Lambert-Eaton Myasthetic Syndrome (LEMS) Flashcards
LEMS can be paraneoplastic or …
Autoimmune
What type of cancer is LEMS most often seen in associate with?
Small cell lung cancer
Lesser extent: breast and ovarian
It is caused by an antibody direct against..
Presynaptic voltage gated calcium channels in peripheral nervous system
What features are associated?
Repeated muscle contractions lead to increased muscle strength (in reality, following prolonged muscle use, muscle strength eventually decreases)
Limb girdle weakness - lower limbs affected first
Hyporeflexia and weakness that improves after exercise
Autonomic involvement
Extraocular and respiratory muscle involvement are RARE
What autonomic symptoms are seen?
Dry mouth Difficulty micturating Impotence Constipation Sweating Blurred vision Orthostic hypotension
Is ptosis and opthalmoplegia a common feature?
No - unlike in myasthenia gravis
What can be seen on EMG?
Incremental response (amplitude increases) post exercise
How is LEMS managed?
Immunosuppression e.g prednisolone
3,4 diaminopyridine - blocks K channel efflux in nerve terminal so actionable potential duration increased - calcium channels can open for longer (allow greater ACh release)
IV immunoglobulin and plasma exchange
Regular CXR / CT as symptoms may precede cancer by 4 years
What does a paraneoplastic syndrome mean?
A condition that arises as a result of cancer elsewhere in the body
Does the weakness affect the legs or arms more?
Legs - difficulty climbing stairs and rising from sitting position
Is weakness of the eye muscles common?
No
What is Lambert’s sign?
Strength improves with repeated testing e.g improvement of power on repeated hand grip
At rest reflexes are typically reduced, with muscle use reflexes typically…
Increases
