Question 5

College answer

Most candidates had a superficial understanding of myaesthenia gravis and myaesthenic crisis. Candidates who scored well were familiar with the pathogenesis of the disease and the triggers and treatments. However, even those candidates who referred to specific challenges such as fatiguability, bulbar dysfunction and secretion burden in the management section, often did not give a detailed discussion of how to manage these. Most candidates mentioned pyridostigmine and/or neostigmine, IVIG, plasma exchange, steroids and/or other immunosuppressants, and therefore scored well for part (a) (which was worth 50%).

Discussion

They said "list" the interventions, a syllabus keyword which conventionally does not invite very much discussion; and for 30% of the marks you'd really only be expected to produce a short point-form list:

• Specific interventions include:
  • First line:
    • Plasmapheresis, or IV immunoglobulin
    • High dose steroids (prednisolone 1.0-1.5mg/kg/day)
  • Second line
    • Pulse steroids (1g methylprednisolone)
    • Steroid-sparing agents (azathioprine, mycophenolate)
    • Immune suppression (rituximab, cyclophosphamide)
    • Complement deactivation (eculizumab)
  • Acetylcholinesterase inhibitors (pyridostigmine)
  • Thymectomy 

The list of drug classes that exacerbate myasthenia gravis include multiple different antibiotic classes, which - presumably- would have all counted individually

• Antibiotics:
  • Aminoglycosides
  • Macrolides
  • Fluoroquinolones
• Beta-blockers
• Immune checkpoint inhibitors (ipilimumab, pembrolizumab, atezolizumab, and nivolumab)
• Statins

There is also a list of miscellaneous classless drugs that can trigger myasthenia exacerbations, and it is not clear what would have happened if the trainees had mentioned these:

• Iodinated contrast media
• Live attenuated vaccines
• Procainamide
• Hydroxychloroquine
• D-Penicillamine
• Desferrioxamine

• Challenges to the extubation of a myasthenia gravis patient (and methods to address them):
  • Weakness (pyridostigmine)
  • Cholinergic side effects, increased secretions (propantheline)
  • Critical illness and steroid myopathy (dietary protein supplementation, physiotherapy, early mobility, use of steroid-sparing agents such as mycophenolate)
  • Poor swallow or cough (tracheostomy as a bridge to future normal bulbar function)
  • Slow weaning (so, extubate on to NIV)
  • Marginal respiratory reserve (so, optimise VAP and CCF therapies before contemplating extubation)

An excellent paper on weaning the patient with neuromuscular disease was published by Torres-Castro et al in 2021, and likely served as the origin for this SAQ. Even though they did not find any papers that fit their inclusion criteria, they discuss the options in some detail, and the ideas in that paper were amalgamated into the table above.