Pudendal evoked potentials, motor evoked potentials of the bulbocavernosus muscle to magnetic stimulation and bulbocavernosus reflex were recorded in 34 MS patients: responses were delayed in 26, 20 and 3 cases respectively. No relationship was found between neurophysiological abnormalities and the presence or severity of erectile dysfunction, showing that these tests have little diagnostic usefulness in MS patients with impotence. Nocturnal penile tumescence test was assessed in 14 cases: the test was normal in 10 patients, with no additional diagnostic help.

Nuclear medicine techniques may be used to test vasculogenic impotence. Dynamic radioisotope penogram with 0.3 mg sublingual nitroglycerin was performed in 50 impotent patients. The penogram index (Ip) and the time required to reach peak activity (Tp) was calculated. Ip was useful to differentiate vasculogenic and psychogenic impotence. The radioisotope penogram is a simple, less invasive and valuable screening test in the identification of vasculogenic impotence.