[Nocturnal erectile activity in erectile dysfunction. An examination of nocturnal penile tumescence and rigidity].Ugeskr Laeger. 1989 Jan 09; 151(2):81-3.UL
The historical background for the use of sleep-related erections (nocturnal penile tumescence) to distinguish organogenic from psychogenic impotence is reviewed. A commercially available system for continuous, non-invasive measurement of penile tumescence and rigidity is presented.