Neuromuscular Emergencies - PowerPoint PPT Presentation

Loading...

PPT – Neuromuscular Emergencies PowerPoint presentation | free to download - id: 3d7249-ZjQyM



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Neuromuscular Emergencies

Description:

NEUROMUSCULAR EMERGENCIES July 28, 2010 Sandra Derghazarian Management General Stop any meds that may be contributing Treat any infection Specific PLEX and IVIG ... – PowerPoint PPT presentation

Number of Views:81
Avg rating:3.0/5.0
Slides: 56
Provided by: neurology
Learn more at: http://neurology.mcgill.ca
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Neuromuscular Emergencies


1
Neuromuscular Emergencies
  • July 28, 2010
  • Sandra Derghazarian

2
Outline
  • Approach to rapidly progressing LMN weakness
  • Myasthenic crisis
  • GBS

3
Intro
  • Three major tasks
  • Assess stability, signs of imminent resp failure
  • Generate differential diagnosis
  • Knowledge of localisation
  • Knowledge of major disorders
  • Determine management

4
Brief Review of Anatomy
  • Motor unit anatomy
  • Anterior horn cell
  • Its motor axon
  • The synaptic cleft
  • The muscle fibers it innervates
  • Remember sensory and autonomic systems
  • Many disorder with rapidly progressing peripheral
    neuropathic weakness will have sensory loss and
    dysautonomia

5
Classification
  • Motor neuron
  • Loss of anterior horn cells
  • Motor axon
  • Disruption of myelin sheath
  • Axonal degeneration
  • Neuromuscular junction
  • Pre-synaptic (e.g. Release of Ach)
  • Post-synaptic (e.g. Abnormalities of Ach
    receptor)
  • Muscle
  • Membrane, contractile elements
  • Genetic or acquired secondary (infex, inflamm,
    vasc.)

6
Approach to Determining Cause of Weakness
  • Knowledge of some of the possible disorders
  • Focused history
  • Physical exam
  • Lab studies

7
Major Disorders
8
History Key Elements
  • Pre-existing NM disorder?
  • MG exacerbation 2ary systemic illness,
    medication
  • ALS accelerated phase, decompensation 2ary
    pneumonia
  • Pre-existing systemic disorder?
  • Malignancy, CTD, sepsis
  • What drugs is pt taking?
  • Any recent illness?
  • Diet in last 48 hours?
  • Shellfish (saxitoxin, brevetoxin)
  • Home-canned goods (botulinum toxin)
  • Any possible exposure to tick bite, snake bite?
  • Any sensory or autonomic symptoms?

9
Drugs
  • Diuretics
  • Hypokalemia
  • Corticosteroids, statins, colchicine,
    cyclosporine, cocaine, chloroquine, L-tryptophan,
    penicillamine, zidovudine
  • Myotoxic effect
  • Amiodarone, cytarabine, streptokinase
  • Demyelinating neuropathy
  • Magnesium-containing antacids with pre-existing
    renal insufficiency
  • Hypermagnesemia

10
Physical Exam
  • Vital signs
  • Unstable?
  • Dysautonomia?
  • Respiratory status

11
Signs of impending NM resp failure
  • Tachypnea, sinus tachycardia
  • Staccato speech
  • Inability to count to 20
  • Profound weakness of neck flexion
  • Use of accessory muscles (visible, palpable)
  • Orthopnea
  • Paradoxical breathing pattern
  • Signs of bulbar dysfunction (nasal voice,
    accumulation of saliva, weak cough)
  • ? think about aspiration!

12
Physical Exam
13
Physical Exam
  • Vital signs
  • Note any dysautonomia
  • Presence and pattern muscle weakness
  • Proximal (myopathy), distal (peripheral
    neuropathy)
  • Symmetric, asymmetric
  • Involvement of cranial muscles
  • Reflexes
  • Sensory changes
  • Dysautonomia

14
Localisation of the Disorders
  • Clinical picture varies depending on which part
    of motor unit is involved

15
Localisation ctnd
16
(No Transcript)
17
Regroup
  • Is respiratory failure imminent?
  • Should ICU be involved?
  • Where can I localise motor findings?
  • Does it fit with sensory findings?
  • Does it fit with autonomic findings?
  • Does it fit with the history?
  • Can the history help me narrow things down?

