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Neuromuscular Disorders. Ping-Wei Chen PGY – 2 Emergency Medicine Resident April 8, 2010 Thanks: Dr. Walker, Dr. Burton-MacLeod, Dr. Oster , Dr. Brownell. Weakness. Non-Neuromuscular Cardiovascular Respiratory Infectious Metabolic Endocrine Toxicologic. Neuromuscular Brain

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neuromuscular disorders

Neuromuscular Disorders

Ping-Wei Chen

PGY – 2

Emergency Medicine Resident

April 8, 2010

Thanks: Dr. Walker, Dr. Burton-MacLeod, Dr. Oster, Dr. Brownell

weakness
Weakness
  • Non-Neuromuscular
    • Cardiovascular
    • Respiratory
    • Infectious
    • Metabolic
    • Endocrine
    • Toxicologic
  • Neuromuscular
    • Brain
    • Spinal Cord
    • Anterior Horn Cell
    • Peripheral Nerve
    • Neuromuscular Junction
    • Muscle
localizing the lesion umn vs lmn
Localizing the Lesion: UMN vs LMN
  • Upper motor neuron
    • Unilateral symptoms
    • If bilateral symptoms, associated
      • Altered mental status
      • Cranial nerve abnormalities
    • If bilateral symptoms and normal mental status
      • THINK spinal cord
myelopathy
Myelopathy
  • Pathology of the spinal cord
  • Clinically:
    • UMN signs
    • Ascending weakness
    • Bowel/Bladder involvement
    • Sensory involvement (define level)
anterior horn cell
Anterior Horn Cell
  • UMN synapses with LMN here
  • Clinically:
    • Both UMN/LMN signs
    • Little/No sensory involvement
    • Bulbar symptoms (ALS)
      • Speech
      • Swallowing
      • Chewing
neuropathy
Neuropathy
  • Peripheral nerve pathology
  • Clinically:
    • LMN signs
    • Distal to proximal involvement
      • “glove and stocking” pattern
    • Varied sensory involvement
neuromuscular junction
Neuromuscular Junction
  • Connection between CNS and muscles
  • Clinically:
    • Variable presentations of weakness
      • Fatigability
      • Proximal
      • Ascending vs Descending
    • No sensory involvement
myopathy
Myopathy
  • Muscle pathology
  • Clinically:
    • LMN signs
    • Proximal > Distal
    • ±muscle tenderness
slide10
Case
  • 65M with weakness.
    • 2x visits to GP in last 3 months for same.
    • Notices:
      • sometimes chokes on food
      • Blurry vision when tired
      • Generalized fatigue
    • “Enough is enough”
  • O/E:
    • Normal PERL
    • Rapid neurological exam otherwise normal.
  • Any thoughts?
myasthenia gravis
Myasthenia Gravis
  • RARE
  • Rarely diagnosed in ED
  • Bi-modal age of onset
    • Women 20-40
    • Men 50-70
myasthenia gravis1
Myasthenia Gravis
  • Autoantibodies against Nicotinic ACh receptors
    • Decreased number of post-synaptic ACh receptors
    • Compete for binding on ACh receptors with ACh
myasthenia gravis2
Myasthenia Gravis
  • Clinically:
    • Fatigability of voluntary muscles
      • BEWARE – respiratory muscles
    • Ocular symptoms first
      • Ptosis, diplopia, blurred vision
    • Normal sensation
    • No pain
myasthenia gravis3
Myasthenia Gravis
  • Diagnosis
    • Clinical + Further Testing
      • Edrophonium/Ice Bag Test
      • Anti-ACh Receptor Antibody
      • Muscle Specific Receptor Tyrosine Kinase Antibody
      • Electrophysiologic Tests
myasthenic crisis
Myasthenic Crisis
  • MG + Respiratory failure requiring intubation
    • 15%-20% MG patients
  • Precipitants
    • Infection (most common)
    • Medication changes
    • Surgery
    • Pregnancy/Childbirth
    • Unidentified (30%)
back to our patient
Back to our patient
  • When to intubate?
  • Caution:Don’t rely on work of breathing!
  • Spirometry
    • FVC ≤ 1L = intubate
    • Rate of decrease in FVC
    • “sooner rather than later”
cholinergic crisis
Cholinergic Crisis
  • Excessive anticholinesterase medication
    • Too much Acetylcholine

