Neuromodulation adverse events characterized

Researchers recently presented 12-month follow-up data from a prospective, multicenter trial of a device for sacral neuromodulation.

Montreal-The majority of adverse events that occur with sacral neuromodulation therapy to treat overactive bladder (OAB) do not require surgical intervention, according to 12-month findings from a prospective, multicenter study.

"We wanted to drill down to identify the most important adverse events and what events required intensive (surgical) intervention," said first author Karen Noblett MD, of the University of California Riverside School of Medicine, Riverside, who presented the findings at the International Continence Society annual meeting in Montreal.

Dr. Noblett and co-investigators presented data out to 12 months’ follow-up of a 5-year, prospective, multi-center trial for sacral neuromodulation using InterStim (Medtronic) to manage OAB.

"We want to have realistic data for physicians to counsel patients on what they can expect and what the chances are of needing a revision. We want to identify lessons learned so we can improve (our practices)," said Dr. Noblett.

An initial 340 study subjects underwent test stimulation, and 272 subjects received the sacral neuromodulation implant. The vast majority (91%) of subjects were female, and the mean age was 57 years.

Next: Adverse events

There were 36 adverse events related to undesirable change in stimulation in 32 subjects. A total of 26 adverse events were related to implant site pain and occurred in 20 study subjects. Ten of the 20 study subjects who had implant site pain (3.7% or 10 of 272) required surgical intervention on the device. There were a total of 12 adverse events related to implant site infections that occurred in nine subjects, with surgical intervention required in seven subjects (2.6%). All four lead fractures (1.5%) in four patients necessitated surgical intervention resolved by replacement. All three cases of lead migration or dislodgment required surgical intervention where the device was replaced with resolution of symptoms.

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A total of 22 adverse events (8%) required revision and/or replacement, while a total of 13 (5%) patients underwent explantation.

"The two most common reasons for surgical intervention were infection and pain at the site of implantation," said Dr. Noblett, noting other reasons for surgical intervention was lack or loss of efficacy of the device, patient request, or battery replacement.

While there were a total of 82 device-related adverse events or a rate of 30%, the total surgical intervention rate was 13% (35 of 272).

Next: "Most adverse events were minor in nature and were resolved without any surgical intervention."

"Most adverse events were minor in nature and were resolved without any surgical intervention. Patients may not have felt the stimulation because it was not on or they had accidentally turned off the stimulation. Reprogramming (of the InterStim System) would be considered a minor adverse event. Only one reprogramming case required surgical intervention,” Dr. Noblett said.

The study did not employ a specific antibiotic prophylaxis protocol to avoid infection, but since that was one of the most common reasons for explantation, that will be a consideration for the future to reduce this risk.

Additionally, most infections occurred within the first 30 days of implantation of the device.

"That is not surprising because that is when the surgical site is open. It would be unusual for patients to do well (after surgical intervention) and then present later on with an infection,” Dr. Noblett explained.

Greater knowledge about optimal placement of the implant will likely avoid the need for surgical intervention post-implantation, added Dr. Noblett.

"One of the most common reasons for surgical intervention was due to implant site pain, many of which were attributable to the IPG (implantable pulse generator) being placed in the wrong position, requiring revision of the device," she said.

The study was sponsored by Medtronic.