Implantable neuromodulation device safe, effective in overactive bladder patients
The implant of a tibial nerve stimulator device for overactive bladder (OAB) appears to yield significant improvements in symptoms and quality of life (QoL) without inducing walking disturbances or pain at the implant site, according to a study.
A total of 15 refractory OAB patients (mean age 54 years; 87 percent female) received the implant of a battery-free device for tibial nerve stimulation. Of these, 80 percent had urinary incontinence (OAB-wet) and 33.4 percent were previously treated with percutaneous tibial nerve stimulation (PTNS). None underwent urinary incontinence surgery in the past 6 months or abdominoperineal resection of the rectum.
Data from the 3-day bladder diary and 24-hour padtest showed significant improvements in several parameters from baseline to 3 months after the activation of the device, as follows: 24-hour urinary frequency (from 11.8 to 8.1 times/day; p=0.002), number of severe urinary urgency episodes (from 6.5 to 2.0 times/day; p=0.002), severe incontinence episodes (from 2.8 to 0.3 episodes/day; p=0.017) and urinary loss/day (from 243 grams to 39 grams; p=0.038). One patient had the implant removed due to pain and swelling, although tissue cultures did not reveal a bacterial infection. [J Urol 2017;doi:10.1016/j.juro.2017.01.078]
Likewise, QoL significantly improved (p=0.001 on ICIQ-Female Lower Urinary Tract Symptoms [FLUTS]; p=0.002 on Urogenital Distress Inventory [UDI]). ICIQ-FLUTS improved in 13 patients and remained unchanged in one, with eight patients demonstrating >50 percent improvement in their bother-score. On the other hand, UDI improved in 12 patients and deteriorated in two, with the bother score showing >50 percent improvement in five patients.
All 14 patients stimulated six times a week, once daily for 30 minutes, with a minimal sensation amplitude of 2.4 mA and maximum tolerable levels of 7.0 mA. An external control unit that wirelessly powered the implant (a 25 mm cylinder with a diameter of 3.4 mm and four tiny fixating wings) provided the therapeutic parameters and allowed stimulation to be performed at a pulse width between 50 to 800 µsec, an amplitude range of 0 to 9 mA, and a frequency of 5, 10, 20 and 40 Hz.
During the 3 months of follow-up, 6 patients stimulated with 20 Hz and 200 µs, four with 10 Hz and 200 µs, two with 5 Hz and 200 µs, one with 5 Hz and 800 µs, and one with 40 Hz and 200 µs. Patients had been able to only adjust the stimulation between a patient-specific set minimum and maximum.
Having been established as a safe and effective treatment for OAB refractory to conservative treatments, neuromodulation targets the innervation system that controls the pelvic floor organs. Standard neuromodulation systems involve the delivery of a stimulus to the sacral (sacral nerve stimulation, SNS), pudendal (pudendal nerve stimulation) or tibial nerve (percutaneous tibial nerve stimulation, PTNS), all of which affect central components of the neural circuits controlling the bladder. [Nat Rev Urol 2013;doi:10.1038/nrurol.2013.143; Curr Urol Rep 2012;13:327–334]
Compared with PTNS that use a needle electrode, one of the principal advantages of implant-driven neuromodulation is that “patients can treat themselves outside the hospital, at a convenient time, as often as necessary for the best therapeutic benefit, without the need for needle insertion,” researchers said.
“An additional advantage the tibial nerve implant holds in comparison to SNS devices is the simple and short duration of the implantation procedure. The tibial nerve at the ankle level is easy to access, and the small and compact design of the implant minimizes pain at implantation site. Moreover the tibial nerve implant is leadless so lead breakage cannot occur in contrast to other implants,” they added.
In the cohort, the median skin-to-skin operation time was 34 minutes, with all patients being operated under general anaesthesia, although it might be possible to perform the implantation under local anaesthesia in an outpatient setting, researchers noted. Only three patients had a prolonged antibiotic treatment, while three patients had prolonged pain medication (1 week for both).
The findings highlight the potential implementation of the new implant technique in clinical practice, but further research is warranted to determine how often stimulation is necessary to reach and maintain an optimal therapeutic effect, they said.