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Myasthenia Gravis – Questions With Complete Answers
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Myasthenia Gravis – Questions With Complete Answers
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Myasthenia Gravis – Questions With Complete AnswersThis is a disease of Right Ans - • Diseases of neuromuscular junction
o Diseases of muscle excitability
o This is too little excitability
o IMMUNE disease of muscle excitability
Key features of MG Right Ans - Fluctuating weakness of voluntary
(skeletal) muscles primarily those innervated by the motor nuclei of the
brainstem, i.e., ocular, masticatory, facial, deglutitional and lingual.
Weakening during continued activity, quick restoration of power with rest,
dramatic improvement in strength following anticholinesterase drugs.
Immune Disease in which circulating antibodies against components of the
motor post-synaptic membrane
Special vulnerability of NMJ in certain muscles
Immune process in MG Right Ans - IgG 1 and 3 circulating antibodies
against components of the motor post-synaptic membrane
• much of what we kno about autoimmunity is derived from the Hx of this
disorder
Inflammatory response Right Ans - In ALS, there was no inflammatory
process
In MG, IgG1 & 3 invoke a cytokine response -> can see inflammatory response
• THIS IS NOT A DEGENERATIVE DISEASE
• THIS IS A DISEASE OF AUTOIMMUITY
Removing what organ makes the disease better Right Ans - Thymus
Initial presentation: Right Ans - Eye lid, eye movement >face, jaws, throat,
neck>limb and respiratory
,Ocular involvement Right Ans - Ocular palsies or ptosis in ~50% and
eventually ~90% involvement
-- eventually many ppl go to on to develop generalized myasthenia: all
muscles of body involved
recti muscles are the smallest and least number of nerves and nerve fibers
innervated == recti muscles
• This explains the propensity of ocular manifestations of MG :
opthalmoplegia, dipoplia caused by weakness or paresis of the eye muscles,
levator palpebrae and ocular muscles and orbiqularis oculi are involved
Most common presentation Right Ans - occular manifestations
Usually earliest presentatin Right Ans - Occular manifestaitons
o Ppl with generalized mG had or started with ocular involvement
Diplopia Right Ans - Diplopia inconsistent with CN 3, 4, 6 problems
What is the clinical conundrum of ocular manifestaitons in MG? Right Ans -
Symptoms are not consistent with CN 3, 4, 6 problems becuase
pupils are normal!
if CN3 was damaged, there would be pupillary problems
Spread of MG Right Ans - Spreads insidiously to limbs and axial muscles
Facial involvement Right Ans - Muscles of facial expression, mastication,
swallowing, speech affect 80% of patients at some time and 5-10% are the
initial muscles.
Less frequent involvement Right Ans - Less frequent: neck flexors and
extensors, shoulder girdle, hip flexors
, Of trunk muscles, which are more often affected? Right Ans - erector spinae
more often affected.
Most advanced cases: Right Ans - all muscles including diaphragmatic,
abdominal and intercostal, external sphincters of bladder and bowel.
Ocular signs Right Ans - - Sustained upgaze 30 seconds worsens ptosis
(o This is a disease of fatigue. So with sustained contraction of a muscle, it
becomes weaker )
- Cogan's Sign (twitch upper lid when moving eyes from downward position
to neutral)
- Repeated ocular versions or optokinetic stimulus discloses paresis
♣ optokinetic strip is red and white
• to fatigue someones eyes, have pt follow the strip as you move it back and
forth --> fatigues the eyes
- Subtle ptosis of eye when elevating more symptomatic eyelid
- Worse with bright sun, better with cold (pack)
Cogan's Sign Right Ans - twitch upper lid when moving eyes from
downward position to neutral
What makes ocular ptosis better? Right Ans - Cold pack
• clinical manifestation due to weakness of muscles around mouth Right
Ans - o snarl for a smile
o jaw sag (gets better after Tx with ACh esterase inhibitor)
Functional history Right Ans - Arising from chair
Climbing stairs
Eating/jaw fatigue
Head/neck fatigue
Fixing hair, makeup, curling iron,
Lipstick (unable to purse and roll lips)
Unable to control flatus
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