Optimizing the efficiency of electrical stimulation of peripheral nerves to restore pudendal nerve functions.

Bladder dysfunction (BD) and sexual dysfunction (SD) are severe medical conditions that affect people's quality of life. It is estimated that BD occurs in 70-84% of SCI patients [1]. Results are: under or overactive bladder, a-contractile bladder, or chronic urinary retention. SD occurs with a similar frequency and cannot be restored in 46% of cases [2], where most of them are young males in the phase of family building. 

Today's most common solutions for patients with BD include catheterization, external collecting devices, artificial detrusors, ileal conduit urinary diversion, and epineural sacral neuromodulation (ESN). Intermittent or indwelling catheterization is a low-cost, and low-risk solution and is the most commonly applied. Negative side-effects are elevated risk of infection and continuous catheterization which in SCI patients with higher levels can be difficult due to impaired limb motor functions. External solutions may appear unaesthetic and require constant care. Substitution is only applied in an overactive bladder. Artificial detrusors are used with overactive bladder and a-contractile bladder and are more invasive compared to the previous solutions. ESN has been shown to partially treat the beforementioned pathologies. Unfortunately, the success rate is low (29-44%), presumably due to low neural selectivity [4]. 

Regarding SD, today's solutions include the oral administration/ penile injection of pharmaceuticals, the implantation of an inflatable penile prosthesis, or epineural sacral neuromodulation (ESN). Oral administered pharmaceuticals can cause unwanted hypo- or hypertension and may not work in 30-35% of the cases [5]. Penile injections can be linked to scar tissue formation, penile pain, or infection [6]. A penile prosthesis, on the other hand, can cause infections or malfunctions, which are eventually linked to mechanical stability and reliability [7]. However, ESN has the potential to restore a physiological erection without unwanted side effects. ESN also has the great advantage of taking immediate effect, whereas pharmaceuticals, for example, have to be metabolized first. Today, however, using clinically applied neurostimulators, erections sufficient for penetration could be restored only in 50% of the cases [8]. 

The interruption of neural pathways in SCI patients is the leading cause of BD (overactive bladder, a-contractile bladder, or chronic urinary retention) or organic SD. As outlined above, various epineural electrodes exist to treat BD and SD in SCI patients. However, they cannot restore bladder function or full and natural erections with a high success rate. The goal of NERFPN is to restore bladder- and sexual function through the development of an intraneural electrode specifically tailored for the control of the sensory and motor nerve fibers of the pudendal nerve.

If you are interested in the progress of the project, would like to have more information, or are open to collaborating with us, please refer to the corresponding section!

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References:

[1] A. Alsulihem and J. Corcos, "Evaluation, treatment, and surveillance of neurogenic detrusor overactivity in spinal cord injury patients," Neuroimmunology and Neuroinflammation, vol. 6, Nov. 2019, doi: 10.20517/2347- 8659.2019.007.
[2] I. Tsuji, F. Nakajima, J. Morimoto, and Y. Nounaka, "The Sexual Function in Patients with Spinal Cord Injury," Urol Int, vol. 12, no. 4-5, pp. 270-280, 1961, doi: 10.1159/000277578.
[3] M. J. Hess and S. Hough, "Impact of spinal cord injury on sexuality: Broad-based clinical practice intervention and practical application," J Spinal Cord Med, vol. 35, no. 4, pp. 212-219, Jul. 2012, doi: 10.1179/2045772312Y.0000000025.
[4] M. T. Sanford and A. M. Suskind, "Neuromodulation in neurogenic bladder," Transl Androl Urol, vol. 5, no. 1, pp. 117-126, Feb. 2016, doi: 10.3978/j.issn.2223-4683.2015.12.01.
[5] C. N. McMahon, C. J. Smith, and R. Shabsigh, "Treating erectile dysfunction when PDE5 inhibitors fail," BMJ, vol. 332, no. 7541, pp. 589-592, Mar. 2006, doi: 10.1136/bmj.332.7541.589.
[6] K. Hatzimouratidis and D. G. Hatzichristou, "A comparative review of the options for treatment of erectile dysfunction: which treatment for which patient?," Drugs, vol. 65, no. 12, pp. 1621-1650, 2005, doi: 10.2165/00003495-200565120-00003.
[7] F. Montorsi et al., "AMS three-piece inflatable implants for erectile dysfunction: a long-term multi-institutional study in 200 consecutive patients," Eur. Urol., vol. 37, no. 1, pp. 50-55, Jan. 2000, doi: 10.1159/000020099.
[8] B. Giles Skey, "The finetech-brindley bladder controller notes for surgeons and physicians." 2002.