G. Chauplannaz et B. Bady, HEREDITARY MYASTHENIC SYNDROMES WITH LATE -ONSET - USEFULNESS OF ELECTROPHYSIOLOGIC TESTS, Revue neurologique, 150(2), 1994, pp. 142-148
A myasthenic syndrome was diagnosed in 3 female patients aged 37, 47 a
nd 56 years. The symptoms were first noticed in childhood, and at 16 a
nd 25 years. Respectively weakness and atrophy of finger extensor musc
les were present in all patients. In 2 of them scapular and cervical m
uscles were involved. Weakness was markedly increased by cold in every
patient. Similar symptoms were noted in first degree relatives in all
cases. Single nerve stimulus elicited a repetitive compound muscle ac
tion potential in hand muscles. Repetitive nerve stimulation induced a
myasthenic decrement in finger extensor muscles. SFEMG studies demons
trated increased jitter with frequent blockings. Genetic, clinical and
electrodiagnostic data were consistent with the hypothesis of the so-
called <<Slow-Channel>> myasthenic syndrome. As 2 of these patients we
re considered to have <<unknown myopathy>> the use of careful nerve st
imulation tests is advocated in such cases.