Sacral anterior root stimulator
An implantable medical device enabling patients with a spinal cord lesion to empty their bladders.
From 1969 onwards Brindley  developed the sacral anterior root stimulator, with successful human trials from the early 1980s onwards. Although both spinchter and detrusor muscles are stimulated at the same time, the slower contraction kinetics of the bladder wall (smooth muscle) compared to the spinchter (striated muscle) means that voiding occurs between the stimulation pulses, rather than during them.
This device is implanted over the sacral anterior root ganglia of the spinal cord; controlled by an external transmitter, it delivers intermittent stimulation which improves bladder emptying. It may also assists in defecation and may enable male patients to have a sustained full erection. The device is implanted in one of two regions, intra-thecally or extra-durally. It is often performed in conjunction with a dorsal rhizotomy, and many groups believe that the best results are only seen when this procedure is performed alongside the implantation. The rhizotomy will remove sensory reflexes, which in men may include sexual reflexes. For some patients this is a major handicap to the device. For others, the benefits outwiegh the downside.
The related procedure of sacral nerve stimulation  is for the control of incontinence in otherwise able-bodied patients.
- Brindley GS, Polkey CE, Rushton DN (1982): Sacral anterior root stimulator for bladder control in paraplegia. Paraplegia 20: 365-381.
- Schmidt RA, Jonas A, Oleson KA, Janknegt RA, Hassouna MM, Siegel SW, van Kerrebroeck PE. Sacral nerve stimulation for treatment of refractory urinary urge incontinence. Sacral nerve study group. J Urol 1999 Aug;16(2):352-357.
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