Acetylcholine

Succinylcholine

myasthenic vs cholinergic crisis
Myasthenic VS Cholinergic Crisis
  • May be difficult to differentiate
    • Response to Edrophonium/Ice Bag Test
    • Presence of muscarinic symptoms
  • Cholinergic crisis rare unless >> dose ingested
    • ie: pyridostigmine >120mg every 3 hours
  • Assume weakness 2o worsening MG
edrophonium tensilon test
Edrophonium/Tensilon Test
  • Edrophonium
    • 135mg IV
    • Response 30-90s?
    • Adverse effect?
  • Max dose 10mg IV
  • Caution
    • Asthmatics/COPD
  • Atropine at bedside!!
  • Measure distance between upper and lower eyelid in most affected eye
ice bag test
Ice Bag Test
  • Apply ice to most affected eye X 2 mins
  • Measure distance between upper and lower eyelid in most affected eye
myasthenia gravis4
Myasthenia Gravis
  • Management
    • Emergency Department
      • Identify
      • Supportive
        • Early intubation for respiratory failure
    • Neurology/ICU
      • Anti-cholinesterase Medications
        • Pyridostigmine
      • Immunomodulation
        • Plasmapheresis, IVIG
        • Glucocorticoids, Azathioprine, MycophenolateMofetil, Cyclosporine
      • Thymectomy
clinical pearls
Clinical Pearls
  • Do spirometry!
    • Insidious respiratory failure
    • FVC ≤1L = ICU consult, FVC≤500cc
  • Sick Myasthenia Gravis patient?
    • *Continue acetylcholinesterase inhibitor meds*
  • Admitting Myasthenia Gravis patient?
    • Neurology consult
slide24
Case
  • 62M with known small cell lung Ca
    • Generalized leg weakness
    • Difficulty climbing stairs
  • Could this be Lambert-Eaton Syndrome?
lambert eaton syndrome
Lambert-Eaton Syndrome
  • RARE
  • Strong association with neoplasm (SCLC)
  • Auto-antibodies to Voltage Gated Ca channels
    • Decreased release of ACh from pre-synaptic terminal
lambert eaton syndrome1
Lambert-Eaton Syndrome
  • Clinically:
    • Proximal muscle weakness (
    • Autonomic dysfunction (anti-cholinergic)
    • Variable bulbar involvement
  • Differentiation from MG
    • Weakness improves with use of muscle
    • Autonomic involvement
slide27
Case
  • 41yo male with nausea and diarrhea X 24 hrs
  • “really weak”
    • Difficulty holding head up for long periods
    • Arms weak
  • Blurred vision, dry mouth
  • ? “food poisoning”
    • moloha
  • Any thoughts?
botulism
Botulism
  • Clostridium botulinum
    • Obligate anaerobe
    • Spore forming
    • Toxin producing
  • Mechanism of Action
    • Irreversible binding to presynaptic membrane of peripheral and cranial nerves
      • inhibiting ACh release
    • Disperses widely via vascular system regardless of portal of entry
botulism1
Botulism
  • Clinical Entities
    • Food-borne
    • Infantile
    • Wound
    • Adult Enteric Infectious Botulism/Adult Infectious Botulism of Unknown Source
    • Inhalational
botulism2
Botulism
  • Clinically:
    • Both voluntary and autonomic involvement
    • Symptom onset 6-48hrs post-ingestion of toxin
      • Descending, symmetrical paralysis
      • ±GI tract symptoms (N/V/D, abdo cramps, constipation)
      • ±Anti-cholinergic symptoms
        • Pupils dilated and non-reactive to light*
      • No sensory involvement
      • No pain
      • No fever

