MIASTENIA GRAVESTHAISE AGRA TEIXEIRA
MIASTENIA GRAVES
GENERALIDADES
THAISE AGRA TEIXEIRA
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QUADRO CLINICO FRAQUEZA MUSCULAR FLUTUANTE FADIGABILIDADE MUSCULATURA ESQUELETICA ESTRIADA
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QUADRO CLINICO ENVOLVIMENTO MUSCULAR
▪ MUSCULOS OCULARES▪ MEMBROS▪ EXTENSORES DO PESCOÇO▪ TRONCO
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CLASSIFICAÇÃO IDADE
▪ NEONATAL – 10-15% sintomatico▪ ADULTO
ANTICORPOS ANTI-AchR▪ POSITIVO
▪ 85% GENERALIZADA▪ 50-60% OCULAR
▪ NEGATIVO-10-20% ▪ ANTICORPOS ANTI- MUSK(muscle specific protein
kinase)
MIASTENIA GRAVES
CLASSIFICAÇÃO
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CLASSIFICAÇÃO ETIOLOGICA
▪ AUTOIMUNE ADQUIRIDA▪ NEONATAL TRANSITORIA▪ MEDICAMENTOSA▪ CONGENITA
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CLASSIFICAÇÃO ETIOLOGICA
▪ MEDICAMENTOSA
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Schema of normal neuromuscular junction.
Thanvi B R , Lo T C N Postgrad Med J 2004;80:690-700
Copyright © The Fellowship of Postgraduate Medicine. All rights reserved.
Schema of neuromuscular junction in myasthenia gravis (note: widened synaptic cleft, reduced number of acetylcholine receptors, and simplification of postsynaptic membrane).
Thanvi B R , Lo T C N Postgrad Med J 2004;80:690-700
Copyright © The Fellowship of Postgraduate Medicine. All rights reserved.
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FATORES QUE PIORAM QUADRO CLINICO CALOR ESTRESSE INFECÇÃO HIPERTIREOIDISMO GRAVIDEZ ALTERAÇÕES K/Ca
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Box 1: Characteristic clinical features of myasthenia
gravis
Ocular muscle weakness is usually the initial presentation
and may be the only feature throught the course in about
10% of patients. The ptosis (and diplopia) is exacerbated
by the prolonged upward gaze toward a fixed target for one
minute.
In most cases, weakness progresses from ocular muscles to
involve other muscles in a craniocaudal direction. The
weakness of intercostal muscles and diaphragm leads to
dyspnoea on exertion or at rest. The orthopnoea with rapid
resolution on sitting up and diaphragmatic paradox are
important clinical signs of neuromuscular breathlessness.
MIASTENIA GRAVES
Box 1: Characteristic clinical features of myasthenia
gravis
Ocular muscle weakness is usually the initial presentation
and may be the only feature throught the course in about
10% of patients. The ptosis (and diplopia) is exacerbated
by the prolonged upward gaze toward a fixed target for one
minute.
In most cases, weakness progresses from ocular muscles to
involve other muscles in a craniocaudal direction. The
weakness of intercostal muscles and diaphragm leads to
dyspnoea on exertion or at rest. The orthopnoea with rapid
resolution on sitting up and diaphragmatic paradox are
important clinical signs of neuromuscular breathlessness.
MIASTENIA GRAVES
Box 1: Characteristic clinical features of myasthenia
gravis
Deep tendon reflexes are intact or may be brisk.
There are no objective sensory deficits.
In severe cases, respiratory failure may ensue, needing
intubation and mechanical ventilation.
Symptoms may fluctuate and there may be remissions of
variable periods, particularly at early stages.
