Sacral neuromodulation test with bilateral first stage tined lead procedure in patients with non-obstructive urinary retention: A pilot study

Neuromodulation through stimulation of the sacral nerves is a promising
therapeutic option in patients with symptoms of non-obstructive urinary
retention that are refractory to conservative treatment.
Each candidate for sacral neuromodulation (SNM) therapy is tested with either a
Percutaneous Nerve Evaluation test (PNE) or a first stage tined lead placement
test (FSTLP) before definitive implantation. During this test period the
integrity of the sacral nervous system and the reaction of the patient*s
symptoms to SNM are evaluated. Before (baseline) and during the test phase,
objective parameters such as the number of catheterizations per day, the voided
volume and the postvoid residual urine volume, are recorded in voiding
diaries. Patients that show an improvement of at least 50% in one of these
parameters are considered good candidates for SNM therapy and are implanted
with a definitive internal system.
Currently, both PNE and FSTLP tests are performed with unilateral stimulation
of the sacral nerve either on the right or left side of the sacrum. If a
patient shows no or less than 50% improvement of the objective parameters, he
is considered a bad candidate for SNM and the electrodes are removed. This
decision is currently based on a unilateral stimulation test. A study on
animals by Schultz-Lampel et al. suggests that bilateral sacral neuromodulation
can be a more effective technique for voiding dysfunction. They conclude that
bilateral stimulation may be more effective at lower stimulation intensities
with positive side effects such as longer stimulator-battery life and less
potential nerve damage. Clinical experience in different centers also suggests
that bilateral test stimulation may give a greater improvement in parameters.
Currently, only one prospective randomized crossover trial compared unilateral
approach with bilateral sacral nerve stimulation. In that study 13 patients
with urinary retention underwent unilateral as well as bilateral PNE test to
assess the possible advantages of bilateral stimulation. All patients were
stimulated during at least 72 hours in a unilateral and a bilateral setting
with a washout period of at least 48 hours between these two test periods.
Although the difference between unilateral and bilateral stimulation was not
statistically significant, the volume per void did not increase significantly
during unilateral stimulation but did increase significantly during bilateral
stimulation. The catheterized volume decreased significantly with no difference
between unilateral and bilateral stimulation. There were two patients who
started voiding during bilateral stimulation, whereas during unilateral
stimulation they were unable to void and still had to perform intermittent
catheterization.
The test used in the study by Scheepens et al was PNE. There are a few
important differences between the PNE and the FSTLP test. The advantage of PNE
test is that it is cheaper and less invasive than FSTLP test. The bilateral
FSTLP test is thus more expensive and more invasive. The removal of the lead is
also more invasive after FSTLP than after PNE.
A disadvantage of PNE test is lead migration with loss of effect after a short
time. This is not the case with FSTLP test because of the tines on the lead.
Furthermore the effectiveness is different. A recent study by Leong et al. has
shown that more patients with urinary retention responded to FSTLP than with
PNE (64% vs. 18%) (unpublished).
The findings by Scheepens et al. together with recent findings by Leong et al.
and the current patient population with retention are the basis for this study.

The objective of this study is to determine whether bilateral sacral nerve
stimulation with FSTLP test is more effective than unilateral stimulation,
among patients with non obstructive urinary retention.

A prospective cross-over pilot study will be conducted to evaluate whether
bilateral SNM test has an additional effect in patients with non obstructive
urinary retention compared to unilateral.
All patients will be implanted with bilateral tined leads. Before the patients
are implanted they are asked to fill out a voiding diary (baseline). The first
week after the implant they are asked to turn on the external pulse generator
only on one side to simulate a unilateral test. Currently, no data are
available that show or suggest a predominance of left or right side
stimulation. The second week, stimulation side is changed. During the third
week, patients are asked to turn the external pulse generator on both sides at
the same time. During each week patients are asked to fill out self recorded
voiding diaries for at least three days.

In this study all patient will undergo FSTLP as usual but bilaterally instead
of unilaterally. This means that two leads will be implanted instead of one.
And both leads will be connected to an external pulse generator.

The settings during this study are exactly the same as usual care. Frequency of
10 Hz, pulse width of 210 µs. The patient can change the amplitude to any level
between 0 and 10 volts. We ask the patient to keep the amplitude just below
sensory threshold.

The first week patients are asked to turn on only one of the external pulse
generator. This is to simulate a unilateral stimulation test. The second week
patients are asked to repeat the same procedure but this time on the other
side. The third week patients are asked to turn both external pulse generator
on. During each week patients are asked to keep a voiding diary for at least
three days.

If a patient has a good response unilaterally then the 2nd stage tined lead
placement will follow together with the removal of the other lead. If a patient
has only a good response bilaterally then the 2nd stage tined lead placement
will follow on both sides. If a patient has no response at all then removal of
both leads will follow.

Both PNE and FSTLP tests are usually conducted in a unilateral approach,
stimulating a sacral nerve on either the right or left side of the sacrum. If a
patient has no response to the test then complete failure of SNM therapy is
assumed and the lead will be removed. However, there are some clinics that
suggest conducting bilateral test stimulation to obtain better results. A study
by Scheepens showed that among 13 patients with retention, two responded to
only bilateral stimulation. A benefit for a patient who is included in this
study is that he may have a greater possibility to respond to sacral
neuromodulation, and therefore reduced need to intermittent catheterization.

Bilateral FSTLP procedure has in theory a higher risk of infection and bleeding
due to a double number of wounds compared with unilateral. Because the risk
when conducting the FSTLP unilaterally is very small, we consider the risk for
bilateral FSTLP to also be very small. The burden for the patient is minimal.
The number of operations are the same, although the operation time is going to
be around 15 minutes longer then unilateral FSTLP procedure. The period for
unilateral and bilateral FSTLP test is equally long, although during bilateral
FSTLP a patient has to fill out a voiding diary for in total of nine days
instead of seven days.