Further insight on A-wave in acute and chronic demyelinating neuropathies.

A-wave is a late motor response that maintains the same characteristics of latency, amplitude and shape with every electrical stimuli at a proper given intensity. The presence of A-waves was reported both in chronic (CIDP) and acute (AIDP) forms of inflammatory demyelinating polyradiculoneuropathy. It is attributed to the effect of either sprouting phenomena or ephaptic/ectopic discharge. In the first condition it could be a sign of functional recovery, while in the second it could represent an early indicator of demyelination. Aims of our research were to investigate retrospectively the presence of the A-waves, establishing whether its frequency is more common in CIDP or AIDP. Data from 77 patients, 57 male and 20 female, mean age 60.7 years (SD 15.4), were recovered from clinical records and their neurophysiological tests retrieved for reanalysis. Our results seem to indicate that A-waves can represent an early sign of acute pathology of peripheral nervous system.