Objectives-To determine the prognosis in patients with Lambert-Eaton myasth
enic syndrome (LEMS) without small cell lung cancer (SCLC), and to analyse
longitudinal clinical, electrophysiological, and immunological data on each
patient to establish prognostic factors for long term outcome.
Methods-The retrospective and part prospective study of 47 patients with LE
MS was undertaken from data recorded during visits to a specialist neuromus
cular clinic. Serial measurements of muscle strength score in shoulder abdu
ction, elbow extension and hip flexion, compound muscle action potential (C
MAP) amplitude, and postcontraction increment in abductor digiti minimi (AD
M), and anti-P/Q-type voltage gated calcium channel (VGCC) antibody titre w
ere made at each visit.
Results-Muscle strength scores were improved in 88% of patients after a med
ian duration of immunosuppressive treatment of 6 years (range 1.3 to 17 yea
rs); anti-VGCC antibody titres fell in 52% after treatment; and mean restin
g CMAP amplitude improved from 2.7 mV initially to 8.8 mV after 2 years of
treatment p<0.001). Initial pretreatment anti-VGCC antibody titre did not c
orrelate significantly with either CMAP amplitude, CMAP increment, or clini
cal score: from serial measurements made during follow up, significant corr
elation between antibody titre and CMAP amplitude was seen in only two pati
ents. Sustained clinical remission was achieved by 20 (43%) of whom only fo
ur remained in remission without the need for immunosuppression. Using a Co
x proportional hazards model, the only independent predictor of sustained c
linical remission was initial pretreatment clinical score (p=0.03). Lymphom
a presented in three patients during the study.
Conclusions-The prognosis in patients with LEMS without SCLC is favourable,
although patients often need significant doses of immunosuppressive treatm
ent to remain clinically stable. Only initial clinical muscle strength meas
urements and not anti-VGCC antibody titres or electrophysiological recordin
gs are predictive of long term outcome.