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Bioengineering in Urology > Electrical Implants for the Neuropathic Bladder > Flashcards

Electrical Implants for the Neuropathic Bladder Flashcards

(43 cards)

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1
Q

Function of cerebral cortex

A

Conscious control of voiding

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2
Q

Function of pontine micturition centre

A

Co-ordination of bladder and sphincter contraction/relaxation

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3
Q

Function of sacral micturition centre

A

Detrusor contraction

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4
Q

Function of parasympathetic nerves

A

S2-S4 run in pelvic nerve

Detrusor contraction

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5
Q

Function of sympathetic nerves

A
  • T11-L2 run through hypogastric plexus

- detrusor relaxation/sphincter relaxation

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6
Q

Function of somatic nerves

A
  • pudendal nerves arising in Onuf’s nucleus

- sphincter contraction

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7
Q

What happens in the storage phase?

A
  • afferent impulses from stretch receptors to spinal cord
  • sympathetic efferents inhibit the detrusor and contract the internal sphincter
  • somatic efferents (pudendal nerve) contract the external urethral sphincter
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8
Q

What happens in the voiding phase?

A
  • afferent impulses from stretch receptor to pons
  • PMC activated if not inhibited by higher centres
  • parasympathetic efferents (S2-S4) contract detrusor muscle
  • sympathetic efferents relax bladder neck
  • somatic efferents inhibited, external urethral sphincter relaxes
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9
Q

What is the bladder function after SCI

A
  • interrupted normal control of bladder function blocking pathway between bladder and higher centres
  • function depends on level of injury
  • loss of voluntary control and development of aberrant reflexes that are not inhibited
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10
Q

Presentation of Upper Motor Neurone Lesion Bladder Dysfunction

A
  • lesion above SMC
  • bladder reflexes intact
  • loss of conscious control
  • loss of co-ordination
  • detrusor over activity
  • detrusor sphincter dys-synergia
  • autonomic dysreflexia
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11
Q

Lower motor Neurone Lesion Bladder Dysfunction

A
  • lesion below SMC
  • areflexic bladder and sphincters
  • loss of conscious control
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12
Q

How/Why does loss of conscious control present in an UMN lesion?

A
  • no voluntary bladder emptying

- lack of sensation of bladder fullness

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13
Q

Why is detrusor over activity in UMN lesions a problem?

A
  • small capacity bladder
  • reduced compliance
  • incontinence
  • high pressures = danger to upper tracts
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14
Q

Why is DSD in UMN lesions a problem?

A
  • high pressures

- incomplete empyting, infection

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15
Q

How/Why does loss of conscious control present in an LMN lesion?

A
  • no voluntary bladder emptying

- no sensation of bladder fullness

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16
Q

Why is weak sphincters and pelvic floor a problem in LMN lesions?

A
  • incontinence/ stress/ overflow
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17
Q

Why is an areflexic bladder a problem in LMN lesions?

A
  • large capacity bladder
  • chronic retention
  • poor compliance
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18
Q

What does management of the bladder after SCI aim to do?

Study These Flashcards
A
  • reduce pressures = protect upper tracts
  • facilitate emptying
  • improve capacity
  • reduce incontinence
  • improve quality of life
19
Q

What management options are there for the bladder after SCI? What do they do?

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A
  • antimuscarinics, Botox injections = reduce pressures
  • SPEC, ICS, urethral stenting, alpha blockers = allows emptying
  • clam ileocystoplasty = improves capacity
  • increase sphincter strength, AUS = reduce incontinence
20
Q

FES for restoring bladder function

Study These Flashcards
A
  • alternative option
  • control bladder by exploiting neuronal circuits
  • current state of the art
21
Q

How does FES work?

Study These Flashcards
A

Exploit neuronal circuits:

  • voiding phase (promotes bladder emptying via neurostimulatiion)
  • storage phase (reduces pressure and increasing capacity via neuromodulation)
22
Q

Sites for FES of the bladder

Study These Flashcards
A
  • bladder wall
  • sacral nerve roots (intra-thecal and extradural)
  • pelvic nerves
  • hypogastric nerves
  • spinal cord stimulation
  • pudendal nerves
  • pelvic floor
  • tibial nerves
23
Q

What is Intra-vesical Electrical Stimulation? How does it work?

Study These Flashcards
A
  • stimulating bladder mechanoreceptor afferents
  • catheter mounted electrode (cathode) placed in urethra
  • anode electrode on abdominal skin over pubic symphysis
24
Q

What has intra-vesical electrical stimulation been used for?

