DESCRIBE IN DETAIL ABOUT THE USE OF SACRAL ANTERIOR ROOT STIMULATOR FOR NEUROGENIC BLADDER ?
A 1 INTRODUCTION
1 From 1969 onwards Brindley developed the sacral anterior root stimulator, with successful human trials from the early 1980s onwards.
2 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.
3 A ) In 1969, Brindley developed sacral anterior root stimulator (SARS) and first tested in baboons [Brindley
B ) In 1976, stimulator was first successfully implanted in human [Brindley 1993].
C ) Early SARS devices were often implanted without rhizotomy.
D ) SARS became usually combined with posterior sacral
root rhizotomy, with being restricted to S2-3.
Most procedures have been done in European regions (over 1500 systems till year 2002).
DESCRIPTION
1 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.
2 It may also assists in defecation and may enable male patients to have a sustained full erection.
3 The device is implanted in one of two regions, intra-thecally or extra-durally.
4 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.
5 The rhizotomy will remove sensory reflexes, which in men may include sexual reflexes ( V IMP - VIVA Q ). For some patients this is a major handicap to the device. For others, the benefits outwiegh the downside.
6 The related procedure of sacral nerve stimulation is for the control of incontinence in otherwise able-bodied patients.
7 so , in the end we can say that High pressure of bladder contraction enough to empty the bladder can be achieved by stimulating the sacral anterior root that innervate the urinary bladder.
- Mechanism of Action
Electrical stimulation of sacral anterior root:
A ) activate the detrusor muscle that causes bladder emptying
B ) activate urethral sphincter
C ) activate pelvic floor muscles to reduce the number of incontinence episodes
D ) lTheoretically: Stimulation of anterior sacral root causes simultaneous contractions the detrusor muscle and the urethral sphincter (thus electrically induced DSD) and pelvic floor musculature.
E ) Actually: The bladder is successfully emptied.
Upon stimulation, striated sphincter contracts and relaxes more rapidly
F ) while bladder smooth muscle contraction is slow-onset and more sustained.
G ) Therefore, with the intermittent stimulation with bursts of electrical impulses, constant bladder pressure can be maintained during the stimulation intervals while the sphincter periodically relaxes allowing urine to flow in between stimulation.
H ) Ultimate emptying of the bladder can be achieved but it requires multiple sessions of stimulation.
Advantages of combined posterior rhizotomy: [Popovic 2002]
A ) to eliminate all reflex activities of the detrusor
B ) to reduce hyperreflexia of the bladder (increasing bladder capacity and compliance)
C ) to reduce DSD (which improves urine flow)
D ) to reduce reflex incontinence (which protects upper urinary tracts from uteric reflux and hydronephrosis).
- Terminology
neuroproshesis
- Purpose of this procedure
A ) to increase bladder capacity
B ) to maintain low-pressure storage of urine with preservation of the upper urinary tract
C ).to prevent incontinence
D ) to achieve bladder emptying
- Indication
1 neurologically stable suprasacral and clinically complete SCI with intact peripheral parasympathetic innervation to the bladder v imp
2 paraplegia/ tetraplegic SCI patients with
uncontrollable urinary incontinence
3 DSD
4 Severe autonomic dysreflexia
5 Unbalanced voiding
6 Insufficient detrusor contraction
- Procedure
1 Implantation can be done either in the extradural or intradural manner.
2 Laminectomy at L3-S1 [Brindley 1982]
3 Posterior rhizotomy
4 Electrodes are placed bilaterally on the mixed S2 roots (channel B) and bilaterally on the mixed S3 and S4 roots (channel A).
5 The cables are tunneled to a subcutaneous pocket on the lower part of the thorax or on the abdominal wall and connected to the radioreceiver block.
6 Successfully established device for bladder and bowel emptying in SCI
usually accompanied by a rhizotomy of the posterior (sensory) sacral roots
- Commercially available Device
Finetech-Brindley Sacral Anterior Root Stimulator (SARS or Vocare, Finetech Medical Ltd. United Kingdom / NeuroControl, Cleveland, USA)
- Advantages
A ) bladder emptying on demand with minimal residual urine volume
B ) Significant reduction in the number of UTI
elimination of urethral catheter, thus improvement of QOL and social ease
C ) Enhanced bowel control
D ) Safe, effective and limited morbidity
E ) Potential long-term cost saving: from decreased urinary tract complications
- Disadvantages
A ) Cost
B ) alloplastic-related infections
C ) mechanical failure of the implant
D ) Major surgery
additional damage to the nervous system (dorsal rhizotomy)
- Current Significance
A ) The procedure can produce micturition with low residual volumes of urine and reduced urinary tract infection in patients with suprasacral spinal cord injury.
B ) This also increases bladder compliance, which may be protective for the upper urinary tracts.
- Other uses
A ) Synchronous stimulation of parasympathetic fibers innervating the penis is used to obtain erections.
B ) A reduction in constipation usually is observed, and some patients are able to defecate with the aid of electrical stimulation.
C ) Penile erection is produced in a substantial proportion of male patients.
D ) The nerves do not appear to be damaged by long-term stimulation. [Creasey 1993]