atropine use NDMR cautiously don't have surgery during flare avoid spinal block aspiration risk increase risk of DVT stress dose steroids exaggerated hypotensive effects
CVA is characterized by
sudden neurologic deficits resulting from ischemia or hemorrhage
CVA of the anterior cerebral artery causes
contralateral leg weakness
CVA of the middle cerebral artery causes
contralateral hemiparesis and hemisensory deficit (face and arms), aphasia, contralateral visual field defect
CVA of the posterior cerebral artery causes
contralateral visual field defect and hemiparesis
CVA of the penetrating arteries causes
contralateral hemiparesis, contralateral hemisensory deficits
CVA of the basilar artery causes
oculomotor deficits and/or ataxia, crossed sensory and motor deficits
CVA of the vertebral artery causes
lower cranial nerve deficits and/or ataxia with crossed sensory deficits
CVA is the ___ leading cause of death
4th
Signs and symptoms of CVA
HA, confusion, aphasia, decreased cough/swallow reflex, hemiparesis or hemiplagia, incontinence, seizures, hyperthermia, emotional lability, horner’s syndrome, vomiting, perceptual defects, HTN, apraxia
TIA signs and symptoms
HA, confusion, vertigo, dysarthria, transient hemiparesis, temporary vision changes, syncope
What is the first thing that ERs typically do when stroke is suspected
CT scan to determine if ischemic or hemorrhagic
treatment of CVA
ASA, TPA (IV or direct infusion), surgery (crani, cerebellar resection)
anesthetic considerations for CVAs
aspiration risk, DVT risk, BS maintenance, BP maintenance
What do we want to avoid in CVA patients
hyperglycemia, dehydration, hyperthermia, infection
What would be a good anesthetic option for CVA patients
regional with MAC
Parkinson’s disease is a ___ disorder
neurodegenerative disorder of unknown cause
Parkinson’s disease has a characteristic loss of
dopaminergic fibers in the basal ganglia, regional dopamine is also depleted
depletion of dopamine results in
diminished inhibition of neurons controlling the extrapyramidal motor system and unopposed stimulation by Acetylcholine
signs and symptoms of Parkinson’s disease
skeletal muscle tremor (pill rolling) at rest, rigidity, atkinesia, diaphragmatic spasms, dementia, depression, facial immobility (infrequent blinking, paucity of emotional expressions), shuffled gait
triad of Parkinson’s disease
tremors
akinesia
rigidity
treatment for Parkinson’s disease
levodopa, carbidopa, amantadine, selegiline, rasagiline, surgery (DBS - deep brain stimulation)
What do we worry about with Selegiline therapy
risk of serotonin syndrome
Which volatile anesthetic can exacerbate Parkinson’s disease
isoflurane
Carbidopa is a
peripheral dopa decarboxylase inhibitor
Amantadine is an ___ and can cause ___
antiviral; prolonged QT
If a patient is taking Rasagiline what do we need to check/monitor?
blood sugars
anesthetic considerations for parkinson’s disease
continue levodopa therapy, will see HoTN and cardiac dysrhythmias at induction, use Sevoflurane, avoid benzos, use direct acting agents such as phenylephrine, risk of periop HTN, aspiration, laryngospasm
What is less effective is someone is on anticholinergics in Parkinson’s
NDMR
Huntington’s disease is a ___ characterized by ___
degenerative disease of the CNS characterized by marked atrophy of the caudate nucleus, putamen, and globus pallidus
signs and symptoms of Huntington’s disease
progressive dementia, chorea, tremors, rigidity/contractures, depression, aggressive outburt, mood swings, difficulty with speech and swallowing, weight loss
treatment of Huntington’s disease
treat choreiform movements, Haldol, antidepressants, PT/OT/speech therapy
anesthetic considerations for Huntington’s disease
aspiration risk, prolong response to succinylcholine, sensitive to NDMR, consider avoiding reglan and anticholinergics, use glycopyrrolate > atropine
lower motor neuron diseases we are going to focus on for the purposes of the exam
MG, MD, Lambert-Eaton, myotonic dystrophy, mitochondrial disorder, Guillain Barre, spinal muscular atrophy
myasthenia gravis is
autoimmune destruction or inactivation of postsynaptic acetylcholine receptors at the neuromuscular junction leading to reduce numbers of receptors and degradation of their function
signs and symptoms of myasthenia gravis