Study These Flashcards
A
  • children with underactive bladder due to spina bifida and hypo- or acontractile bladder in SCI
  • reports that it increased ability to empty bladder
  • however best results in hypocontractile bladder
25
Detrusor muscle stimulation Challenges
- difficult to keep electrodes in place over long period - concomitant contraction of external urethral sphincter due to stimulation of sensory nerves - high stimulation currents required
26
Pelvic nerve stimulation challenges
- lower currents required - difficult to access nerves - concomitant contraction of EUS
27
Finetech Sacral Anterior Root Stimulator (SARSI)
- implant restoring bladder function following SCI - electrodes placed on S2-S4 roots - intra-thecal or extra-dural - electrical stimulation (20-40Hz) causing bladder contraction - complete bladder emptying w/o need for catheters - usually combined with posterior rhizotomy to reduce over-activity
28
Parts of sacral anterior root stimulator implant (SARSI)
- external control unit - external cable - transmitter block - receiver block - implanted cable - electrodes
29
Benefits of SARSI with posterior rhizotomy
- complete bladder emptying with low residual - posterior rhizotomy - increased bowel function - implant driven erections
30
Why is complete bladder empyting with low residual an advantage with SARSI + posterior rhizotomy
- reduction in bladder infections | - eliminates need for catheters
31
Why is increased bowel function an advantage with SARSI + posterior rhizotomy
- increases bowel motility, moving stools down colon | - in some patients evacuation occurs by stimulation alone
32
Why is posterior rhizotomy an advantage?
- eliminates reflex incontinece - improved bladder compliance - reduces autonomic dys-reflexia (associated with bladder) - protects from kidney failure
33
Sacral Nerve Neuromodulation
- medtronic interstim targets sacral afferents entering spinal cord to modulate bladder reflexes reducing overactivity - tined electrodes placed on extra-dural sacral S3 nerves - implanted pulse generator - best results in OAB - early intervention in SCI reduced development of over activity
34
Percutaneous Tibial nerve Stimulation
- tibial nerve originates in L4-S3 lumbosacral plexus - stimulation thought to cause neuromodulation of bladder reflexes - less invasive than SNM - treatment given for 30 mins 1-2 times a week - used in OAB, MS, SCI - best results in SCI - may employ supra-spinal pathways - no large acute studies in SCI
35
Spinal cord stimulation
- good results in animal models - high complication rates - epidural electrodes now being developed for locomotor function - improved bladder function anecdotally reported - transcutaneous spinal cord stimulation
36
Pudendal nerve stimulation
- originates at S2-S4 of spinal cord - low frequency electrical stimulation (5-15Hz) of the pudendal nerves has been shown to effectively suppress bladder over activity - distally (dorsal genital nerve) becomes purely afferent - improved results compared with neuromodulation of whole sacral root
37
High Frequency Nerve Blocking
- high freq electrical stimulation (kHz range) of pudendal nerves can block motor axons to sphincter - possibility of reducing DSD and concomitant sphincter contraction during bladder stimulation - LT safety on human nerves not yet determined
38
Past, Current and Potential Research at RNOH
- SPARSI and SPAIRS - Surface Neuromodulation - Wearable devices - Pudendal blocking - Complete bladder function restoration
39
SPAIRS
- sacral nerve neurostimulation through Finetech SARS - no sacral de-afferentation - sacral neuromodulation through sacral electrodes
40
What does sacral neuromodulation through sacral electrodes do?
- extra-dural electodes (mixed nerve root) could not empty bladder due to reflex contractions of sphincter = need to block sphincter contraction - intra-thecal electrodes seperated motor and sensory nerves so could provide differentiated stimulation?
41
Optimization of neuromodulation site
- dorsal gential nerve - tibial nerve - sacral spinal cord
42
CARM
- wearable neuromodulation - conditional ano-rectal modulation - provides trans-anal neuromodulation to pudendal nerves lying in Alcock's canal - neuromodulation triggered conditionally on increase in sphincter EMG - trial in 6 SCI patients gave significant increase in bladder capacity and reduction in pressure - improved design - further clinical trials
43
Complete restoration of bladder function
- bladder emptying by stimulation of anterior roots - prevention of DSD by pudendal nerve blocking - conditional neuromodulation of NDO by pudendal nerve stimulation

Bioengineering in Urology (8 decks)

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