Vibrator
The use
of penile vibratory stimulation (PVS) to induce penile erection and ejaculation
was first described by Sobrero and colleagues in 1965 in men without spinal
cord injury (SCI) [Sobrero et al. 1965; Sonksen and Ohl, 2002]. The
first reported use of PVS in a man with SCI was with a hand device in 1970
[Sonksen and Ohl, 2002]. Refinements in technique, advancements in technology
and portability led to the first US Food and Drug Administration (FDA) approved
penile vibratory stimulator for ED in July 2011.
Viberect, developed by Reflexonic, Chambersburg, Pennsylvania,
is an FDA approved class II medical device used to provoke penile erection in
men with ED and to provoke ejaculation in men with SCI (Figures 3 and 4).
Figure 3: Viberect device. The blue circular pads are placed in contact with
the penile shaft and using a touch pad on the dorsal aspect of the device the
individual is able to customize activation. Source: www.reflexonic.com
The device has received an abundance of online and commercial
press. The mechanism of action of the device is through vibratory stimulation
to branches of the pudendal nerve along the penile shaft.
Penile erection
requires a complex interplay of the central nervous system, local and
endothelial mediators. Sexual stimulation causes a release of neurotransmitters
from the cavernous nerve terminals. Specifically, stimulation of the pudendal
nerve causes a reflex parasympathetic erection through an activation of the
parasympathetic pathway by pelvic nerves and nonadrenergic noncholinergic
(NANC) fibers [Everaert et al. 2010].
Nitric oxide (NO) is the neurotransmitter released by NANC fibers. NANC fibers
play a pivotal role in achieving tumescence after central nervous system
stimulation by way of facilitating the release of NO and vasoactive intestinal
polypeptide (VIP) and inhibiting noradrenaline release from the sympathetic
fibers. The cumulative and downstream effect is a dilation of cavernosal and
spongiosal smooth muscle through the activation of intracellular second
messengers such as cyclic guanosine monophosphate (cGMP) and cyclic adenosine
monophosphate (cAMP). The Viberect handheld device utilizes exogenous
stimulation of cavernousal nerve fibers by way of vibratory frequencies to
release NO from nerve terminal endings [Tajkarimi and Burnett, 2011]. It may
serve as an option for penile rehabilitation after nerve sparing radical
prostatectomy. However, well designed clinical trials are needed to evaluate
its efficacy.
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