18
Major Disorders
19
Laboratory Studies
  • CBC
  • Anemia or leukocytosis - systemic disease
  • Eosinophilia - possibly elevated in vasculitic
    neuropathy, porphyria
  • Lytes, Cr, BUN, Ca, Mg, PO4,
  • Liver enzymes (consider EtOH myotoxicity)
  • CK (myopathy if very elevated)
  • ESR (infectious or inflammatory disorders)
  • CXR (pneumonia, atelectasis, elevated
    hemidiaphragm)
  • EKG
  • Changes associated with electrolyte imbalances
  • Arrythmias 2ary to dysautonomia in GBS
  • Axis deviation may be suggestive of
    cardiomyopathy

20
Assess Respiratory Status
  • Tests in ER
  • MIP
  • MEP
  • FVC
  • ABG
  • 20/30/40 rule
  • VC 20 ml/kg
  • MIP -30cmH20
  • MEP 40cm H20

21
Myasthenic Crisis
22
Myasthenia Gravis
  • Disorder of transmission across NM junction
  • Auto-immune and congenital form
  • Epidemiology (auto-immune form)
  • 200-400 cases per million population
  • Women gt men (32)
  • Bimodal incidence
  • F 20s, 30s M 50s, 60s
  • 5-10 co-association with other auto-immune
    disorders

23
Classification
  • Auto-immune two forms
  • Acquired anti-AChR Abs (85)
  • Acquired anti-MuSK Abs, a muscle-specific TK
  • 40-50 of anti-AChR seronegative pts
  • Congenital
  • Heterogeneous group (pre or post-synaptic)
  • Of note do not affect respiratory muscles
    therefore do not present with myasthenic crisis

24
Clinical Features
  • Painless, fatigable weakness of voluntary muscles
  • Repeated activity ? progressive paresis
  • Rest ? restoration of strength (at least partial)
  • Usually insidious onset
  • May occur more rapidly after precipitant (stress,
    infection)
  • Association with thymic abnormalities
  • 10-15 thymoma
  • 50-70 thymic lymphoid hyperplasia

25
Clinical Features
  • Presenting symptoms
  • MuSK-MG
  • Younger women
  • Predominantly facial, bulbar and respiratory
    weakness
  • Relatively mild limb weakness

26
Severity Classification
27
Myasthenic Crisis
  • Myasthenic weakness leading to respiratory
    failure and need for ventilatory assistance
  • Severe weakness of respiratory muscles
  • and/or
  • Severe weakness of upper airway muscles (bulbar
    myasthenia)

28
Prevalence and Characteristics
  • Life-time prevalence 20-30
  • Early onset ? younger pt, median onset w/in 8
    mos, fast recovery
  • Late onset ? older pts, later in dz course,
    slower recovery
  • White pts respond more poorly than black pts
  • Pregnancy aggravates MG in 30 of women
  • High potential mortality of crisis

29
Precipitants
  • Elements to look for in history/chart
  • Poor control of generalised disease
  • Medical treatment for bulbar myasthenia
  • Steroids and anti-cholinesterases
  • Use of certain drugs (next slide)
  • Systemic infection, esp. of respiratory tract
  • Aspiration
  • Surgery
  • Others (in refractory myasthenia)
  • Emotional stress
  • Hot environment
  • Hyperthyroidism

30
Drugs
  • Anticholinesterases can also lead to myasthenic
    crisis
  • Signs of excessive cholinergic activity
  • Miosis, diarrhea, salivation, abdominal cramps,
    sweating, weakness

31
Investigations
  • CBC, extended lytes, BUN, Cr, liver enzymes
  • CXR, U/A /- blood cultures
  • Obtain VC, MIP, MEP 20/30/40 rule

32
Investigations
  • Repetitive motor nerve stimulation
  • Stimulate motor nerve at 2-3 Hz and measure CMAP
    of stimulated muscle
  • Positive if gter 10 decrement in amplitude of
    CMAP from the 1st to the 5th potential
  • Positive in about 75 of patients with
    generalized MG, if
  • Proximal clinically involved muscles are tested
  • Muscle is warm
  • More than one muscle is tested
  • Single fibre EMG
  • Tensilon test not recommended in pt suspected of
    being in crisis
  • False postive, false negative
  • Risk of worsening muscle weakness in pts with
    anticholinesterase overdose
  • Worsening of bulbar and respiratory symptoms in
    MuSK-MG

33
Management
  • Monitoring of respiratory status
  • Recognition of impending resp failure
  • Tachypnea, inability to count to 20, saliva
    pooling, nasal voice, NF weakness, paradoxical
    breathing
  • Deciding when to intubate
  • (Code status)
  • 20/30/40 rule
  • If in doubt, intubate
  • ?BiPAP
  • Limited experience. May reduce prolonged intubatn
    and trach

34
Management
  • General
  • Stop any meds that may be contributing
  • Treat any infection
  • Specific
  • PLEX and IVIG comparable efficacy
  • Based on clinical evidence, few RTCs
  • Earlier response seen with PLEX
  • More likely to extubate at 14 days, better
    1-month functional outcome (Qureshi, et al.
    Neurology, 1999).

