Lambert-Eaton Syndrome Flashcards
What is Lambert-Easton Myasthenic Syndrome
Autoimmune disorder involving NMJ causing muscle weakness
What is LEMS often associated with
paraneoplastic syndrome; Small cell lung cancer!
What are RF for LEMS
Malignancy
Personal or FHx of autoimmune disorder (T1DM, Hashimotos, Grave’s disease)
What is an essential step in normal NMJ patho
Influx of calcium triggers release of Ach to cause a contraction
What happens to NMJ pathophys in LEMS
Antibodies bind to voltage gated calcium channels, interfere with Ca influx, reduce Ach release, and impair muscle function
What is the pathophys behind Paraneoplastic LEMS
Antibodies develop due to VGCC on the surface of the malignancy (SCLC)
What is the pathophys behind non-paraneoplastic LEMS
Trigger for developing the VGCC antibodies is unknown
What is the clinical manifestation of LEMS
slowly progressive symmetric proximal limb/muscle weakness (more rapid and impaired in Paraneoplastic)
-Altered gait (hard to get out of chair or do stairs)
Depressed or absent DTR
Muscle fatigue and cramping after prolonged exercise
What finding is unique to LEMS
Recovery of DTR/ improved muscle strength with brief vigorous muscle activation (post-exercise facilitation)
What autonomic dysfunction occurs in LEMS
*Dry mouth (reduced salivation)
Slow pupil light response
ptosis, diplopia, dysphagia, impotence, orthostatic hypotension
What diagnostic studies can be done to diagnose LEMS
Nerve conduction study (NCS) and EMG (show reduced baseline amp- repeat nerve stim shows increased amplitude)
VGCC antibodies
+/- malignancy work up (CXR, CT)
What are some Ddx for LEMS
GBS- but it’s painful
MG- but it has post-workout fatigue
ALS- but it’s unilateral
Inflammatory muscle disease
How do you treat LEMS
-Tumor resection ( if paraneoplastic)
-Monitor if mild weakness w/o sig. impairment
-Mod-sev weakness: Pyridostigmine (ACh-ase inhibitor) -or- 3,4DAP (increase Ca entry)
-Prednisone and azathioprine (immunosuppression)
IVIG
