has not been any report which studied systematically the relationship between the repetitive nerve stimulation (RNS) test and severity of Lambert-Eaton myasthenic syndrome (LEMS) . We report such a study here.
Methods
This study was based on 57 RNS tests on the abductor digiti quinti (ADO muscle and 37 RNS tests on the flexor carpi ulnaris (FCU) muscle in 19 patients with LEMS. There were 11 men and 8 women. Ages ranged from 28 to 75 years. A tumor was found in 14 (74%) of the cases. Except for 1 patient with thyroid carcinoma and 1 with mediastinal germinoma, all other patients had small cell carcinoma of the lung. The diagnosis of LEMS was based on clinical features (easy fatigability, proximal leg weakness, and diminished or absent muscle stretch reflexes) and the classic triad on the RNS test [low compound muscle action potential (CMAP) amplitude, abnormal decremental response (> 7%) at low rate of stimulation (LRS), and adnormal incremental response (> 100%) at high rate of stimulation (HRS)] .3,5
The RNS test was performed in the ADQ and FCU muscles with stimulation of ulnar nerve at elbow and the data were analyzed following the previously described m e t h ~d . ~ Tests include the CMAP at rest and after 30-s exercise, the responses at the low rate (2-5/s) as well as the high rate (50,'s) of stimulation,