1.4 Myasthenia Gravis II Flashcards
What is myasthenia gravis?
A potentially life threatening auto immune condition
What are the paediatric classifications of MG?
o Neonatal – Born to a myasthenic mother. Disease is self-limiting (in 6 weeks approx.)
o Congenital – Infants born to non-myasthenic mothers.
o Juvenile – Develops between infancy and puberty. More spontaneous remissions than adults, slower progress.
What are the adult classification of MG?
o Ocular – Limited to the eye muscles.
o Generalised – Fatigability of striated muscle: bulbar, limbs, facial, respiratory.
What are the causes of MG?
- Enlarged/tumourous thymus gland (in the chest) – Thymus gland is involved in developing the immune system in childhood, specifically T cells, it then should shrink in adulthood however in many cases of MG it remains large.
- Associations:
o Thyroid dysfunction
o More common in other auto immune conditions such as lupus or rheumatoid arthritis.
What are the signs and symptoms of MG?
- General
o Fatigue
o Lack of energy - Bulbar
o Problems with speech - Limb girdle
o Difficulty getting out of a chair
o Difficulty climbing stairs - Respiratory
o Problems breathing - Facial
o Lack of facial expression
What are the ocular signs and symptoms of MG?
- Ptosis
o Variable, fatigable, often bilateral but can be asymmetrical - Diplopia
o Can mimic multiple conditions including nerve palsies, gaze palsies and INO
What do we want to ask in the history if we suspect MG?
o Ask about variability and changes throughout the day
o Any activities that make symptoms worse (ie exercise or heat)
o Generalised symptoms (problems chewing, raising arms, movement)
o General health conditions (other autoimmune conditions, diabetes, thyroid problems.
What might we see on OM in patients with MG?
o Variability during the exam and between visits
May mimic nerve palsies or restrictions, subtle or marked problems.
Hess chart can be used to plot changes over visits (as can fields of BSV or fields of uniocular fixation)
May vary or increase during assessment but can take more than one visit to see variability in symptoms.
o Increase in limitations on sustained gaze
o Normal saccades but fatigue quickly
What are the names of specific tests designed to check for MG?
Enhanced ptosis (gorelicks sign)
Cogans lid twitch
Sustained elevation
Peek sign
Ice pack test
What are the names of specific tests designed to check for MG?
Enhanced ptosis (gorelicks sign)
Cogans lid twitch
Sustained elevation
Peek sign
Ice pack test
How is enhanced ptosis/Gorelicks sign tested?
Lift more ptotic lid and in MG, the other side increases due to Herrings law of equal innervation
How is cogans lid twitch tested?
Patient looks down for 15s then makes quick refixation to PP, ptotic lid moves above the previous position before returning to its ptotic position
How is sustained elevation (Simpsons test) assessed?
Patient elevates their eyes for 2 mins, lids slowly fatigue or patient has trouble maintaining fix’n.
How is peek sign assessed?
Patient cannot bury lashes or prevent eyes being opened with slight pressure. Orbicularis weakness.
How is the ice pack test performed?
Ice pack held against ptotic eye for 2 mins. Ptosis should be noted to improve by >2mm. Diplopia may also improve. This method works due to the biochemical basis principle of low temperatures enhancing neuromuscular transmission.
