neuromuscular junction disease Flashcards
what is myasthenia gravis and its pathophysiology?
autoimmune condition
production of antibodies against nicotinic receptors at NMJ
what antibodies are associated with myasthenia gravis?
anti-AchR
anti-MuSK
what are the main symptoms of myasthenia gravis?
muscle weakness and fatigability
what conditions are associated with myasthenia gravis?
disease of the thymus
SLE
rheumatoid
what makes the weakness in MG worse?
pregnancy
emotion
exercise
drugs
what drugs make MG worse?
B blockers
opiates
gentamicin
tetracyclines
who is MG most common in?
females
peaks at early 30s in females and peak in men in 60/70s
what is the typical presentation of weakness in MG?
fluctuating and fatiguing muscle weakness
weakness getting worse throughout the day and with repeated use of the muscle
what order of muscle weakness do muscles tend to be affected in in MG?
extra ocular - double vision, ptosis bulbar - dysphagia, dysarthria facial - dropping, snarled expression with smiling neck limb girdles trunk - difficulty breathing laryngeal muscles - quieting of voice
what is seen on examination in MG?
normal sensation and reflexes
normal muscle appearance and tone
snarled appearance with ptosis
peek sign - sclera will show when patient’s close eyes
what is the tensilon test?
give edrophonium - acetylcholinesterase inhibitor
improve symptoms in seconds
what is the management of MG?
pyrostigmine - anti cholinesterase
thymus abnormality - thymectomy
relapses - immunosuppression (prednisolone)
what is myasthenia crisis?
severe relapse resulting in weakness of respiratory muscles and difficulty breathing
how do you manage myasthenia crisis?
ventilatory support
IV Ig or plasmapheresis
what is lambert eaton myasthenia syndrome?
disease of pre-synaptic calcium channels
reduced function of channels limits amount of Ach released from presynaptic terminals
what can cause Lambert eaton myasthenia syndrome?
autoimmune
paraneoplastic syndromes - small cell lung cancer
what it the presentation of LEMS?
muscle weakness
how is LEMS different to MG?
improvement with exercise
primarily limb symptoms leading to gait disturbance
ocular muscle symptoms occurring laterally
hyporeflexia with improvement of reflexes on exercise
how is LEMS diagnosed?
low frequency muscle action potentials
what other investigations should be done for LEMS?
CT CAP to screen for malignancy
what is the management for LEMS?
3,4 diaminopyradine
what is botulism?
infection with clostridium botulinum
what is botulism associated with?
IVDU and penetrative wounds
how does botulism present?
afebrile
flaccid paralysis
how is botulism managed?
anti toxin
