Myasthenia Gravis Flashcards
What is it?
Pathophysiology
What is associated with MG in young females?
What is associated with MG in elderly males?
A long-term neuromuscular disease that leads to varying degrees of skeletal muscle weakness.
Autoimmune disease - SLE, RA + thymic hyperplasia
Thymic atrophy or thymoma
Symptoms:
Fatigabilty muscle weakness usually in the following order:
- Extraocular - 2 presentations
- Bulbar - 3 presentations
- Smiling - 1
- Neck
- Limb-girdle i.e. proximal weakness
- Trunk
Ptosis and diplopia
Dysarthria
Dysphonia
Dysphagia
Myasthenic snarl on smiling
Exacerbating factors:
What type of illness may make it worse?
What reduced electrolyte makes it worse?
Physiological stress can make it worse. Give some examples?
Infection
Hypokalaemia
Pregnancy
Emotion
Exercise
Signs:
What is fatigability?
2 ways to test for it?
How can ptosis be tested for?
WHAT IS NORMAL COMPARED TO OTHER NEUROLOGICAL CONDITIONS?
Muscle gets weaker the longer exercise/exertion is done
(1) Cannot hold eyes in upward gaze for more than a few seconds
(2) The voice becomes quiet on counting to 50
Weak forced eye closure + it is easily overcome
NORMAL REFLEXES, BULK, TONE AND SENSATION!
Investigations:
The only test that can be used to diagnose?
What other test can be done if above is negative?
What may be used to show gradually reducing muscle response?
What is the ice test and why is it done?
Anti-AChR antibody testing
MuSK (muscle-specific kinase) if above is negative?
An EMG
An ice pack is applied to the closed eyelid for 2-5 minutes.
Ptosis improves in MG!
Management:
What is Pyridostigmine? MOA?
Side effects?
Cholinesterase inhibitors
It decreases the metabolism of ACh, increasing the cholinergic effect at the NMJ.
Cholinergic side effects - salvation, lacrimation, sweats, miosis, diarrhoea and vomiting, colic
Relapses - what is used?
Immunosuppression - prednisolone, azathioprine, methotrexate
What should be checked in both males and females?
What can be done in treatment-resistant MG?
Thymoma or thymic hyperplasia
Thymectomy
Prognosis?
Normal life expectancy for most
Relapsing-remitting course
