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Myasthenia Gravis GuillainBarre Syndrome

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... at many NMJs manifests as weakness of voluntary muscle-cardinal feature ... Voluntary muscle weakness cardinal feature, with fatigability, relieved with rest ... – PowerPoint PPT presentation

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Title: Myasthenia Gravis GuillainBarre Syndrome


1
Myasthenia GravisGuillain-Barre Syndrome
  • ICU teaching
  • April 27th

2
Myasthenia Gravis
  • Autoimmune disorder
  • Antibodies directed against acetylcholine
    receptor (AChR)
  • Best understood clinical disorder of
    neuroreceptor function.
  • Clinically characterised by weakness and
    fatigability on sustained effort
  • Intensive care required due to severe involvement
    of bulbar and respiratory muscles

3
incidence
  • 1 in 20 000
  • No racial or geographical prediliction
  • Any age although rare in lt2yrs
  • Peaks incidence in young females
  • Females x2 males
  • Gender preference diminishes with increasing age
  • Smaller second peak in elderly males

4
Pathophysiology
  • IgG AB interact with the postsynaptic AChR at the
    nicotinic neuromuscular junction(NMJ).
  • This reduces the number of functional receptors
    by blocking Ach attachment, by increasing the
    degradation of receptors and by complement
    induced damage to the NMJ
  • MG pts have a reduced AChR density and have 30
    the normal number of AChR
  • This reduces the safety margin at the NMJ

5
  • The reduced AChR density leads to decreased
    amplitude in AP in the post synaptic region
    leading to failure in initiation in muscle fibre
    contraction.
  • When it occurs at many NMJs manifests as weakness
    of voluntary muscle-cardinal feature

6
Aetiolgy
  • Antibody mediated, origin uncertain
  • Thymus gland possible generator
  • Gland abnormal in 75 of patients with MG(
    hyperplasia and thymoma)
  • B and T lymphocytes become sensitised to AChR
    found in myoid cells in the gland
  • Reason for breakdown in normal immune tolerance
    uncertain

7
Clinical features
  • Voluntary muscle weakness cardinal feature, with
    fatigability, relieved with rest
  • 15 pts have disease confined to the eyes
  • 85 generalised ocular, facial, bulbar, limb
  • Respiratory muscles affected mildly however in
    myasthenic crisis resp failure requiring support
    may be required
  • Symptoms of diplopia, ptosis, dysarthria,
    regurgitation,dysphagia are all common.

8
Diagnosis and Ix
  • History and examination
  • EMG
  • Recording of compound muscle action
    potentials(CMAP)
  • Following repetitive stimulation of motor nerve
  • In MG this leads to reduction in CMAP (gt10)

9
  • All EMG abnormalities are not specific for MG
  • Detection of anti-AChR antibodies
  • In 80-85 cases and are pathognomonic
  • The Tensilon test-
  • up to 10mg edrophonium is administered IV is
    standard test.
  • Mg pts show marked improvement after 30sec and
    lasts 5min

10
Management
  • Anticholinesterase drugs potentiate the Ach at
    receptor sites, Pyridostigmine most common up to
    60mg QID. Effects diminish over months
  • Thymectomy best results and advocated early in
    all patients regardless of severity or presence
    of thymoma. Earlier remission, lower mortality,
    greater delay in recurrences.

11
Management continued
  • Immunosuppression - corticosteroids mainstay
  • effective in 70
  • best results when used high dose and reduced
  • average of 4months with some indefinitely
  • Azothiprine and methotrexate effective adjuncts,
    80 helped, few remission

12
Mx continued
  • Plasma exchange effective in achieving short term
    remission, for preoperative thymectomy, in
    myasthenic crisis or respiratory failure.
    Reduction in level of antibodies correlates with
    the improvement in muscle power. Improvement seen
    within days and is short lived.five exchanges
    3-4litres each over 2 weeks
  • Iv IG similar effects as plasma exchange ,
    400mg/kg/day for 5days. Some pts get long term
    benefit. No effect on ab numbers and mechanism of
    action unknown.

13
Complications of all treatments
  • Sepsis and infections related to IV catheters and
    immunosuppression
  • Renal failure from IgG and Cyclosporin
  • All the complications of long term steroid use

14
Myasthenic and cholinergic crisis
  • Known MG pts may have life threatening acute
    deteriorations
  • Following infections, pregnancy and
    administration of some drugs
  • Most resolve over several weeks some last months
  • Incidence of M.crisis increases with age

15
Management of the crisis
  • Risk of pulmonary aspiration due to bulbar muscle
    involvement, bacterial pneumonia due to stasis,
    acute resp failure and cardiorespiratory arrest.
  • Resusitation as for any patient
  • Followed by edrophonium, this will indicate
    whether patient will respond to increasing dose
    of anticholinergic drug.

