Paramyotonia congenita (Eulenburg): clinical, neurophysiological and muscle biopsy observations in a Swedish family.

A Swedish family with Paramyotonia congenita (Eulenburg) (PMC) is presented. Clinical neurological examination, neurophysiological examination (n = 5) and muscle biopsy (n = 4) were performed. Different clinical features were found in various combinations in the individual family members. The clinical symptoms were: (1) cold-induced myotonia, (2) attacks of weakness, (3) persistent weakness and (4) no symptoms but other signs of muscle affection. In the patients with myotonia, the neurophysiological examination showed spontaneous myotonic discharges which were frequent at room temperature but disappeared after cooling. Furthermore, the amplitude of M. abductor digiti minimi compound action potential, during supramaximal ulnar nerve stimulation, decreased significantly after cooling. In the patients with persistent weakness there were no spontaneous myotonic discharges, but myopathic abnormalities were found in proximal muscle. In the patients with myotonia as well as in the patients with manifest muscle weakness, muscle biopsy showed a variation of muscle fibre diameters, centrally located nuclei, occasional atrophic fibers and an atrophy of type IIB muscle fibres. These findings are unspecific but have been described in PMC patients in earlier studies. An ancestor to the family, who had myotonia, lived in the same town and at the same time as Albert Eulenburg, which may suggest that this family is a part of the originally described family (1).