Cancellation of single F wave by double stimulation in case of chronic denervation.

Single F waves evoked by stimulation with above threshold intensity are cancelled by a second shock, as was previously demonstrated with maximal or sub-maximal intensity. Double stimulation of any intensity thus makes it possible to detect a possible reflex component in the spinal response, by elimination of the F wave. As an H or a heteronymous H reflex may be a sign of a disordered central motor system state, this fast method has a direct clinical utility.