16
  • If edrophonium worsens condition patient
    suffering cholinergic crisis which is due to over
    admin of anticholinesterase drugs( cramps,
    brady,salivation,diarrhoea)
  • Improvement seen if anticholinesterase drugs
    reduced, withdrawn and restarted

17
ICU management
  • Frequent estimations of VC and inspiratory force
  • Consideration of mechanical ventilation given to
    those with severe bulbar and respiratory muscle
    involvement
  • Deterioration of ABGs often late sign
  • Good ICU care, maintaining K, Ca Mg levels
    normal. Physio and NG feeding.
  • If adjustment of medications not sufficient to
    see improvement need to consider high dose
    steroid and plasma exchange therapy.

18
Drugs to avoid
  • Polymyxin group of antibiotics
  • Aminoglycosides
  • B blockers
  • Procainamide, lignocaine
  • Suxamethonium

19
Associated disorders
  • Thyroid abnormality
  • Rheumatoid disease
  • Scleroderma
  • Psoriasis
  • Polymyositis
  • SLE
  • Pernicious anaemia

20
anaesthesia
  • Pre op optimisation
  • Airway assessment if RA
  • Avoid premedication
  • Avoid depolarising mr
  • Reduce dose of non-depolarisers if any used at
    all, monitoring at all times
  • Continue steroid and give additional on day of
    surgery
  • Post op hdu-up to 33 require ventilation
    predicted by long pre-op hx MG, high
    anticholinesterase requirements, VC lt2.9l.

21
Guillain Barre Syndrome
  • Acute demyelinating polyneuropathy
  • Commonest cause of rapid-onset flaccid paralysis
    since polio decline
  • Occurs as an autoimmune response following a GI
    or respiratory infection
  • Potentially severely debilitating disorder
    affecting 1-3 per 100,000
  • 10 die from associated complications
  • A further 10 suffer from long term neurological
    sequelae and physical dependence

22
  • Guillain, Barre and Strohl first described a
    disease affecting French soldiers ( motor
    weakness, areflexia and CSF abnormalities) in
    1916
  • Descriptions date back to 1859 when Laundry
    described ascending paralysis

23
  • Despite well recognized syndrome and potentially
    fatal
  • Often misdiagnosed and subtle signs of
    decompensation missed

24
Aetiology
  • All ages affected with bimodal distribution
    towards young adults and the elderly
  • Slight male preponderance
  • Children less severely affected
  • Most commonly occurs within a month of GI or resp
    upset.
  • Commonest organism is campylobacter
  • Others inc EBV, CMV, complication of HIV

25
  • Have been reports of association with vaccines,
    surgery, epidurals, bone marrow and organ
    transplantation, SLE, lymphoma, sarcoidosis
  • Pregnancy and OCP confer some protection

26
Pathogenesis
  • Immunologically mediated nerve injury
  • Inflammatory cell infiltrates are seen in
    association with the demyelination, which is
    regarded as the primary pathological process
  • Precise mechanism of sensitisation not known
  • Peripheral nerves show infiltration of the
    endoneurium by mononuclear cells in a perivenular
    distribution

27
  • Distributed throughout the nerve length but
    focused at nerve roots, spinal nerves and major
    plexuses
  • Macrophages actively strip myelin from bodies of
    schwann cells and axons
  • Underlying immune response is complex
  • Effectiveness of plasma exchange and IgG is
    thought to be blocking of demyelinating antibodies

28
Clinical presentation
  • Several distinct clinical pictures described
  • Acute inflammatory demyelinating
    polyradiculopathy (AIDP)
  • Acute motor axonal neuropathy (AMAN)
  • Acute motor sensory axonal neuropathy (AMSAN)
  • Miller-Fisher syndrome ( ataxia, areflexia and
    opthalmoplegia which may be accompanied by limb
    weakness, ptosis and facial and bulbar palsy

29
  • Classical picture is that of ascending limb
    weakness with areflexia, although a purely
    sensory variant has been well documented
  • Features of GBS include
  • Progressive motor weakness, usually ascending
    from the legs
  • Areflexia
  • Facial palsy and bulbar weakness
  • Opthalmoplegia
  • Sensory symptoms

