Neuromuscular disorders
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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


Localizing the lesion umn vs lmn1

Localizing the Lesion: UMN vs LMN


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


Neuromuscular disorders

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


Neuromuscular junction1

Neuromuscular Junction


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


Neuromuscular disorders

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 (<MG) ± soreness

    • Autonomic dysfunction (anti-cholinergic)

    • Variable bulbar involvement

  • Differentiation from MG

    • Weakness improves with use of muscle

    • Autonomic involvement


Neuromuscular disorders

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)


Neuromuscular disorders

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


Neuromuscular disorders

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


Video exam

Video Exam


Neuromuscular disorders

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


Neuromuscular disorders

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


Intubate

Intubate?


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


Questions

Questions?


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