4th Annual Jefferson Urology Symposium: Focus on Urinary Incontinence

© The Canadian Journal of Urology TM : International Supplement, August 2021 TABLE 2. Sacral neuromodulation devices Device Size MRI compatibility Battery life InterStim 14 cm 3 Head 1.5T 4-5 years InterStim Micro 2.8 cm 3 Full Body 1.5T + 3T 15 years (rechargeable) Axonics r-SNM 5.5 cm 3 Head 1.5T + 3T 15 years (rechargeable) Full body 1.5T TABLE 1. List of medications for overactive bladder Trade name Generic name Class Vesicare Solifenacin Anticholinergic Toviaz Fesoterodine Anticholinergic Sanctura Trospium Anticholinergic Detrol Tolterodine Anticholinergic Enablex Darifenacin Anticholinergic Ditropan Oxybutynin Anticholinergic Myrbetriq Mirabegron ß3-agonist Gemtesa Vibegron ß3-agonist exhibited high sensitivity to this medication class, narrow angle glaucoma, gastroparesis, and cognitive impairment. Of note, recent studies have also shown an association between anticholinergic medications and increased brain atrophy, dysfunction, and clinical decline. 23 Anticholinergic medication adherence is a known issuewith up to 89%of patients reporting either unmet treatment expectations and/or tolerability as the reason for discontinuation. 15,24 ß3-agonists have shown similar efficacy to anticholinergics but offer a different side-effect profile. 25 Mirabegron side-effects include headaches, nasopharyngitis, and elevated systolic blood pressure. It is contraindicated in patients with uncontrolled hypertension. Mirabegron is metabolized by cytochrome P450 CYP3A4, as well as CYP2D6, so there is a risk of drug-drug interactions. 26 Approved by the FDA in 2020 following the results of the EMPOWUR trial, Vibegron is the second and newest medication in the ß3-agonist class. 27 Unlike mirabegron, it is metabolized independently from CYP3A4, 2D6, and 2C9 and less likely to cause drug-drug interactions. It is also not associated with an increase in systolic blood pressure. An important factor that will also impact the choice of pharmacologic agent is drug cost and insurance coverage. Third line treatments for OAB include various forms of neuromodulation such as peripheral tibial nerve stimulation (PTNS), sacral neuromodulation (SNS), and chemodenervation via onabotulinumtoxinA. 16,17 PTNS and SNS are both forms of neuromodulation that have been described in the literature since the 1980s. 28,29 PTNS involves stimulation of the tibial nerve which is a mixed motor and sensory nerve innervated by L4-S3 roots. Electrical stimulation of the posterior tibial nerve causes retrograde neuromodulation of the bladder and pelvis floor which shares common innervation from the sacral nerve plexus. Stimulation is delivered via a battery powered stimulator connected 34 gauge needle electrode inserted above the medial malleolus. 30 Treatment involves 30 minute weekly sessions for 12 weeks. Maintenance therapy is once a month. Absolute contraindications to PTNS include pregnancy and presence of a pacemaker or defibrillator. Relative contraindications include peripheral neuropathy, peripheral edema, and neurogenic bladder. Complications of treatment are minimal but consideration must be given to the time commitment required by the patient. Sacral neuromodulation (SNS) for OAB has been FDA approved since 1997 and there are currently three devices on the market, Table 2. 31,32 It involves direct stimulation of the S3 nerve root of the sacral nerve plexus that modulate the reflexes influencing the bladder, urinary sphincter, and pelvic floor. 33 It is a two staged procedure that requires an initial temporary lead placement to check for at least 50% improvement in patient symptoms. After this has been confirmed, the second stage of the procedure involves surgically implanting a permanent pulse generator. During the procedure, proper S3 lead placement is confirmed by observing bellows of the perineum and plantar flexion of the big toe. Complications from the procedure include device infection which would require explantation and loss of efficacy due to lead migration. Contraindications, like for PTNS, include pregnancy and presence of a pacemaker or defibrillator. It should be noted that anti-coagulation 29 Evaluation and management of female urinary incontinence