Page 111 - Bladder Dysfunction in the Context of the Bladder-Brain Connection - Ilse Groenendijk.pdf
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                 Acute effect of sacral neuromodulation for treatment of detrusor overactivity on urodynamic parameters 109
During chronic stimulation, when SNM has been active for 6 months, changes in the rCBF in brain areas involved in attention and alertness were detected.7 This, in turn, would result in less firing of the pontine micturition center (PMC) and restore bladder function. The fact that this rCBF change in the brain areas involved in attention and alertness is only detected after chronic SNM and not after acute SNM might be related to the working mechanism of SNM and could explain the differences in results in UDS be- tween acute and chronic stimulation. The areas predominantly involved in sensorimotor control showed a decrease in rCBF after chronic stimulation, instead of the increase in rCBF after acute SNM. This change might also explain the differences in results in UDS between acute and chronic stimulation.
The wash out duration of SNM has been investigated. Cadish et al. found a mean of 11.25 days before return of symptoms after turning the SNM off in 12 women with OAB.8 Altomare et al. detected that in 19 patients with urinary incontinence or fecal incon- tinence, the mean time to recurrence of symptoms after turning the SNM off was 3.4 months (range 0.9 – 13.5) and in 9 patients symptoms never returned.9 In conclusion, chronic effects of SNM seem to be maintained some time after stimulation is stopped, suggesting neuroplasticity of the involved brain areas. Moreover, the onset of action of SNM was recently investigated using bladder diaries which indicated that the mean time to 50% or greater symptom improvement was 3.3 days.29
These results, and those of the current study, suggest that a closed-loop feedback system, which activates SNM automatically when the detrusor pressure increases, would not be effective due to lack of acute effects after such short stimulation. However, on- demand and intermittent neuromodulation have been proved to be effective therapies in two separate trials.11,14 A possible explanation might be that in both trials, the patients were already using the SNM for > 7 years and 48 months, respectively.11,14 The above described neuroplasticity of the involved brain areas might already have been utilized, indicating that hypothetically, these neuroplastic changes can be maintained by inter- mittent or on-demand neuromodulation. Suggestions for future research in the use of a feedback neuromodulation system would be to investigate it with patients who are long-term users and who are starting users of SNM.
The main limitation of the current study is its small sample size. We initially aimed at a larger sample size. However, considering the absence of statistically significant findings in 8 successfully tested patients and the invasiveness of the UDS, we decided to stop inclusion for ethical reasons. In 4 patients, the first sensation of bladder filling was not noted because they had an involuntary detrusor contraction followed by direct urine leakage and micturition. Four patients had undergone a FSTLP after the PNE because of inconclusive PNE results. This inconclusive PNE was most likely caused by lead migration as all 4 patients described a loss of sensation of stimulation of stimulation after some days. Lead migration is a known disadvantage of PNE compared to a FSTLP and might be
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