The nature of the electrophysiological disorder in adynamia episodica.

In 1934 Biemond and Daniels first showed that the serum potassium level fell during paralytic episodes in patients with familial periodic paralysis. Subsequently a normokalaemic form of the disease was recognized (1951), while more recently a hyperkalaemic variety was described by Helweg-Larsen, Hauge, and Sagild (1955). This last type of periodic paralysis was given the name adynamia episodica hereditaria by Gam-storp (1956). In view of the functional relationship between electrical potential and potassium conductance across cell membranes (Hodgkin, 1958), it has been widely anticipated that intracellular recording from muscle fibres in these various conditions might prove a valuable analytical approach. Up to the present time such studies have been carried out on patients with hypokalaemic familial periodic paralysis by while the last authors have also investigated a single patient with the hyperkalaemic variety. Recently we have had an opportunity to make intracellular recordings, between attacks, in a further four patients with hyperkalaemic paralysis and in one with the normokalaemic syndrome. The results to be described indicate that the hyper-and normokalaemic varieties appear to be functionally similar in so far as the resting membrane potential is reduced in both. In addition we have employed intracellular stimulation to investigate the electrical properties of the fibre membranes more fully; the results obtained have been considered in relation to the genesis of the paralytic episodes.