THAISE AGRA TEIXEIRA

GENERALIDADES
THAISE AGRA TEIXEIRA

QUADRO CLINICO
 FRAQUEZA MUSCULAR FLUTUANTE
 FADIGABILIDADE
 MUSCULATURA ESQUELETICA ESTRIADA
THAISE AGRA TEIXEIRA

QUADRO CLINICO
 ENVOLVIMENTO MUSCULAR
▪ MUSCULOS OCULARES
▪ MEMBROS
▪ EXTENSORES DO PESCOÇO
▪ TRONCO
THAISE AGRA TEIXEIRA

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)

CLASSIFICAÇÃO
THAISE AGRA TEIXEIRA

CLASSIFICAÇÃO
 ETIOLOGICA
▪ AUTOIMUNE ADQUIRIDA
▪ NEONATAL TRANSITORIA
▪ MEDICAMENTOSA
▪ CONGENITA
THAISE AGRA TEIXEIRA

CLASSIFICAÇÃO
 ETIOLOGICA
▪ MEDICAMENTOSA
THAISE AGRA TEIXEIRA
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.

FATORES QUE PIORAM QUADRO CLINICO
 CALOR
 ESTRESSE
 INFECÇÃO
 HIPERTIREOIDISMO
 GRAVIDEZ
 ALTERAÇÕES K/Ca
THAISE AGRA TEIXEIRA

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.

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.

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.
 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
THAISE AGRA TEIXEIRA
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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
THAISE AGRA TEIXEIRA

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
THAISE AGRA TEIXEIRA
 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
THAISE AGRA TEIXEIRA
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.
THAISE AGRA TEIXEIRA
 DIAGNOSTICO LABORATORIAL
 Single fibre electromyography
▪ Most sensitive test. Needs costly equipment, not
specific
THAISE AGRA TEIXEIRA
Single-fiber electromyography
showing so-called jitter phenomenon
(second action potential wave group).
THAISE AGRA TEIXEIRA
 DIAGNOSTICO LABORATORIAL
 Anti-MuSK antibodies
▪ Found in a subset of seronegative myasthenia gravis.
Only recently described; not widely available yet
THAISE AGRA TEIXEIRA

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
THAISE AGRA TEIXEIRA

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
THAISE AGRA TEIXEIRA
CT scan of chest showing an
anterior mediastinal mass
(thymoma) in a patient with
myasthenia gravis.
THAISE AGRA TEIXEIRA
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.
THAISE AGRA TEIXEIRA
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.
THAISE AGRA TEIXEIRA

TRATAMENTO
 ANTICOLINESTERASICOS
 IMUNOSSUPRESSORES
▪
▪
▪
▪
▪
CORTICOIDES SISTEMICOS
AZATOPRINA
CICLOSPORINA
METOTREXATO
CICLOFOSFAMINA
 TIMECTOMIA
 PLASMAFERESE
 IMUNOGLOBULINA
THAISE AGRA TEIXEIRA

TRATAMENTO
 ANTICOLINESTERASICOS
neostigmine
piridostigmine
edofrônio
Efeitos dos anticolinesterásicos
Bradicardia
Hipotensão
Secreções excessivas
Broncoconstrição
Sufocamento
Hipermotilidade gastrintestrinal
Redução da pressão intra-ocular
Miose
THAISE AGRA TEIXEIRA

TRATAMENTO
 IMUNOSSUPRESSÃO
▪ CORTICOIDES SISTEMICOS
▪ AZATIOPRINA
▪ CICLOSPORINA
▪ METOTREXATO
▪ CICLOFOSFAMINA
THAISE AGRA TEIXEIRA

TRATAMENTO
 TIMECTOMIA
THAISE AGRA TEIXEIRA

TRATAMENTO
 PLASMAFERESE
 IMUNOGLOBULINA
THAISE AGRA TEIXEIRA
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