INTRODUCTION Two previously reported Norwegian patients with painful muscle cramps and giant myotonic discharges were genotyped and compared with those of members of 21 families harboring the same mutation. METHODS Using primers specific for SCN4A and CLCN1, the DNA of the Norwegian family members was amplified and bidirectionally sequenced. Clinical and neurophysiological features of other f...

A 48-year-old man presented with episodic paraplegia and stiffness of hands, face, and tongue, along with eyelid myotonia when exposed to cold temperature, which he had since childhood. Eyelid myotonia was evoked either by exposure to cold weather (video on the Neurology® Web site at www.neurology.org and figure 1) or by forceful eye closure. Myotonia was elicited with percussion of the tongue ...

Paramyotonia congenita, the major characteristics of which are cold-induced and exercise-induced myotonia, is an autosomal-dominant muscle disease which is classified into one of a group of muscle diseases, so-called muscle "sodium channelopathies" caused by missense mutations in the gene coding for the skeletal muscle sodium channel a-subunit (SCN4A) (1-4). Such muscle sodium channelopathies s...

Toxic thyroid adenoma presenting as hypokalemic periodic paralysis is extraordinarily rare. We describe a 26-year-old Japanese man who suffered from acute and painful muscle weakness of extremity in the morning. Physical examination showed a left anterior neck mass and laboratory tests revealed hypokalemia during his paralysis, and thyrotoxicosis. Neck sonogram showed a solitary nodule in the l...