Myaesthenia Gravis in Pregnancy.

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Myaesthenia Gravis in Pregnancy.

• Dr. Mridula A. Benjamin
• Dept of Obs and Gyn,
• RIPAS Hospital, Brunei

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M.J. IC31-001064

• 22 yrs. G2P1.
• Self conception. Non consanguineous.
• 1st preg
• LMP ? July 2004.
• Unbooked case.
• Emergency LSCS was done in Jan 2005 at 30
  wks for severe APH.
• No significant past medical and family
  history.

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• 24/09/05 AE for sore throat, loss of voice,
  unable to swallow and sweating.
• BP 96/58 mm.Hg.
• ENT Diagnosed fx. Aphasia after normal
  fibroscopy.
• 25/09 Chest review Ocular fatigue and facial
  diaplegia. No obvious motor weakness.
• Combined resp and metab acidosis.
• 26/09 Neuro review Patient dyspnoiec,
  tachycardic.
• ANA, Anti-DNA, Tensilon test

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• ANA- Mixed homogenous 140.
• Anti-DNA Negative. Tensilon test
  Positive.
• Repetitive test ve. EMG Muscle
  weakness.
• Diagnosed as Myas. Crisis.
• Treated with pyridostigmine, prednisolone and
  Azathioprine.
• Discharged from Neuro on 15/10.
• Referred by Neuro to OG on 29/10 for pregnancy
  after stopping Azathioprine.

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• Seen in OG on 09/11.
• LMP 29/Aug/05. EDC 6/6/6
• USS 10 wks pregnant.
• Advised to continue pyridostigmine and
  prednisolone.Given folic acid, adv NT
• Booked into high risk clinic on 22/11.
• Antenatal screening NAD.
• Regular follow ups. Normotensive

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• USS at 18 wks No anomalies.
• Subsequent USS at 30, 35 and 37 wks showed
  adequate growth.
• USS on 16/05 Fetal wt of 3059 gms and AFI of 13.
  Placenta posterior and upper segment.
• Paeds counselling on 16/05 Told about resp.
  insuff. requiring ventilation, feeding
  difficulties, congenital MG.

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• Admitted with tightenings on 29/05/06.
• Counselled for VBAC.
• Neuro review was done with adv. of Inj
  Hydrocortisone 100mg 6 hrly in active labour.
• On 31/05 SROM at 140 am.
• Contractions 1 5 40, CTG-R.
• VE os 1.5, thick cervix, liquor clear, memb
  absent, stn high.
• Was given sedation.

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• Reviewed by on call team morning.
• Anaemic, Hb 7.8, given PCV.
• In view of prolonged latent phase, MG, prev.
  LSCS, high presenting part, LSCS done.
• Post operative uneventful. Started on medication.
• Discharged on day 5 after neuro review.

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Myasthenia gravis

• Autoimmune neuromuscular disease characterized by
  weakness and fatigue of the skeletal muscles.
• Female-to-male ratio is 21.
• Usually affects women in third decade of life.
• Worldwide prevalence 40 cases per million.
• Incidence is 1 in
  20,000-40,000.

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Pathology

• Production of autoantibodies against human
  acetylcholine receptors (AChRs), usually
  immunoglobulin G.
• This is detected in as many as 90 of patients.
• Antibodies interfere with the conduction of
  impulses across myoneural junctions by decreasing
  the number of available AChRs at neuromuscular
  junctions.

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In pregnancy

• Course during pregnancy is hard to predict.
• Patients may have disease exacerbation (40),
  remission(30), or no change (30).
• Pregnant patients face risks of exacerbation,
  respiratory failure, adverse drug response,
  crisis, and death.
• Worsens by emotional distress, systemic illness
  and hot temperature.

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Maternal complications

• 20 of patients experience respiratory crisis
  that require mechanical ventilation.
• Association between MG and preeclampsia. Altered
  immune status could be an etiologic factor in
  preeclampsia. MgSO4 is contraindicated.
• Bone marrow suppression.
• Hydramnios

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Contd.

• Complicated labor Although smooth muscle is not
  affected by autoantibodies and the uterus is not
  compromised, the second stage of labor involves
  striated muscle. The patient may become exhausted
  during labor and may require assistance. Forceps
  delivery has been recommended.
• Myaesthenia crisis can occur Parenteral
  drugs.

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Fetal complications

• Fetal abnormalities pulmonary hypoplasia and
  arthrogryposis.
• Premature delivery occurs in 36.5 of cases. B
  sympathomimetics can be used.
• Growth restriction.
• Still births (2.7) and miscarriages (4.7).
• Neonatal MG Rates10-20
• Does not appear at birth.
• Usually temporary, lasting only a few weeks.