diplopia, ptosis, fluctuating fatigue and weakness that improves after rest, muscle weakness of mouth and throat, dyspnea with exertion, proximal muscle weakness
treatment of myasthenia gravis
cholinesterase inhibitor, plasmapheresis, corticosteroids, immunosuppressants, immunoglobins, thymectomy
situations that exacerbate myasthenia gravis
pregnancy, infection, electrolyte imbalance, surgical and psychological stress, aminoglycoside antibiotics
pregnancy and myasthenia gravis
increased weakness in 3rd trimester
baby may show S/S of MG requiring intubation when they are born
anesthetic considerations for myasthenia gravis
aspiration risk, sensitive to NDMR, sensitive to respiratory depressants, regional preferred (amides not esters), resistant to succinylcholine
lambert-eaton is 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 acetylcholine at the motor end plate
signs and symptoms of lambert-eaton
proximal muscles are mostly affected, weakness generally worse in the morning and improves thru the day, respiratory and diaphragm muscles become weak, autonomic nervous system dysfunction (orthostatic HoTN, slowed gastric motility, urinary retention), dry mouth, impotence, small cell carcinoma
treatment for lambert-eaton
3,4-DAP, guanidine hydrochloride, corticosteroids, immunosuppressants, plasmapheresis
anesthetic considerations for lambert- eaton
sensitive to succinylcholine and NDMR, inadequate reversal with anticholinesterase, high risk of postop respiratory failure
60% of patients with lambert- eaton have
small cell carcinoma
duchenne muscular dystrophy is a ___ disorder that results from __
X linked recessive disorder that results from production of abnormal protein dystrophin
duchenne muscular dystrophy affects ___>___ and presents between ____ years of age
males > females, 3-5 years of age and don’t live past 30 years old usually
signs and symptoms of duchenne MD
symmetric proximal muscle weakness “gower sign”, fatty infiltration causes enlargement of muscles (calves), kyphoscoliosis, respiratory muscle weakness, degeneration of cardiac muscles, impaired GI hypomotility, imparied airway reflex, impaired cardiac conduction, cognitive impairment, pulmonary hypertension
becker muscular dystrophy is a ____ disorder
X linked recessive disorder (just less common)
signs and symptoms of becker muscular dystrophy
presents later in life (adolescence), progress slower, intellectual disability less common, proximal muscle weakness, prominent calf pseudohypertrophy, degeneration of cardiac muscles
what do patients with becker muscular dystrophy die from?
respiratory complications
diagnosis of muscular dystrophy
genetic testing, CK levels (usually 10x higher), muscle biopsy (rare)
treatment for muscular dystrophy
surgery (for scoliosis, release contractures, ex lap for ileus), PT, steroids, biphosphates, mystatin inhibitors, gene modification, protease inhibitors, stem cell infusions
why are steroids a good treatment in muscular dystrophy
delay progression of disease by 2-3 years
anesthetic considerations for muscular dystrophy
risk of MH like syndrome (rhabdomyolysis, hyperkalemia), avoid succinylcholine and volatiles, avoid opioid and benzos preop, intraop position complications d/t kyphoscoliosis, sensitive to NDMR, local and regional preferable, aspiration risk, look at echo, ecg, PFTs
myotonic dystrophy is a ___ disease
hereditary degenerative disease of the skeletal muscle that results in the dysfunctional calcium sequestration by the SR
sodium and chloride channel dysfunction
signs and symptoms of myotonic dystrophy
weakness, inability to relax hand grip (myotonia), cardiomyopathy, conduction defects (1st degree), dysphagia, slowed gastric emptying, endocrine dysfunction, central sleep apnea, ptosis
triad in males with myotonic dystrophy
frontal balding, cataracts, testicular atrophy
treatment for myotonic dystrophy
procainamide, phenytoin, mexiletine, baclofen, dantrolene, carbamazepine, cardiac pacemaker
anesthetic considerations for myotonic dystrophy
avoid succ, aspiration risk, volatile anesthetics may produce exaggerated myocardial depression, neostigmine and physostigmine can aggravate myotonia, sensitive to respiratory depressants, maintain normothermia and avoid shivering, have PFTs, ecg, and transthoracic pacing available
mitochondrial disorders are a group of disorders of __
skeletal muscle energy metabolism
