Trigeminal evoked potentials in man: a new olfactory stimulation device

The recording of olfactory evoked potentials in healthy humans, using a continuous flow olfactory stimulator, is described. A stimulator pushed inert gas (N2) in a continuous flow through the nose at a rate of 4 l/min. At fixed 30-second intervals, (32 times) the flow was replaced by an equal amount of CO2, a trigeminal stimulant. Each pulse lasted 200 ms. An electronic timing circuit triggered both the stimulator and the recorder. Signal acquisition was performed using an Evoked Potential Recorder (Nicolet Compact Four by Nicolet Biomedical Instruments), triggered by the stimulator. Using this stimulator device reliable olfactory evoked potentials can be recorded in a clinical setting. Since this is a non invasive technique which can be used to test olfactory function whether or not the patient cooperates, it is expected to become widely used, particularly in non collaborating patients and in those suspected of malingering.