BACKGROUND: Neuromuscular symptoms in patients with Lambert-Eaton myasthenic 
syndrome (LEMS) and a small cell lung cancer (SCLC) develop more rapidly than in 
LEMS patients without a SCLC. We studied how this clinical information, which is 
readily available at the first consultation, can be used to predict the presence 
of SCLC.
PATIENTS AND METHODS: In our study we included 52 LEMS patients with SCLC and 45 
non-tumor patients (NT-LEMS). We interviewed patients using a structured 
checklist and reviewed their clinical records. We compared frequency and onset 
of symptoms during the course of LEMS.
RESULTS: In the first six months, over half the SCLC-LEMS patients had developed 
seven separate symptoms, while NT-LEMS patients developed only two symptoms. 
Proximal leg weakness and dry mouth were early symptoms in both groups. Rapid 
involvement of proximal arm muscles (p=0.0001), distal arm muscles (p=0.0037), 
distal leg muscles (p=0.0002), dysartria (p=0.0091) and the presence of erectile 
dysfunction (p=0.007) were found significantly more often in SCLC-LEMS patients 
in both cohorts. Cerebellar symptoms, although present in 9% of LEMS patients, 
were almost exclusively related to SCLC-LEMS.
CONCLUSION: A rapidly progressive course of disease from onset in LEMS patients 
should raise a high suspicion of SCLC. Special attention should be paid to 
involvement of upper extremities, involvement of distal arm and distal leg 
muscles, to erectile dysfunction and probably ataxia in order to discriminate 
between SCLC-LEMS and NT-LEMS.