NMJ Dysfunction Flashcards
What is myasthenia gravis
Autoimmune destruction of nicotinic ACh receptors on postsynaptic membrane at neuromuscular junction I.e on skeletal muscle
Symptoms of myasthenia gravis
Fatiguable!!! Ptosis Diplopia Strabismus Proximal muscle weakness Dysphagia Facial muscle weakness NORMAL REFLEXES
Investigations for myasthenia gravis
Anti-AChR antibodies
Anti-MuSK antibodies
EMG
CT thorax
What is myasthenia gravis associated with
Thymoma
Penicillamine
RA
Management of myasthenia gravis
Acute management - IV Ig, plasmapheresis, corticosteroids
Acetylcholinesterase inhibitors - pyridostigmine
Thymectomy
+/- ventilation
Describe myasthenic crisis and management
Under treatment leading to type 2 respiratory failure
Mx: ventilation, IV Ig, plasmapheresis
Don’t give acetylcholinesterase inhibitors as they increase respiratory secretions
Describe cholinergic crisis and management
Over treatment with acetylcholinesterase inhibitors leading to respiratory muscle spasms
Mx: atropine, ventilation
What is LEMS
Lambert-Eaton myasthenia syndrome
Paraneoplastic syndrome associated with small cell lung cancer where there is autoimmune destruction of voltage gated calcium channels leading to impaired ACh release from presynaptic LMN
Clinical features of LEMS
Symptoms improve with activity!!! Proximal muscle weakness Hyporeflexia Ptosis Diplopia Autonomic symptoms (postural hypotension, erectile dysfunction)
Investigations for LEMS
Anti-AChR Anti-MuSK Anti-VGCC EMG CXR
Management of LEMS
IV Ig
Plasmapheresis
Corticosteroids
Pyridostigmine has minimal benefit
