*2.2.9.3 Implant infection*

*Neurostimulation and Neuromodulation in Contemporary Therapeutic Practice*

are checked and patient compliance is evaluated [42].

limited to isolated case reports and limited series [73].

*2.2.9 Adverse events and complications*

*2.2.9.1 Pain*

associated with trauma.

of the pocket or implant [73].

quently altering the settings [42].

*2.2.9.2 Undesirable change in stimulation*

fail to correct the deficiency [42, 75].

tested and tried out and allows them to choose their preferred settings. At our center this is done on the next day postoperatively and ensues removal of the urinary catheter placed during the procedure to allow for trials of voiding [41, 70]. Patient follow-up is periodic thereafter, during which voiding and stimulation parameters

Good communication between the patient, surgeon and the programmer are necessary to obtain the optimum results and efficacy of SNM. In cases where any unforeseeable event occurs, such as sudden loss of efficacy or any of the adverse events that will be discussed as follows, proper testing of the programs and circuit impedance, as well as efforts at reprogramming operational electrodes should be utilized extensively

Adverse events associated with SNM are numerous and well-documented. The majority of such events are anticipated and even counseled for preoperatively, with a documented range of 16–30% between the test and final implantation stages. Unanticipated or unexpected adverse events and complications are rare and are

Implant site pain is pain perceived at the site of the IPG. This could be the result

Another cause of pain could be stimulation program related. Turning off the IPG can differentiate between IPG-related and program-related pain, the latter usually requiring changes in stimulator settings by the programmer [42]. In the most debilitating cases, and often, this complaint would require surgical revision

Pain could also be felt at the site where the stimulatory sensation is perceived, and this too, could often be differentiated by turning off the stimulator, and subse-

Perhaps one of the most unfortunate adverse events is an undesirable change in stimulation that leads to loss of a successful SNM effect or subjective dissatisfaction with an objectively successful implant. In one series, researchers reported this to occur in 12% of their surveyed adverse events in SNM implants for OAB. The majority of such incidences can be corrected with simple or sometimes more complex reprogramming of the neuromodulator, and rarely requires revision or explantation [73]. However, decrease in efficacy of stimulation is a major reason for reoperation and explantation should reprogramming in absence of lead migration

Checking the impedance can be useful to assess for any possible lead breakage or dislodgement which would show high impedance, but if the impedance is less than 50 ohms, this may indicate a short circuit that could be due to a wet connection.

of many reasons. A too-superficial implant may be cutaneously felt and pose a source of discomfort especially if implanted at a lower gluteal point and as such would be "sat on" by the patient. In one review, the most commonly cited reason for explantation was site pain [74]. Another series reported this to occur in 7% of implants, with the majority presenting beyond 30 days of implantation and some

before reaching the morbid decision of revision or explantation [42, 71, 72].

**224**

In a multicenter retrospective case–control assessment of risk factors for explantation of the SNM device due to infection, researchers reported on an almost 2–3% incidence of infection and identified that hematoma formation and IPG pocket depth of greater than 3 cm were independently associated with development of infection, while implant infection was the leading cause of device explantation at 1 year follow-up in another large trial [68, 73, 76]. The most common pathogen reported on cultures obtained from these explants was the skin flora resident *S. aureus*. Infection is probable both early in the postoperative period within 30 days of implantation, or later beyond 30 days and sometimes up to 10 months post-implantation [73, 76].

Risk factors associated with SNM implantation infection have been studied, and some have been refuted. The choice of preoperative antibiotic regimen is of importance in both stage I and final IPG implant, and the antibiotic administered should target potential and common skin organisms such as *S. aureus* [62].

Prevention of such infections has also been reviewed. One group of researchers reported on the use of an antibiotic-coated collagen layer placed over the IPG before wound closure with noticeable results. Skin preparation is also important, particularly with chlorhexidine-based solutions per international recommendations [62, 68]. And although many surgeons still do administer certain courses of post-implantation antibiotics, this is not supported by any clinical evidence of benefit, though further research may better define its role as is the case with other prosthetic or implantable devices [62].