mitochondria produce the energy required by skeletal muscle cells through
oxidation-reduction reactions of the electron transfer chain and oxidative phosphorylation (generating ADP)
signs and symptoms of mitochondrial disorders
abnormal fatigability with sustained exercise
skeletal muscle pain and progressive weakness
hearing loss, impaired vision
balance and coordination problems
seizures
learning deficits
treatment for mitochondrial disorders
treat symptoms, administer metabolites and cofactors, sodium bicarbonate/dichloroacetate, ketogenic diet
anesthetic considerations for mitochondrial disorders
prone to acidosis and dehydration, lactate level, avoid propofol for continuous infusion, avoid succinylcholine and LR, maintain normothermia, use caution with NDMR and local anesthetics, avoid prolonged tourniquets, avoid bupivacaine
Guillain Barre is an
immunologic assault on myelin in the peripheral nerves particularly lower motor neurons, the action potential cannot be conducted so the motor endplate doesn’t receive the incoming signal
guillain barre typically persists for ___ and ends ___
2 weeks; with full recovery in 4 weeks with some permanent paralysis remaining
signs and symptoms of guillain barre include
flaccid paralysis that begins in the distal extremities and ascends bilaterally, intercostal muscle weakness, facial and pharyngeal weakness, sensory deficits, autonomic dysfunction, paresthesia, vital sign changes
treatment for guillain barre
plasmapheresis, IVIG if plasmapheresis CI
what is not useful in treatment of guillain barre
steroids
when is plasmapheresis contraindicated?
in hemodynamically unstable patients or if they are bleeding
anesthetic considerations for guillain barre
avoid succinylcholine, sensitive to NDMR, increased risk of DVT, risk of aspiration, exaggerated response to indirect sympathomimetics, high incidence of SIADH (monitor Na+), controversy of combined GA and regional, controversy with epidural, slow position changes, avoid respiratory depressants, risk of postop mechanical ventilation
spinal muscular atrophy are due to
deletions or mutations in the survival motor neuron gene on chromosome 5q13
the 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 and affect the anterior horn of the spinal cord
SMA I is also known as
infantile spinal muscular atrophy
SMA I is an autosomal recessive disorder that manifests
usually within the first 3 months of life
infants with SMA I have difficulty
swallowing, sucking, and breathing
SMA I is ____ progressive leading to ___
rapidly; death from respiratory complications usually by age 3
SMA II begins
latter half of the first year of life
SMA II has ___ progression vs SMA I
slower
SMA III develops at what age
after age 2
SMA III develops weakness of ____
proximal limb muscles with relative sparing of bulbar muscles
treatment of SMA
spinraza, zolgensma, evrysdi, PT, surgery, antibiotics
anesthetic considerations for SMA
pulmonary consultation, difficult intubation, avoid succ, varying sensitivity to NDMR, regional is controversial, cautious with opioids, postop mechanical ventilation likely
what is an example of a mixed motor neuron disease
amyotrophic lateral sclerosis (ALS)
ALS is a
rapidly progressive degeneration of motor neurons in the corticospinal tract (primary descending upper motor neurons) and the lower motor neurons in the anterior horn gray matter of the spinal cord
what replaces the affected motor neurons in ALS?
astrocytic gliosis
signs and symptoms of ALS
spasticity, hyperreflexia, loss of coordination, muscle weakness, fasciculations, atrophy in hands, orthostatic HoTN, resting tachycardia, sensation remains intact
what typically remains intact in ALS?
bladder and bowel function
treatment for ALS
riluzole (NMDA receptor antagonist), edaravone, spasmolytics, analgesics
what is the only drug that reduces mortality in ALS
riluzole
anesthetic considerations for ALS
avoid succ, increase sensitivity to NDMR, aspiration risk, consider postop mechanical ventilation, increase sensitivity to respiratory depressants, autonomic dysfunction with hemodynamic instability risk, avoid spinal anesthesia
What heart rhythm can ALS patients go into after induction?
PEA
A patient with myasthenia gravis will be sensitive to ____ and resistant to ____
rocuronium; succinylcholine
characteristics of lower motor neuron lesion
fasciculations, flaccidity