35
Management
  • PLEX
  • Removal of anti AChR and antiMuSK Abs
  • 1 session/day x 5
  • No superiority of PLEX qd x 5 vs qod x 5
  • Rapid onset of action (3-10 days)
  • Need central line with associated complications
  • PTX, hemorrhage, line sepsis
  • Caution in pts with sepsis, hypotension may lead
    to increased bleeding and cardiac arrhythmias

36
Management
  • IVIG
  • 0.4gm/kg/day x 5 days
  • Easily administered and widely available
  • Long duration of action
  • May last as long as 30 days
  • Side effects
  • Anaphylaxis in IgA deficiency
  • Renal failure, pulmonary edema
  • Aseptic meningitis
  • Thrombotic complications and stroke

37
MG Overall Treatment Summary
  • 1. Mild weakness cholinesterase inhibitors
  • 2. Moderate-marked localized or generalized
    weakness
  • Cholinesterase inhibitors, and
  • Thymectomy for patients under age 50-60 yrs
  • 3. Symptoms uncontrolled on cholinesterase
    inhibitors
  • Prednisone if severe or urgent
  • Azathioprine
  • Prednisone failure
  • Excessive prednisone side-effects
  • 4. Plasma exchange or IV Ig
  • Impending crisis crisis
  • Pre-operative boost
  • Chronic disease refractory to drug therapy
  • 5. If above fails
  • Search for residual thymus tissue
  • Cyclosporine or mycophenylate mofetil
  • (Sem. Neurol., 200121425-440)

38
Guillain-Barre Syndrome
39
GBS
  • Most common cause of acute and subacute
    generalised paralysis
  • Incidence of 0.4 to 1.7/100 000 per yr
  • Worldwide, all ages, both sexes
  • Preceding mild resp or GI infection in 60 (1-3
    wks)
  • Campylobacter jejuni (26),
  • CMV, EBV, VZV
  • Influenza, cocksackie, hepatitis A and B, HIV
  • May also be preceded by
  • Surgery
  • Immunisations

40
Typical Symptoms Signs
  • Sensory
  • Paresthesias and slight numbness distally
    earliest Sx
  • Reduced proprioception and vibration sense (1 wk)
  • Motor
  • Weakness
  • Evolves symmetrically over days to 1-2 weeks
  • Usually LE before UE, proximal distal
  • /- trunk, intercostal, neck, cranial muscles
  • Progresses to total motor paralysis and
    respiratory failure in 5 of cases

41
Typical Symptoms Signs
  • Reflexes
  • Reduced and then absent
  • Autonomic dysregulation
  • Sinus tachycardia/bradycardia, facial flushing,
    labile BP, excess or loss of sweating, urinary
    retention
  • Usually do not persist for gter 1 wk
  • Other
  • Myalgias (50) in hips, thighs, back

42
Variants
  • Fisher syndrome
  • Ophthalmoplegia, ataxia, areflexia
  • /- bilateral facial nerve paresis
  • Associated with anti-GQ1b Ab
  • Acute motor sensory axonal neuropathy (5 of GBS
    cases)
  • Severe and diffuse axonal damage
  • Abrupt and explosive onset
  • Severe paralysis, minor sensory features
  • Slow and poor recovery
  • Pandysautonomia
  • Severe orthostatic hypotension, anhidrosis, dry
    eyes and mouth, fixed pupils, arrhythmia,
    bowel/bladder dysfunction
  • Areflexia without somatic motor/sensory
    involvement
  • Other variants
  • Initial cervico-brachial-pharyngeal muscle
    involvement
  • Generalised ataxia without dysarthria or
    nystagmus
  • Facial and abducens weakness, distal
    paresthesias, proximal leg weakness

43
Laboratory Findings
  • Most important CSF, EMG
  • CSF
  • Normal pressure
  • Protein
  • Early (1st 2 days) Usually normal (gt85)
  • Later High (66 in 1st week, 82 in 2nd week)
  • Amount not correlated with clinical course or
    prognosis
  • Acellular or few lymphocytes
  • 10 10-50 lymphocytes, decreases over 2-3 days
    if not other Dx
  • Oligoclonal bands (10-30)