30
  • Severe pain esp girdle
  • Resp muscle weakness
  • Autonomic dysfunction( over or underactivity of
    the SNS or PSNS)

31
Features required for diagnosisdefined by
national institute of neurological and
communicative diseases and strokes
  • Progressive muscle weakness of more than one limb
  • Areflexia or marked hyporeflexia
  • CSF cell counts of no more than 50 monocytes or 2
    polymorphonuclear leucocytes
  • Features highly suggestive
  • Features required to rule out other diagnosis

32
Differential diagnosis
  • Rapidly progressive space occupying lesion eg
    epidural abscess
  • Critical illness polyneuropathy, associated with
    recovery from multiorgan failure, steroids and
    muscle relaxants
  • EMG shows pure axonal degeneration patterns
    compared to demyelination seen in GBS
  • CSF protein level normal in CIP

33
Monitoring
  • Cardiac
  • Blood pressure
  • Vital capacity measured three times a day
  • Bulbar function monitored to prevent aspiration

34
Investigations
  • In over 90 patients CSF protein is raised (
    gt0.4g/l) within a week of onset of symptoms
  • Level does not correlate with clinical findings
  • Nerve conduction studies demonstrate reduced
    conduction velocity
  • Liver and renal function may be impaired
  • Antiganglioside antibody should be searched for

35
  • SIADH may occur in association with GBS
  • Stool cultures for campylobacter
  • Ecgs for QT, T and ST abnormalities
  • Head CT to exclude raised ICP and other pathology
    prior to LP

36
Treatment
  • Major challenge
  • Outcome excellent if complications treated or
    avoided
  • Prevented by meticulous attention to detail

37
Specific treatment-disease modifying modalities
  • Plasma exchange
  • Immunoglobin
  • Both should be used when patient non-ambulatory
    or resp decompensation occurs
  • Both have been examined in RCT and no difference
    in efficacy demonstrated between them

38
Plasma exchange
  • 2 RCT showed reduction in ventilation and reduced
    time to motor recovery
  • Mortality was not altered
  • Most effective within 7 days of onset
  • 3-5 exchanges of 1-2 plasma volumes each over 1-2
    weeks
  • Ffp more complications than albumin
  • CI include CVS instability, sepsis and
    haemostatic problems
  • Side effects are hypotension, hypocalcaemia,coagul
    ation abnormalities and sepsis

39
IV Immunoglobin
  • 0.4mg/kg daily for 5-6 days
  • Easier administration
  • Fewer side effects
  • Commence tx within 2 weeks of onset of symptoms
  • CI include IgA deficiency(anaphylaxis)
  • Renal function may deteriorate
  • Severe congestive cardiac failure major
    contraindication
  • RCT has suggested as effective as plasma exchange

40
Steroids
  • No place in the treatment of GBS
  • RCT have shown no advantage

41
CSF filtration
  • Few case reports
  • When plasmapheresis and IgG have failed
  • Logistics difficult!

42
Supportive care
  • Respiratory,
  • 25 require ventilated
  • Physio and VC monitoring in the spont breathing.
    If less than 15ml/kg or rising pCO2 ventilation
    likely
  • Monitoring of bulbar function for prevention of
    aspiration
  • Non-invasive ventilation often not useful as does
    not eliminate the problem of not being able to
    clear secretions due to poor cough
  • Early tracheostomy should be considered

43
Supportive care
  • Cardiovascular
  • Full invasive monitoring
  • Care with induction of anaesthesia as leads to
    hypotension and arrhythmias
  • Care with suxamethonium may lead to arrhythmias
  • Instability may be worsened by other drugs
  • Autonomic instability common

44
Supportive care
  • Nutrition, fluid and electrolytes
  • Paralytic ileus common
  • Tpn may be required
  • Energy and fluid requirements are reduced in
    these patients
  • Physiotherapy
  • DVT prophylaxis
  • Sepsis survellience
  • Psychological care
  • analgesia

45
Prognosis
  • Death in up to 25 of those who require ICU has
    been reported often from autonomic abnormalities
  • Approx 16 patients suffer permanent disability
  • Those who require ventilation, improve after more
    than 3 weeks, not improved within 1 month have
    greater risk of poorer outcome
  • Gradual improvement may occur over 18months
    -2years
  • Recurrence n 2-5 cases

46
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