Chapter 4 Ion channel disorders in neuropathy

Publisher Summary Voltage gated ion channels permeable to Na + and K + are important in controlling the excitability of the axon membrane in the peripheral nerves among a rich repertoire of ion channels. The main pathomechanism of channelopathies of peripheral axons is antibody mediated and the targets are voltage gated sodium channels (VGSCs) and voltage gated potassium channels (VGKCs). The patch-clamp technique enables to directly measure the effect of these antibodies on voltage gated ion channels, by recording the current flow, through these channels. The pathophysiology of antibodies against VGSCs in acquired demyelinating neuropathy and VGKCs in acquired neuromyotonia (Isaacs' syndrome) is discussed in the chapter. Generalized, acquired neuromyotonia of unknown origin is called Isaacs' syndrome. Clinical, electromyographic, and pharmacological findings suggest that the nerve hyperexcitability mainly originates within the distal motor nerve, including the motor nerve ending. Many cases appear to have autoimmune or paraneoplastic causes. Recently there has been considerable interest in an autoimmune etiology for this disease, because of successful treatment, using plasma exchanges, and a decrease in the curare sensitivity of neuromuscular transmission in mice, injected with IgG, from these patients.