Myaesthenia gravis

Question 1

Definition of Myaesthenia

Answer 1

Autoimmune conditiopn affecting nicotinic-acetylcholine receptors at NMJ

Question 2

Signs in Myaesthenia

Answer 2

Bilateral ptosis -> worse on sustained upwards gaze
Complex ophthalmaplegia
Fatiguability
Myaesthenic snarl -> Horizontal smile

Question 3

Investigations in Myaesthenia

Answer 3

Anti-ACh receptor antibodies
Anti-MUSK antibodies (if above negative)
Neurophysiology -> Single fibre EMG - reptitive stimulation shows decremental response
CT thorax -> Thymoma
TFTs -> Underlying graves

Question 4

DDx in Myaesthenia

Answer 4

Miller fisher syndrome
Lambert eaton myaesthenic syndrome

Question 5

Lambert eaton myaesthenic syndrome

Answer 5

Small cell lung cancer
Diminished reflexes that become more brisk with sustained effort
Ix -> VGCC antibodies
EMG -> Second wind phenomenon on reptitive stimulation
Mx: Find underlying malignancy + treat

Question 6

Management of myaesthenia (Acute)

Answer 6

IV immunoglobulin/plasma exchange

Question 7

Management of myaesthenia (chronic)

Answer 7

Supportive:
Assess resp function w/ FVC
SALT - assess swallow
Avoid drugs that worsen MG -> Beta blockers, aminoglycosides

Medical:
Pyridostigmine - anticholinesterase
Steroids - Can cause paradoxical worsening after 2/52
DMARDS - Azathioprine, MTX and MMF