Examine face, CNs eyes
Approach to Ptosis (See Ptosis) and weakness
Ptosis with fatigability
Variable strabismus and diplopia that occurs after some time
Check for hyperthyroid and thyroid eye disease
Check for anaemia
Check for malar rash of SLE
VII – show your teeth : snarls
Assessment of speech : Yeeee or count 1 to 20, nasal voice (bulbar palsy)
Masseter weakness but pterygoids normal
Check neck for goitre and scars
Normal deep tendon reflexes (Eaton Lambert and Miller Fisher are reduced)
Fatigability with weakness
RA and SLE features
Thymectomy scar and plasmapheresis line
Endo: Thyroid, DM, Pernicious anaemia
CTD: RA, SLE, Polymyositis
D-penicillamine usage for RA or Wilson’s
Antibiotics and CVS drugs that can worsen MG
Temperature chart for fever – precipitate weakness
Sir, this patient has myasthenia gravis as evidenced by presence of muscle weakness
with fatigability. The patient’s deep tendon reflexes and sensation are normal.
On examination of the face, there is presence of bilateral facial muscle weakness
producing a mask-like facies with ptosis. I noticed furrowing of her forehead
musculature in an attempt to compensate for the ptosis. There is presence of variable
strabismus and diplopia after sustained gaze. I also noticed the presence of a nasal
voice as well as a reduction in volume of his speech when asked to count from 1 to
20. The patient does not require a nasogastric tube.
I did notice mid line sternotomy scar which suggest previous thymectomy.
There is no goitre or features of hyperthyroidism. Patient also does not have
symmetrical deforming polyarthropathy to suggest RA and has no cutaneous features
of SLE. I also did not notice any diabetic dermopathy.
I would like to complete my examination by
Checking his negative inspiratory force
In summary, this patient has myasthenia gravis with mild weakness of which a
thymectomy has been done previously.
What is Myasthenia Gravis?
Autoimmune condition with antibodies targeting the post-synaptic Ach receptors
of the neuromuscular junction
Resulting in progressive muscle weakness with use of the muscle and recovery of
strength after a period of rest
Weakness experienced once number of receptors is 30% or less
How common is the thymus involved?
75% of cases of which 15% are thymomas and 85% are thymic hyperplasia
What are the common presentations?
20 to 30 years old with female predominance
>50 years old with male predominance
Dysarthria, difficulty swallowing (isolated bulbar muscles involvement occurs in
Generalised weakness or reduced exercise tolerance
Respiratory failure in 1%
Tends to occur extraocular muscles first, then to facial to bulbar and to limbs and
What can exacerbate MG or precipitate crisis?
Non compliance to medications
Antibiotics: aminoglycosides, tetracyclines, macrolides and fluoroquinolones
CVS : Beta blockers, Calcium channel blockers (verapamil)
Others : Chloroquine, quinidine, procainamide, Li, Mg, Prednisolone,
quinine(in gin tonic drinks), penicillamine
What is cholinergic crisis?
Can cause confusion between myasthenic crisis from cholinergic crisis
Results from excess of cholinesterase inhibitors such as neostigmine and
Causes flaccid paralysis and SLUDGE (Miosis, salivation, lacrimation, urinary
incontinence, diarrhea, gastrointestinal hypermotility and emesis)
How would you investigate?
Positive in 80% with generalised MG
Positive in only 50% with ocular involvement only
also present in 90% of patients with penicillamine induced MG
Antistriated musce Ab
Anti Muscle specific kinase Ab (Anti MuSK Ab – positive in patients with
AchR Ab –ve)
FBC to rule out infection
CXR – thymus (anterior mediastinal mass), aspiration pneumonia
CT for thymus
Dx and distinguishing from cholinergic crisis
Edrophonium (T1/2 10 mins)
Look for objective improvement in ptosis (require observer)
Cardiac monitoring for bradycardia and asystole (Rx with atropine)
1 mg test dose and up to 10 mg
In cholinergic crisis, will get increased salivation etc
Note that in ALS, improvement in muscle weakness also occurs
Ice Pack test
Ice applied with glove to eyelids for 2 mins
Improvement in ptosis is dx (positive in 80%)
Repetitive nerve stimulation test – shows a decrease in the compound muscle
action potential by 10% in the 4th
response to a train of nerve stimuli
Single fibre nerve electromyography – evidence of neuromuscular blockade
with increased jitter
How do you grade the severity of the weakness?
Myasthenia Gravis Foundation of America
o Grade 1 – affects the ocular muscles only
o Grade 2 – mild weakness affecting muscles other than ocular muscles
2A – Affects the limb and axial muscles
2B - Affects the respiratory and bulbar muscles
o Grade 3 – moderate weakness (3A AND 3B)
o Grade 4 – Severe weakness (4A and 4B)
o Grade 5 – Intubation required
o I: Ocular
o II A: Mild generalised with slow progression
o II B: Moderate generalised
o III: Acute fulminant MG
o IV: late severe MG (takes 2 yrs to progress from I to II)
How would you manage?
Emergencies in crisis (ABC)
Treat exacerbating factors
Stop medications that can exacerbate
Treat fever with antipyretics
Oral pyridostigmine, neostigmine
Steroids, azathioprine, cyclosporine
What are the complications?
Severe exacerbation of MG
10% require intubation
Cx of medications
What is Eaton-Lambert syndrome?
Myasthenic disorder associated with malignancy such as small cell ca of lung
Affects the proximal (especially the pelvic girdle and thigh) and truncal
musculature; bulbar muscles is rarely involved
Improves with exercise
Presence of Abs to calcium channels