44
Laboratory Findings
  • EMG
  • Abnormalities seen within first week of sx
  • Reduction in motor amplitude
  • Slowed conduction velocities
  • Conduction block in motor nerves
  • Prolonged distal latencies (distal conduction
    block)
  • Prolonged/absent F-responses (involvement of
    proximal parts of nerves and roots)

45
Laboratory Findings
  • Hematology
  • Abnormal only with infection or other disorder
  • Biochemistry
  • Mild-severe SIADH in 7-26
  • Liver enzymes
  • Elevated lt10 reflecting CMV or EBV infection
  • ESR Normal unless co-existing process

46
Diagnostic Criteria
  • National Institute of Neurological Disorders and
    Stroke (NINDS) criteria are based on expert
    consensus.
  • Required features include
  • Progressive weakness of more than one limb,
    ranging from minimal weakness of the legs to
    total paralysis of all four limbs, the trunk,
    bulbar and facial muscles, and external
    ophthalmoplegia
  • Areflexia. While universal areflexia is typical,
    distal areflexia with hyporeflexia at the knees
    and biceps will suffice if other features are
    consistent.
  • Supportive features include
  • Progression of symptoms over days to four weeks
  • Relative symmetry
  • Mild sensory symptoms or signs
  • Cranial nerve involvement, especially bilateral
    facial nerve weakness
  • Recovery starting two to four weeks after
    progression halts
  • Autonomic dysfunction
  • No fever at the onset
  • Elevated protein in CSF with a cell count lt10 mm3
  • Electrodiagnostic abnormalities consistent with
    GBS

47
Differential Diagnosis
  • Features suggesting another diagnosis
  • Sensory level, severe bladder or bowel
    dysfunction ? Spinal cord syndrome
  • Marked asymmetry ? Mononeuritis
    multiplex/vasculitis
  • CSF pleocytosis ? Infectious disorders viral,
    HIV, lyme, poliomyelitis
  • Very slow nerve conduction velocities, multiple
    relapses or chronic course -gt CIDP
  • Persistent abdominal pain and psychiatric signs ?
    Acute intermittent porphyria

48
Management
  • General
  • Recommend admission for observation
  • Can deteriorate rapidly in first days of
    presentation
  • MM Respiratory failure, dysautonomia
  • 25 will require mechanical ventilation
  • Respiratory
  • Measure MIP/MEP/FVC
  • Decision to intubate should be based on downward
    trend
  • Other measures of respiratory status same
  • Counting to 20, strength of NF

49
Management
  • Dysautonomia
  • 10 develop hypotension
  • Volume, /- pressors
  • Hypertension
  • IV labetolol
  • Other complications
  • Adynamic ileus
  • PE
  • Aspiration

50
Management
  • PLEX and IVIG
  • No difference in efficacy between the two
  • Indications for prompt initiation
  • Respiratory failure
  • Bulbar involvement
  • Inability to walk without assistance
  • Usually see these signs day 5-10
  • May occur anywhere from day 1 week 3
  • Steroids
  • No proven benefit

51
PLEX
  • Regimen 4-6 treatments on alternate days
  • Established usefulness in evolving phase
  • If treated within 2 wks onset
  • Decrease in LOS, ventilation, time to independent
    ambulation by approx. half
  • Value less clear if started later than 2 wks
    after initial symptoms
  • Predictors of response
  • Age
  • Preservation of motor CMAP amplitudes pre-PLEX

52
IVIG
  • Dose 0.4 gm/kg/day x 5 consecutive days
  • Cheaper, easier to administer
  • Rare complications
  • Renal failure, proteinuria, pulmonary edema
  • Asceptic meningitis
  • Anaphylaxis in IgA deficiency

53
Course and Prognosis
  • Progressive symptoms 1-4 weeks
  • Plateau 2-4 weeks
  • Recovery A few weeks to months
  • Recurrence 5-10
  • Mortality
  • 3-5
  • Cardiac arrest, ARDS, PTX, HemoTX, PE
  • Pronounced disability 10
  • Clinical prognostic indicators
  • Greater age
  • Rapid evolution early and prolonged ventilatory
    assistance, rapid course
  • Lack of treatment with IVIG or plasma exchange
  • Laboratory
  • EMG severely reduced CMAP and widespread
    denervation

54
Pathogenesis
  • Most evidence points to cell-mediated immunologic
    reaction directed at peripheral nerve
  • May be precipitated by antecedent infection
  • Antibodies against myelin components with
    complement-mediated damage
  • T cells and macrophages become involved in
    process and lead to destruction of myelin/axon

55
Thank you
About PowerShow.com