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Plauche et al

• Exacerbations occurred in approximately 41 of
  patients during pregnancy and in 29.8 of
  patients postpartum.
• Approximately 4 of patients died because of
  worsening of the disease or because of treatment
  complications.

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Batocchi et al

• 60 of exacerbations occurs during the first
  trimester.
• 28 of patients deteriorates immediately after
  delivery.
• Premature delivery occurs in 7.4 patients.
• Caesarean delivery is performed in 30.
• No correlation between MG severity before and
  during pregnancy.

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History

• Symptoms ptosis, diplopia, breathing difficulty,
  dysphagia, and weak limbs.
• Intermittent ptosis and diplopia are usually the
  initial reported symptoms.
• Symptoms become generalized within 1 year and
  fluctuate in severity.
• Worsen with exertion, emotional distress and
  systemic illness and are relieved with rest.

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Physical examination

• Muscle strength assessed by quantitative studies
  eg. patient squeeze the examiner's hand
  repeatedly, flex her arm against resistance,
  asking the patient to smile.
• Deep tendon reflexes are preserved.
• Check for diplopia and ptosis.

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Differential diagnosis

• Eaton-Lambert myasthenic syndrome.
• Botulism.
• Hyperthyroidism.
• Neurasthenia.
• Intracranial mass lesion.
• Progressive external ophthalmoplegia.
• Drug-induced MG.

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Tests

• Screen for other autoimmune diseases.
• Test of choice Tensilon test IV injection of
  edrophonium (cholinesterase inhibitor). This
  increases the amount of ACh available. Clinical
  improvement occurs in 10-60 seconds and lasts for
  approximately 10 minutes.
• Most specific test Anti-AChR antibody levels.
• EMG Reduced evoked muscle potential.
• CT scans For the thymus.

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Drugs to avoid

• Narcotics, tranquilizers, barbiturates.
• Inhalation anesthetics (ie, halothane,
  trichloroethylene, ether).
• Magnesium and lithium salts.
• Penicillamine.
• Beta-adrenergic agents.
• Aminoglycoside antibiotics, neomycin,
  tetracycline, lincomycin.

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Management

• Individualized therapy by neurologist and an
  obstetrician/gynecologist during pregnancy.
• Crisis can occur due to worsening disease
  processes, reduced effects of anticholinesterase
  drugs, or overdose of anticholinesterase
  medication.
• Management of myasthenic crisis requires careful
  monitoring. ABG values must be monitored in
  patients with increasing weakness.

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• Patient has to be seen every 2 wks in the 1st 2
  trimesters and every week in 3rd.
• Avoid undue physical and emotional stress.
• Exacerbating drugs to be avoided.
• Drug doses may have to be altered due to maternal
  and physiological changes.
• RTI and UTI are to be treated aggressively.
• Be wary of preterm labour.
• Early decision on anaesthetic options.

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Medications

• Anticholinesterase muscle stimulants
• Preferred treatment. Reportedly safe in
  pregnancy. Eg. Neostigmine, pyridostigmine.
• Corticosteroids
• Prednisolone is fairly safe during
  pregnancy. Patients who wish to become pregnant
  are recommended to get pregnant while in
  steroid-induced remission.
• Can lead to PROM.

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Medications contd.

• Immunoglobulin
• 0.4 g/kg/d IV for 5 consecutive days.
  Improvement is noticeable in 3-21 days and lasts
  as long as 3 months.
• Antimetabolites
• Azathioprine, cyclosporine. Unsafe in
  pregnancy.

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Plasmapheresis

• Very effective. Consists of 3-6 exchanges of 2-3
  L over 1-2 weeks.
• Can result in premature delivery because of large
  hormone shifts.
• Complications from hypovolemic reactions or
  allergies.
• Expensive.
• Surgery
• Thymectomy done in young patients before preg.

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Labour mx.

• Caesarean Reserved only for necessary cases.
• Not depressing respiration is important.
• Regional anesthesia is good for abdominal
  delivery.
• Epidural Used to decrease systemic medications
  and provide anesthesia for outlet forceps.

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Summary

• Pre pregnancy
• Counselling about risks
• Review of therapy
• Consider thymectomy

• Prenatal
• Joint Obs and Phy care
• Continue Anticholinesterase, steroids and
  azathioprine
• Plasmapheresis in drug resistant cases
• Fetal surveillance
• Avoid stress

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• Labor/Delivery
• Minimize stress
• Continue anticholinesterase drugs
• Steroid cover
• Regional analgesia preferable to narcotics GA
• Assisted 2nd stage likely
• Avoid MgSO4 in preeclampsia

• Postnatal
• Review drug doses
• Care and surveillance of newborn. May need short
  term anticholinesterase

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