Lambert-Eaton Myasthenic Syndrome Medical Slides

Create a comparison table: LEMS (proximal weakness improving with repetition, hyporeflexia that normalizes after exercise, autonomic dysfunction prominent — dry mouth, constipation, erectile dysfunction, presynaptic VGCC antibodies) vs MG (fatigable weakness worsening with repetition, normal reflexes, no autonomic features, postsynaptic AChR antibodies). On NCS: LEMS shows low initial CMAP with >100% increment at high-frequency stimulation, while MG shows >10% decrement without increment.

Present the DELTA-P score (Dutch-English LEMS Tumour Association Prediction) to stratify cancer risk: bulbar involvement, weight loss, smoking history, Karnofsky score, male sex, age >50, and SOX1 antibody positivity. High-risk patients require CT chest ± PET-CT at diagnosis and every 6 months for 2 years. Emphasize that cancer typically manifests within 2 years of LEMS diagnosis, and that paraneoplastic LEMS may improve with cancer treatment.

Present 3,4-diaminopyridine (amifampridine) as the first-line symptomatic treatment: blocks presynaptic potassium channels, prolonging the action potential and increasing calcium influx and acetylcholine release. Dosing starts at 15-30 mg/day divided TID-QID, titrating to 60-80 mg/day maximum. FDA-approved as Firdapse in 2018. Emphasize that for paraneoplastic LEMS, treatment of the underlying cancer is the most effective therapy, combined with immunosuppression (IVIG, prednisone, azathioprine).