This device works by implanting a pacemaker-like neurostimulator in the lower back that sends mild electrical impulses to electrodes that are usually placed adjacent to the third sacral nerve root. The device received European Union approval in 1994 and USA FDA approval in 1999 and more than 35000 devices having been implanted worldwide to date. In patients with OAB, SNS restores the balance between inhibitory and excitatory control systems at various sites in the peripheral CNS. This involves stimulation of somatosensory ascending tracts projecting from the bladder into the pontine micturition centre in the brain stem. The electrical impulses also activate the pelvic efferent hypogastric sympathetic nerves, which promotes continence.
The device is inserted in two phases. The test phase includes the temporary insertion of a needle into the sacral foramen under local anaesthetic and the electrical stimulation is derived from an externally placed battery and generator. If the subject reports a satisfactory response after three to four weeks, defined as more than 50% improvement in symptoms, a permanent device is sited. This involves the implantation of a long-term battery and neurostimulator in the buttock and lower back.
A RCT reported continence outcomes of 47% at six month follow up, with a further 29% reporting more than 50% reduction in leakage episodes. A further systematic review confirmed these findings with 67% of patients reporting being dry or having a more than 50% improvement in symptoms. Another trial that followed patients up for a mean of more than 5 years reported continued success in 76% of the cohort.
Despite these success rates, this therapeutic option is not accessible to the majority of women largely due to the cost of the device and the expertise required to place and maintain the neurostimulator. It is available in South Africa, supplied by Medtronic, but retails for approximately R55000.
There are also significant adverse events associated with this equipment including pain and discomfort, seroma formation, disturbed bowel function and wound dehiscence.