1.4 Myasthenia Gravis II Flashcards
What kind of condition is Myasthenia Gravis?
Autoimmune condition, a potentially life-threatening condition.
What are the three paediatric versions of myasthenia gravis?
Neonatal – Born to a myasthenic mother. Disease is self-limiting (in 6 weeks approx.)
Congenital – Infants born to non-myasthenic mothers.
Juvenile – Develops between infancy and puberty. More spontaneous remissions than adults, slower progress.
What are the two adult versions of myasthenia gravis?
Ocular – Limited to the eye muscles.
Generalised – Fatigability of striated muscle: bulbar, limbs, facial, respiratory.
(Drug related)
What are the causes of myasthenia gravis?
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.
What can be associations of myasthenia gravis
Thyroid dysfunction
More common in other auto immune conditions such as lupus or rheumatoid arthritis.
What are the general signs and symptoms of generalised myasthenia gravis?
Fatigue
Lack of energy
What are the bulbar signs/symptoms in generalised myasthenia gravis?
Problems with speech
What are the limb girdle signs/symptoms in generalised myasthenia gravis?
Difficulty getting out of a chair
Difficulty climbing stairs
What are the respiratory signs/symptoms in generalised myasthenia gravis?
Problems breathing
What are the facial signs/symptoms in generalised myasthenia gravis?
Lack of facial expression
What are the ocular signs/symptoms of myasthenia gravis?
Ptosis - Variable, fatigable, often bilateral but can be asymmetrical
Diplopia - Can mimic multiple conditions including nerve palsies, gaze palsies and INO
What are key points to note in history taking with myasthenia gravis?
Ask about variability and changes throughout the day
Any activities that make symptoms worse (ie exercise or heat)
Generalised symptoms (problems chewing, raising arms, movement)
General health conditions (other autoimmune conditions, diabetes, thyroid problems.
What are the key observations to note in myasthenia gravis?
Frontalis overaction (use of brow to raise lids)
What are key ocular movements to note in myasthenia gravis?
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.
Increase in limitations on sustained gaze
Normal saccades but fatigue quickly
What are the clinical tests that can be done to identify myasthenia gravis?
Enhanced ptosis (Gorelick’s sign)
Cogans lid twitch
Sustained elevation (Simpson’s test)
Peek sign
Ice pack test
Breifly explain the enhanced ptosis (Gorelick’s sign) method.
Lift more ptotic lid and other side increases due to Herrings law of equal innervation.
Briefly explain the Cogans lid twitch method.
Patient looks down for 15s then makes quick refixation to PP, ptotic lid moves above previous position before returning to ptotic position.
Briefly explain the sustained elevation (Simpson’s test) method.
Patient elevates eyes for 2 minutes, lids slowly fatigue, or patient has difficulties maintaining fixation.
Briefly explain the peek sign method.
Patient can’t bury lashes or prevent eyes being opened with slight pressure. Orbicularis weakness.
Briefly explain the ice pack test method.
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.
What are some further investigations that can be done to diagnose myasthenia gravis?
Bloods - Acetylcholine or MuSK antibodies.
Thymus imaging - looking for enlargement.
Single fibre EMGs
What are some medical treatments for myasthenia gravis?
Thymectomy - the removal of the thymus gland surgically
Pyridostigmine (anti-acetylcholinesterase)
Cortico-steroids (prednisolone)
What are some orthoptic treatments for myasthenia gravis?
Prisms – often not helpful due to variability
Occlusion – foil/patch
Ptosis props – uncomfortable
Patient information – charities