*differentiates from myasthenia gravis

infantile botulism
Infantile Botulism
  • Clinically:
    • Constipation
    • Weak Cry
    • Feeding difficulties/Anorexia
    • Descending/Global Hypotonia
    • Lethargy
botulism3
Botulism
  • Diagnosis
    • Clinical Diagnosis (exclude other pathology)
      • Home canned foods, contaminated aquatic products, honey (infants)
      • Vegetables
    • Centre for Disease Control and Prevention 1998
      • Suspect in
      • Adult with acute onset dysfunction of
        • GI tract
        • Autonomic nervous system (anticholinergic symptoms)
        • Cranial nerve dysfunction
      • Infant with acute onset of
        • Poor feeding
        • Diminished crying ability
        • Weakness
        • Respiratory distress
botulism4
Botulism
  • Diagnosis
    • Laboratory tests rarely helpful in initial management
      • Toxin/Spore Analysis
        • Serum, Stool, Vomitus, Food
      • Wound Cultures
management
Management
  • Supportive Care
    • Early intubation for respiratory failure
    • Equine Trivalent Anti-toxin
      • >1 year old
      • Decrease mortality, disease duration (if given early)
      • Unclear effect on ventilator dependence
      • Side effects: serum sickness, anaphylaxis
    • Human Botulism Immune Globulin (BIG-IV)
      • <1 year old
    • Antibiotics in Wound Botulism
      • Penicillin G or Metronidazole (allergy)
slide35
Case
  • 9yo male
  • 1 day history of:
    • Tripping when walking
    • Legs “feeling tight”
  • Seen by GP earlier; clinic note faxed
    • Neuro exam abnormalities
      • 4+/5 strength bilaterally in lower extremities
      • Sensation grossly normal
      • Able to ambulate but “clumsy”
      • Bloodwork normal
    • Go to ED if gets worse
slide36
Case
  • Now back: can’t walk or sit up independently
  • “A cold” 3 weeks ago
  • Otherwise healthy, IUTD
  • O/E:
    • Normal cranial nerves
    • No sensory level
    • Decreased DTRs
slide38
Case
  • Bloodwork unremarkable
    • Electrolytes normal
    • No increased WBC
  • Other investigations?
  • Any thoughts?
guillain barre syndrome
Guillain-Barre Syndrome
  • Most common cause of acute symmetrical weakness in developed countries
  • 1-2 per 100,000 worldwide
  • All ages affected
    • Peaks in young adults and elderly
guillain barre syndrome1
Guillain-Barre Syndrome
  • Heterogeneous syndrome with several variant forms
    • Acute Inflammatory DemyelinatingPolyneuropathy
    • Miller-Fisher Syndrome
    • Acute Motor Axonal Neuropathy
    • Acute Sensorimotor Axonal Neuropathy
  • Autoimmune response to preceeding infection
    • Molecular mimicry
    • Campylobacter
    • HIV, EBV, CMV, H. influenza, E. coli
guillain barre syndrome2
Guillain-Barre Syndrome
  • Clinically:
    • Progressive, relatively symmetric muscle weakness
      • Usually ascending, then generalized
    • Distal paresthesias
    • Decreased/Absent deep tendon reflexes
    • Dysautonomia
    • Variable involvement
      • Facial muscles
      • Bulbar muscles
      • Cranial Nerves
  • Investigations:
    • Increased protein in CSF; normal white cell count
guillain barre syndrome3
Guillain-Barre Syndrome
  • Management
    • Emergency Department
      • Supportive
        • Early intubation for respiratory failure (15-30%)
        • Hemodynamic monitoring (autonomic dysfunction)
    • Neurology/ICU
      • Plasmapheresis
      • IVIG
      • No role for steroids
tick paralysis
Tick Paralysis
  • Summer months
  • Tick Endemic Areas
    • Pacific Northwest (BC)
    • Rocky Mountains
  • Injection of ixovotoxin with tick feeding
    • Diminish release of ACh
    • Slow nerve conduction velocity
  • Clinically:
    • Early: restless, irritable, hand/feet paresthesia
    • 24-48hrs:
      • ascending, symmetrical, flaccid paralysis
      • ±cerebellar dysfunction
tick paralysis1
Tick Paralysis
  • Diagnosis:
    • Clinical; no diagnostic laboratory measure
  • Management:
    • Supportive Care
      • Early intubation for respiratory failure
    • Tick Removal
slide45
Case
  • 46yo woman with ALS
    • 5 days of productive cough (clear, now green)
    • Fever 38.9oC today
    • No GI/GU symptoms
  • O/E:
    • HNT – normal
    • CV – tachycardic (115bpm)
    • Resp – RR46, SCM use, crackles R lung field
    • Abdo – soft, nontender, no CVA tenderness
    • MSK – no rashes
amyotrophic lateral sclerosis
Amyotrophic Lateral Sclerosis
  • 1-3 per 100,000
  • Sporadic and Familial forms
  • Increasing incidence after 40yo; peaks 70-80yo
  • Clinically:
    • Progressive UMN/LMN symptoms (months/years)
    • Asymmetric weakness (distal to proximal)
    • No sensory findings
amyotrophic lateral sclerosis1
Amyotrophic Lateral Sclerosis
  • Management
    • Supportive Care
    • Advanced Directive?
      • Moss et al. Chest. 1996
        • Case Series (n=75)
          • 72% ALS patients aware of disease progression to respiratory failure
          • 48% ALS patients learned this from MD
          • 42% ALS patients made decision re: long term ventilation prior to crisis
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