Abnormalities of autonomic function in the Lambert

SUMMARY Two cases of Lambert Eaton syndrome unassociated with an underlying malignancy are described. Both had mild autonomic symptoms but markedly abnormal autonomic function tests. These results are suggestive of a widespread defect in cholinergic transmission in addition to that at the skeletal neuromuscular junction. The Lambert Eaton myasthenic syndrome (LEMS) comprises proximal limb weakness and fatiguability associated with a characteristic incrementing electro-myographic response to stimulus rates above 10 Hz.1 Most frequently it is encountered in association with carcinoma (Ca-LEMS) particularly oat cell tumours of the lung in which it has a prevalence of 3%.2 Cases have also been reported in association with lympho-sarcoma,l carcinoma of the breast, colon, stomach and prostate,3 bladder,4 kidney and gall bladder.5 Approximately one third of cases are not associated with malignant disease (non Ca-LEMS).6 The under-lying physiological abnormality lies in the presynaptic membrane where there is a decrease in the number of quanta of acetylcholine released by each nerve impulse although the resting frequency of miniature end plate potentials and quantal size are unaltered.78 Symptoms possibly related to autonomic involve-ment occur in about half the patients and are usually confined to a dry mouth and, in men, impotence9 although impaired sweating'0 and constipation" have also been reported. Autonomic function tests have been formally assessed previously in four LEM