Intrathecal Baclofen Pump and Sacral Root Stimulation

An intrathecal baclofen pump is a device for treatment of severe spasticity. This medical device is placed under the skin during a surgery (generally under abdominal skin) and is used to deliver baclofen directly into the intrathecal space surrounding the spinal cord. Baclofen stimulates GABA-B receptros and acts as a skeletal muscle relaxant.

For sacral anterior root stimulation (SARS) implantation, a laminectomy is performed between S2-L4 to expose the sacral nerve roots of S2-S4 and possibly S5 (Worsoe et al. 2013). Anterior and posterior nerve roots are distinguished using intraoperative stimulation (Worsoe et al. 2013; Creasey et al. 2001). Then the sleeved electrodes are placed bilaterally along the S2-4 anterior roots and sutured onto the target nerves (Creasey et al. 2001). Meanwhile, the S2-5 posterior root nerves are sacrificed through a bilateral rhizotomy. This procedure enables urinary continence during stimulation, maintenance of bladder capacity, and reduces the risk of AD by abolishing the reflex arcs mediated by these nerves (Valles et al. 2009; Creasey et al. 2000). The electrode cables are then subcutaneously tunneled between the costal margin and iliac crest and connected to a subcutaneous transmitter box in the anterior abdominal wall (Creasey et al. 2001). The transmitter box and subsequently the stimulation can be activated by the patient using a wireless receiver block.

Discussion

Implantation of a Sacral Anterior Root Stimulator (Brindley et al. 1982) for bladder control usually entails rhizotomy of posterior sacral roots to improve bladder capacity and compliance and reduce reflex incontinence and possibly sphincter spasticity, but in so doing has the disadvantage in men with SCI of abolishing reflex erection, and ejaculation when present. While not the primary indication for implantation, continuous stimulation of S2 or S3 anterior roots has been shown to achieve a sustained and full erection in all of a series of 14 men with complete SCI lesions between C5 –T10 level (van der Aa et al. 1995). Vignes et al. (2001) reported that 60 percent of men with complete SCI were able to achieve an erection by continuous stimulation of S2 roots.

We found 3 studies (Lombardi et al. 2008; Lombardi et al. 2011; Sievert et al. 2010) that used Sacroneuromodulation Stimulation (SNS) in an effort to correct lower urinary tract dysfunction and that also measured sexual function. Proportions of participants in each study recovered erectile function and/or genital arousal; though more research with larger sample sizes are needed.

Concerns have been raised about the impact of intrathecal baclofen (a drug to control spasticity) on sexual function among men with SCI. Baclofen may have an effect on sexual function presumably secondary to the inhibition of visceral afferent input to the lumbosacral spinal cord (Steers et al. 1992). Jones et al. (2008) reported that although there was minimal impact on sexual function after baclofen pump implantation, there was a possible dose response between baclofen and sexual function (i.e. higher the dose to control spasticity, poorer the erection function). Four out of seven subjects noted a decrease in perceived sexual function following an increase in baclofen dosages, although some were utilizing PDE5i as well, and one subject reported a dramatic improvement in rating of sexual function with increase and later tapering in baclofen dose. Denys et al. (1998) reported similar inconsistent findings leading the authors to conclude that the effects of baclofen on sexual function seem to be transitory and reversible with withdrawal or reduction in dose. More recently, Calabro et al. (2014) found that before implantation, 55% of participants declared difficulties to achieve or maintain an erection, whereas after the pump implant 80% of the sample suffered from erectile dysfunction.

Conclusion

There is level 2 evidence (Lombardi et al. 2008) that Sacral neuromodulator stimulation can improve erectile function while simultaneously improving lower urinary tract dysfunction.

There is level 4 evidence (Denys et al. 1998; Jones et al. 2008; Calabro et al. 2014) that implantation of intrathecal baclofen pump, while effective in managing spasticity, may cause difficulties with erection and sexual function.

There is level 4 evidence (Lombardi et al. 2008) that implanting a sacral neuromodulator can improve sexual health and ability to achieve and maintain erection in men with SCI.