Neuromuscular Flashcards
Upper Motor Neurons
Cerebral cortex → ventral motor horn
Direct, influence, & modify reflex arcs
Form synapses w/ interneurons & lower motor neurons before projecting to periphery
Corticospinal Tract
Motor transmission
Receives information from sensory cortex
AP to 1° motor neuron
Synapses w/ 2° efferent motor neuron
Decussates at medulla & travels down the spinal cord via the anterolateral tract
2° motor nerve synapses w/ 3° efferent motor neuron at ventral horn
3° (lower motor neuron) projects down to the skeletal muscle
Corticobulbar Tract
Cranial nerves
Bilaterally III, IV, VI, IX, X, XI
Unilateral facial VII & hypoglossal XII
Involved in precise motor movements
Lower Motor Neurons
Neurons located in brain stem & spinal cord
Direct influence on muscles
Send axons into PNS to synapse one & control skeletal muscle cells
Lower motor neurons that pass through the spinal nerves 1° control limb & trunk muscles
Pass through cranial nerves 1° control the head & neck skeletal muscles
NMJ
Neuromuscular junction
AP initiates synaptic transmission
Na+ channels depolarize the axon terminal membrane
Depolarization causes VGCa2+ channels to open
ACh diffuses across the synaptic cleft & binds to receptors on postsynaptic membrane
Depolarizes post-synaptic AP
ACh uptake to resynthesize/recycle
Upper Motor Lesions
Motor cortex Muscle groups are affected Mild weakness Minimal diffuse muscle atrophy No fasciculations ↑muscle stretch reflex Hypertonia & spasticity Pathological reflexes
Lower Motor Lesions
Ventral horn (spinal cord) & motor nuclei (brainstem) Individual muscles affected Mild weakness Severe muscle atrophy Fasciculations ↓muscle stretch reflex Hypotonia & flaccidity - Babinski sign
Upper Motor Neuron Disorders
Cerebral palsy Multiple sclerosis CVA Parkinson's Huntington's
Cerebral Palsy
Non-progressive disorder caused by injury or abnormal development in the immature brain
Before, during, or after birth up to 1yo
Damage or defects in the corticospinal pathway
CP S/S
Muscle weakness Loss fine motor control Impaired speech Drooling Exaggerated deep tendon reflexes Spasticity Extremity rigidity Scoliosis, contractures, joint dislocation
Vision or hearing impairment Swallowing problems Seizures Intellectual disability Reflux disease
CP Treatment
No cure ↑ADLs Surgery (ortho, dental, general, ophthalmology, ENT) - Dorsal rhizotomy - Antireflux operation - Intrathecal baclofen pump Botulinum toxin PT/OT
CP Anesthetic Considerations
Hold preop sedative Caution w/ opioids Difficult vascular access Airway concerns d/t dentition, secretions, TMJ, ankylosis, & contractures Potential RSI Succinylcholine does not ↑K+ release Cautious NDMR admin ↓MAC 20-30% Prone to bleeding, hypothermia, & intravascular depletion Slow emergence
Multiple Sclerosis
Autoimmune disease characterized by combination demyelination, inflammation, & CNS axonal damage
Peripheral nerves not affected
MS S/S
Parethesias (face, arms, fingers, legs) Muscle weakness/fatigue Painful muscle spasms Visual problems (optic neuritis & diplopia) Autonomic instability Bulbar muscle dysfunction Cognitive dysfunction (advanced MS)
MS Treatment
↓spasticity, tremors, bladder spasms Diazepam Dantrolene Baclofen Glucocorticoids Immunosuppressants CD20 monoclonal antibody - interferon B1a of glatiramer acetate
S/S exacerbated by stress, ↑body temp, infection, hyponatremia
MS Anesthetic Considerations
AVOID SUCCINYLCHOLINE Caution w/ NDMR admin Avoid surgery during flare Avoid spinal block Epidurals safe Aspiration risk ↑risk DVT Stress-dose steroids Exaggerated hypotensive effects
Cerebrovascular Accident
Stroke characterized by sudden neurologic deficits resulting from ischemia 88% or hemorrhage 12%
CVA S/S
Anterior cerebral artery - contralateral leg weakness
Middle cerebral artery - contralateral hemiparesis & sensory deficit (face/arms > legs), aphasia, contralateral visual field defect
Posterior cerebral artery - contralateral visual field defect & hemiparesis
Penetrating arteries - contralateral hemiparesis & contralateral hemisensory deficits
Basilar artery - oculomotor deficits and/or ataxia & crossed sensory & motor deficits
Vertebral artery - lower cranial nerve deficits & ataxia w/ crossed sensory deficits
CVA Treatment
Aspirin
TXA (IV admin or VIR direct infusion)
Surgery (crani/cerebellar resection)
CVA Anesthetic Considerations
Aspiration & DVT risk
Maintain blood glucose
Blood pressure maintenance
Parkinson’s Disease
Neurodegenerative disorder
Unknown cause
Loss dopaminergic fibers in the basal ganglia
Regional dopamine concentrations are also depleted
Results in diminished neuron inhibition controlling the extrapyramidal motor system & unopposed ACh stimulation
Parkinson’s S/S
Skeletal muscle rigidity (pill-rolling) - more prominent during rest & disappears during voluntary movement
Rigidity
Akinesia - loss voluntary movement
Diaphragmatic spasms
Dementia
Depression
Facial immobility (infrequent blinking & paucity emotional expressions)
Parkinson’s Treatment
Levidopa - dopamine precursor Carbidopa - peripheral dopa decarboxylase inhibitor Amantadine Selegline & Rasgiline Rpinirole - dopamine agonist Entacapone - COMT inhibitor Donepezil & Taurine - AChEi Amatadine - antiviral
Parkinson’s Anesthetic Considerations
Continue Levidopa therapy Aspiration/airway risk Hypertension Post-extubation laryngospasm Avoid benzodiazepines Ideal volatile agent = Sevoflurane NDMB less effective Use Sugammadex Avoid indirect-acting NT releaser (Ephedrine) Hypotension & cardiac dysrrhythmias
Huntington’s Disease
DNS degenerative disease characterized by marked caudate nucleus atrophy & putamen & globus pallidus to lesser degree
Autosomal dominant
Huntington’s S/S
Progressive dementia
Chorea (involuntary jerking or writhing movement)
Tremors
Rigidity & contractures
Depression, aggressive outburst, mood swings
Difficulty w/ speech & swallowing
