Which of the following statements is CORRECT with respect to sacral anterior root stimulator (SARS)?A. At the time of implantation, it is usual to perform a concurrent dorsal rhizotomy, which involves dividing the posterior roots of S2 and S3
SARS is also known as the Brindley or Finetech-Brindley stimulator. The sacral anterior root stimulator was developed by experiments on baboons in the MRC Neurological Prostheses Unit in London from 1969 to 1977.
Activation of the implant stimulates contraction of both the bladder and the external sphincter. However, because the bladder is composed of smooth muscle and the sphincter-striated muscle, sphincter contraction is relatively short, and the detrusor continues to contract (and therefore empty) long after sphincter contraction is complete. This improves bladder emptying, reduces residual volume and infection and lowers transmitted upper tract pressures. The posterior roots are cut to control neurogenic overactivity. The improvement in bladder capacity and compliance is secondary to the dorsal rhizotomy and not the SARS.
The effects of implant activation on the bowel are increased colonic activity, reduced constipation and sometimes defaecation during stimulation. Dorsal rhizotomy causes loss of reflex erection but activation of the implant will cause a penile erection.