MIASTENIA GRAVES
DIAGNOSTICO LABORATORIAL
Edrophonium (Tensilon test
▪ Easy to administer, no need for expensive
equipment. Limitations: false positives and false
negatives, occasional serious side effects, for
example, hypotension and arrhythmias
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DIAGNOSTICO LABORATORIAL
Ice test
▪ Nearly 80% sensitive and highly specific to diagnose
myasthenic ptosis, no need for cardiac monitoring,
can be done in an office setting. Not commonly used,
applicable only when ptosis is present
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DIAGNOSTICO LABORATORIAL
AChR antibody in serum
▪ Nearly 80%–85% sensitive in generalised and 60%–70% in
ocular myasthenia gravis, highly specific, non-invasive, now
widely available. May be the diagnostic “gold standard”.
Titres do not always correspond with the severity of
myasthenia gravis
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DIAGNOSTICO LABORATORIAL
Repetitive nerve stimulation
▪ Sensitivity around 75%. Uncomfortable to patient,
not specific. Not reliable if the limb is cold, or
patient on acetylcholinesterase inhibitors
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A typical recording of compound muscle action potentials with repetitive nerve stimulation at low frequency in a patient with myasthenia gravis. Note the gradual decline in the amplitude of the compound muscle action potential with slight improvement after the fifth or sixth potential.
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DIAGNOSTICO LABORATORIAL
Single fibre electromyography
▪ Most sensitive test. Needs costly equipment, not
specific
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Single-fiber electromyography showing so-called jitter phenomenon (second action potential wave group).
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DIAGNOSTICO LABORATORIAL
Anti-MuSK antibodies
▪ Found in a subset of seronegative myasthenia gravis.
Only recently described; not widely available yet
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DIAGNOSTICO LABORATORIAL
Computed tomography/MRI of chest
▪ To diagnose associated thymic tumours. Non-invasive.
Greater yield in patients >40 years of age. May be used
post-thymectomy to look for residual thymic tissue in
patients who deteriorate unexpectedly
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DIAGNOSTICO LABORATORIAL
Computed tomography/MRI of chest
▪ To diagnose associated thymic tumours. Non-invasive.
Greater yield in patients >40 years of age. May be used
post-thymectomy to look for residual thymic tissue in
patients who deteriorate unexpectedly
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CT scan of chest showing an anterior mediastinal mass (thymoma) in a patient with myasthenia gravis.
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Cogan sign. Patient changes gaze from downward position (A) to primary position (B). Both lids are seen to overshoot in twitch (B) before gaining their initial ptotic position (D). In this case, Cogan sign is seen more obviously on right, whereas left lid is more ptotic.
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Increasing left ptosis developing upon sustained upward gaze in patient with myasthenia gravis (A through F). Note limited elevation of left eye, denoting superior rectus palsy (A). A initially, C after around 20 seconds, F after 1 minute.
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TRATAMENTO ANTICOLINESTERASICOS IMUNOSSUPRESSORES
▪ CORTICOIDES SISTEMICOS▪ AZATOPRINA▪ CICLOSPORINA▪ METOTREXATO▪ CICLOFOSFAMINA
TIMECTOMIA PLASMAFERESE IMUNOGLOBULINA
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TRATAMENTO ANTICOLINESTERASICOS
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Efeitos dos anticolinesterásicos Bradicardia Hipotensão Secreções excessivas Broncoconstrição Sufocamento Hipermotilidade gastrintestrinal Redução da pressão intra-ocular Miose
neostigminepiridostigmineedofrônio
MIASTENIA GRAVES
TRATAMENTO IMUNOSSUPRESSÃO
▪ CORTICOIDES SISTEMICOS▪ AZATIOPRINA▪ CICLOSPORINA▪ METOTREXATO▪ CICLOFOSFAMINA
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TRATAMENTO TIMECTOMIA
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TRATAMENTO PLASMAFERESE IMUNOGLOBULINA
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Figure. (A) A 61-year-old woman with marked generalized myasthenia gravis, 2 days after plasma exchange treatment, with only minimal spontaneous ptosis at baseline.
Toyka K V Neurology 2006;67:1524-1524
©2006 by Lippincott Williams & Wilkins
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