Sacral neuromodulation (SNM) is one of the recommended treatment options for refractory overactive bladder syndrome (OAB), it involves a two staged procedure. The first stage (test phase), usually lasts for one to two weeks and can be done either with a basic or an advanced evaluation. The basic evaluation is conventionally known as PNE (percutaneous nerve evaluation). Alternatively, the advanced evaluation consists of a quadripolar tined lead insertion that is used for the test phase. Traditionally, the basic evaluation or PNE is done by inserting a temporary monopolar lead using specific body landmarks without the routine use of fluoroscopy.
The recent International Continence Society Standardization document has suggested that the advanced evaluation has a better conversion rate to a permanent implant (80%) than the basic evaluation (44-52%) [1]. The aim of this study is to look at the conversion rate using the basic PNE under fluoroscopic guidance and under local anaesthesia in the outpatient setting.

Retrospective review from May 2012 to September 2018 of 215 patients with refractory detrusor overactivity and/ or voiding dysfunction that were treated with PNE (basic evaluation) using fluoroscopy. Total costs of PNE and advanced tined lead phase at our centre were also compared.

Overall, our SNM success rate was 73%. Out of the 215 patients who had PNE, 201 (93%) were done using fluoroscopy. For 59 patients who had a successful PNE insertion, there was no improvement in their symptoms therefore, they were not suitable for the permanent implant and had different treatment. 12 patients needed to have an advanced evaluation (quadripolar tined lead) as a repeated test phase due to monopolar (PNE) wire migration. A total of 130 patients (65%) had a successful PNE and as a consequence, they had the insertion of a tined lead and battery (permanent implant). Moreover, our review showed that when PNE is done under a local anaesthetic in a procedure room using X-Rays it comprises 24% of the total cost of the advanced tined lead phase.

For the test phase, the advanced tined lead has the best conversion rate (80%), However, when compared with the literature our conversion rate from PNE using X-Rays to tined lead and battery (permanent implant) is significantly higher (44-52% Vs. 65%). This new information can be of some benefit when updating the best practice statements for the use of SNM and also when deciding different treatment options. Only 6% of our patients needed to have an advanced tined lead test phase repeated due to original PNE monopolar wire migration within the two week test phase. This means that for the majority of patients who had their PNE monopolar wire inserted under fluoroscopy it was reliable, well tolerated and effective.  
Also, doing PNE under local anesthetic as a day case procedure reduces the hospital costs significantly. The analysis of the costs of the two test phases includes equipment, consumable materials and staff expenditures. Performing PNE as a standard procedure for patients with refractory detrusor overactivity and/or voiding dysfunction reduces the total outlay by approximately three quarters. This can also be used as a reference when deciding between the two modalities of test phase. Additional savings are also created at the lead removal stage. As this can be done in the outpatient setting unlike the advanced tined lead which, if the patient fails to respond, would need to be removed in the operating room under anaesthesia.

Our conversion rate from PNE using fluoroscopy to full system implant was 65% therefore; it is a safe, less invasive and less expensive method. Moreover, it has a similar conversion rate when compared to advanced test phase for the first stage.

Goldman, H. (2019). International Continence Society best practice statement for use of sacral neuromodulation. [online] Ics.org. Available at: https://www.ics.org/Documents/DocumentsDownload.aspx?DocumentID=5254 [Accessed 29 Mar. 2019].