Lambert-Eaton myasthenic syndrome (LEMS) prognosis is determined by the presence and type of underlying cancer, the presence and severity of associated autoimmune disease, and the severity and distribution of weakness.
In association with cancer (CA-LEMS)
Long-term prognosis is determined by the prognosis and recurrence rate of the underlying cancer. Small cell lung cancer (SCLC) has a better prognosis when associated with LEMS (one study reported 15- to 17-month survival in patients with SCLC and CA-LEMS, compared with 9- to 10-month survival in patients without CA-LEMS); this may be due to earlier tumour detection.[7]Titulaer MJ, Verschuuren JJ. Lambert-Eaton myasthenic syndrome: tumor versus nontumor forms. Ann N Y Acad Sci. 2008;1132:129-34.
http://www.ncbi.nlm.nih.gov/pubmed/18567862?tool=bestpractice.com
[50]Maddison P, Newsom-Davis J, Mills KR, et al. Favourable prognosis in Lambert-Eaton myasthenic syndrome and small-cell lung carcinoma. Lancet. 1999 Jan 9;353(9147):117-8.[51]Liu Y, Xi J, Zhou L, et al. Clinical characteristics and long term follow-up of Lambert-Eaton myasthenia syndrome in patients with and without small cell lung cancer. J Clin Neurosci. 2019 Jul;65:41-5.
http://www.ncbi.nlm.nih.gov/pubmed/31072737?tool=bestpractice.com
[52]Lipka AF, Boldingh MI, van Zwet EW, et al. Long-term follow-up, quality of life, and survival of patients with Lambert-Eaton myasthenic syndrome. Neurology. 2020 Feb 4;94(5):e511-20.
https://www.neurology.org/doi/10.1212/WNL.0000000000008747
http://www.ncbi.nlm.nih.gov/pubmed/31831596?tool=bestpractice.com
Weakness typically improves with effective cancer treatment.[53]Chalk CH, Murray NM, Newsom-Davis J, et al. Response of the Lambert-Eaton myasthenic syndrome to treatment of associated small-cell lung carcinoma. Neurology. 1990 Oct;40(10):1552-6.
http://www.ncbi.nlm.nih.gov/pubmed/2170866?tool=bestpractice.com
Not associated with cancer but as part of more general autoimmune state (NCA-LEMS)
Initial degree of proximal muscle strength has been shown to correlate with long-term outcome, although neither electrophysiological findings nor anti-voltage-gated calcium-channel antibody levels correlate.[44]Maddison P, Lang B, Mills K, et al. Long term outcome in Lambert-Eaton myasthenic syndrome without lung cancer. J Neurol Neurosurg Psychiatry. 2001 Feb;70(2):212-7.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1737207/pdf/v070p00212.pdf
http://www.ncbi.nlm.nih.gov/pubmed/11160470?tool=bestpractice.com
Up to half of patients may achieve sustained clinical remission with substantial doses of immunosuppressive medications.[44]Maddison P, Lang B, Mills K, et al. Long term outcome in Lambert-Eaton myasthenic syndrome without lung cancer. J Neurol Neurosurg Psychiatry. 2001 Feb;70(2):212-7.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1737207/pdf/v070p00212.pdf
http://www.ncbi.nlm.nih.gov/pubmed/11160470?tool=bestpractice.com
Most will continue to have long-term disability despite therapeutic measures. NCA-LEMS does not seem to reduce life expectancy.[52]Lipka AF, Boldingh MI, van Zwet EW, et al. Long-term follow-up, quality of life, and survival of patients with Lambert-Eaton myasthenic syndrome. Neurology. 2020 Feb 4;94(5):e511-20.
https://www.neurology.org/doi/10.1212/WNL.0000000000008747
http://www.ncbi.nlm.nih.gov/pubmed/31831596?tool=bestpractice.com