Clinical utility of axonal excitability testing in toxic neuropathies

Abstract

The peripheral nervous system is highly susceptible to the development of toxicity. Conventional nerve conduction studies may only identify nerve damage once significant axonal disturbance has occurred, due to the high safety factor of impulse transmission. Over the past 20 years, axonal excitability techniques have been developed to identify aberrant membrane and ion channel function in vivo. These techniques have been successfully utilized in the clinical research setting to provide insights into pathophysiology in a number of peripheral nerve disorders. Studies in patients with neurotoxic marine poisoning have provided important evidence of the role of sodium channels in determining peripheral axonal excitability, critical to the validation of axonal excitability techniques. Subsequent assessment of toxic neuropathies has demonstrated the advantages of axonal excitability techniques in sensitively identifying peripheral nerve dysfunction. Such examples include early detection of nerve damage in chemotherapy-induced peripheral neuropathy and the identification of potential changes in nerve function with immunomodulatory drugs. To further strengthen the clinical utility of axonal excitability studies, translation of these techniques into widely available clinical tools will be needed.