The clinical and electrophysiological data of 18 consecutive adult patients with 
paraneoplastic Lambert-Eaton myasthenic syndrome (LMES) have been reviewed. The 
cancer associated with LEMS was small-cell lung carcinoma (SCLC) in 15 cases and 
epidermoid lung carcinoma in 3 cases. The main clinical neurological features 
were proximal lower limb weakness (100%), depressed tendon reflexes (94%) and 
dryness of the mouth (66%). The results of repetitive nerve stimulation (RNS) 
were not statistically different in the paraneoplastic LEMS group and in a group 
of 6 LMS patients in whom no carcinoma had been detected. Low-amplitude compound 
muscle action potential (CMAP) was present in all cases; decremental response at 
low stimulation rates was present in 13/15 cases. An abnormal incremental 
response at high stimulation rates was observed in all cases. A close 
correlation between CMAP amplitude and clinical condition was found in 4 cases 
during the long-term follow-up. In one patient the RNS electrical pattern could 
be misinterpreted as myasthenia gravis in only one muscle tested. We underline 
the usefulness of a 50 Hz stimulation during 4 seconds to establish the 
diagnosis unequivocally, and that of post-exercise facilitation in routine 
detection among an SCLC population. Our results suggest that CAMP amplitude and 
RNS test could be used to evaluate the short-term improvement of LMS under 
treatment and, in some cases, for the long-term follow-up. The infraclinical 
axonal neuropathy detected in 8 patients probably was another associated 
autoimmune paraneoplastic complication.