Safety and Tolerability of a Novel Implantable Neurostimulator for Ameliorate Erectile Function on Spinal Cord Injured Patients

Depending on the location and whether the spinal cord lesion is complete or not, oral medications (phosphodiesterase type 5 (PDE5-Is) inhibitors, eg Viagra®) may be more or less effective in improving erectile function. When these drugs are not sufficiently effective, the second-line pharmacological treatment for SCI patients consists of intracavernous injections. Treatment by intracavernous injections is responsible for additional constraints. Indeed, a titration must be carried out in a doctor's office (important to minimize the risk of priapism). Specific learning of the injection technique must also be implemented for the patient and/or his partner, the identification of the injection site (laterally in the cavernous bodies at an angle of 90° with respect to the long axis of penis, avoiding the urethra and subcutaneous veins) and aseptic handling. The use of intracavernous injections is often abandoned by patients due to a high level of discomfort, complicated self-injection or lack of spontaneity during sexual intercourse. In patients with SCI, intracavernous injections of prostaglandin E1 fail to induce a sufficiently rigid erection in 20% of them. Vacuum device is another option. Nevertheless it may be perceived as cumbersome and lacking of spontaneity. In case of failure or lack of acceptance of intracavernous injections and vacuumdevice, the penile implant, which consists of a pair of malleable or inflatable cylinders surgically implanted in the cavernous bodies previously destroyed surgically, is the third-line treatment. However, penile implants have an increased risk of infection in patients with SCI, according to two large studies. Thus, effective, acceptable and safe treatment alternatives are sought by patients with SCI who are insufficiently responsive to oral treatments.

The concept of electro-neurostimulation therapy to activate the cavernous nerves for erectile dysfunction was introduced two decades ago. Despite its recognized potential and the first promising studies confirming the feasibility of peri-prostatic cavernous nerve stimulation, this technology has not yet been developed. The difficulty lies in the complex anatomy of the human cavernous nerve. Indeed, it is difficult to identify the optimal site for stimulation because the human cavernous nerve is not visible on a macroscopic scale and extends from the pelvic plexus to the penis through a peri-vesical and peri-prostatic neuroplexus. whose anatomy is complex. In addition, the course of the cavernous nerve is subject to strong interindividual variability. In addition to these intrinsic anatomical problems, other difficulties are encountered during the surgical intervention, such as the presence of overlying tissues, connective tissue and potential bleeding obstructing the operative field, thus making the optimal placement of the implants complex.. The main difficulty in applying neurostimulation to the treatment of erectile dysfunction is therefore to identify the stimulation site to place the stimulation electrodes in optimal contact with the cavernous nerve.

A practical solution was invented by a patch with twelve electrodes. This solution was designed to promote extensive contact with the cavernous nerve. The concept was developed to allow implantation of the electrodes regardless of the visibility of the cavernous nerve bundles. This concept makes it possible to globally cover the anatomical region of interest where the cavernous nerve is supposed to be located, while taking into account the great heterogeneity of its course. This approach then guarantees optimal contact of at least a few electrodes with the cavernous nerve and thus offers optimal stimulation conditions.

The multi-electrode patches will be implanted during a robotic laparoscopic surgical procedure. A stimulation test will be performed during the operation to ensure that the patient responds to stimulation (erectile response) before the device is permanently implanted. Following the recovery of the patient, the selection of the stimulation parameters will be carried out on an outpatient basis in order to identify the electrode(s) which give(s) the best erectile response. The electrodes in contact with the cavernous nerve bundles (causing the maximum erectile response) will then be selected and recorded for stimulation/therapy.