[Erectile dysfunction--value of neurophysiologic diagnostic procedures].

Neurogenic, particularly autonomic disorders, frequently contribute to the etiology and pathophysiology of erectile dysfunction. Parasympathetic and sympathetic outflow mediates erection. Noncholinergic, nonadrenergic neurotransmitters induce activation of cyclic monophosphates, leading to relaxation of smooth muscles of the corpora cavernosa and by this to tumescence and rigidity, i.e. erection. The diagnosis of neurologic causes of erectile dysfunction requires a detailed history and neurologic examination. Conventional neurophysiological procedures evaluate the function of rapidly conducting, thickly myelinated nerve fibers only. Therefore, techniques such as sphincter ani externus electromyography, latency measurements of the pudendal nerve or bulbocavernosus reflex studies frequently do not contribute to the diagnostic process. The evaluation of small nerve fibers that are essential for erection, for example by means of psychophysical quantitative thermotesting, might improve the diagnosis of neurogenic causes of erectile dysfunction. In addition, the assessment of heart rate variability at rest, during metronomic breathing, Valsalva maneuver, and active standing might be helpful to identify an autonomic neuropathy as the cause of erectile dysfunction.