Painful Diabetic Neuropathy - A Therapeutic Challenge For The New Millennium

Clinical spectrum of diabetic neuropathy is variable; it may be asymptomatic, but once established, it becomes irreversible and disabling. Some investigators suggested that earliest change in diabetic nerve function is alteration in axonal excitability due to alterations in ion conductance of axon membrane, although these functional changes of ion channels necessarily cause permanent damage or degeneration of nerve fibers. Among various parameter of nerve conduction study in diabetics, prolonged F-wave latency in the peroneal and tibial nerve seems the commonest abnormality in asymptomatic patients. Decrease in amplitude of compound sensory action potential of sural nerve is another earlier abnormality, which is, then, accompanied by a fall in motor amplitude of peroneal and tibial nerves in advanced patients. In disabled patients no motor response is often elicited in the legs. Previous electrophysiological studies could not make clear if central axons were involved or not in diabetic neuropathy. Recently, our group has demonstrated that somatosensory central conduction from the spinal cord to the sensory cortex is delayed in diabetics as well as in the peripheral conduction, which might be partly responsible for the irreversible clinical presentation of diabetic neuropathy.