Neuromodulation

Bladder and bowel functions are controlled by interactions between the voluntary and autonomic nervous systems. These interactions can be disrupted by spinal cord injury (SCI), leading to high bladder pressures, urinary and faecal incontinence, and potential kidney failure.

Restoration of pelvic functions remains one of the priorities of spinal cord-injured people. Bladder and bowel management featured three times in 10 priorities identified by the James Lind Alliance and Spinal Cord Injured charities.

Our research investigates the acute effects of neuromodulation on bladder spasticity to determine the optimum anatomical site for the reduction of bladder overactivity in patients. This will allow us to conduct more research into optimum stimulation regimes and triggers, and develop a non-invasive, versatile, wearable device which can control these dysfunctions.

Case study: Ambulatory Urodynamics

Background

Current management therapies for bladder and bowel dysfunction include pharmaceutical and surgical techniques.

Anti-muscarinic medication such as oxybutynin, solifenacin and tolterodine prevent incontinence by blocking the action of the neurotransmitter at the neuro-muscular junction. However, anti-muscarinic medications are not specific to the bladder and cause side effects such as blurred vision, constipation, and dry mouth.

Surgical techniques include injections of the neurotoxin, onabotulinum toxin A directly into the bladder wall to cause temporary paralysis. This technique requires costly repeat injection every 9-12 months and has occasionally caused systemic paralysis. More invasive and irreversible techniques include clam ileocystoplasty.

Electrical stimulation (also known as neuromodulation) of the sacral and pudendal nerves has been shown to inhibit unwanted bladder contractions, thereby increasing capacity, improving continence, and reducing potential for damage to kidneys. Our studies also show that neuromodulation can alleviate symptoms of lower limb spasm and bowel dysfunction.

Neuromodulation is thought to occur through modulation of the supra-sacral and segmental reflexes pathways at the sacral level. Continuous neuromodulation has been applied both through implanted devices delivering stimulation directly to the sacral nerves, and non-invasively through surface stimulation of dorsal penile (clitoral) nerves, a branch of the pudendal nerve, and through the posterior tibial nerve.

There are reports of the benefits of transcutaneous spinal cord stimulation on lower limb spasticity and bladder control, though there is limited research on the acute effects of this technique on NDO. At present, there are CE marked devices for sacral nerve neuromodulation through an implant (Medtronic Interstim) and percutaneous devices for PTN stimulation (Uroplasty Urgenct PC). These devices are expensive, invasive, and have not been shown to be as effective in spinal cord injured patients compared to other groups, e.g., over-active bladder syndrome (OAB).

Several research studies, including our own, show excellent results on the acute effects of neuromodulation to control unwanted bladder contractions in spinal cord injured patients. There are not currently any commercially available externally worn devices to translate this technique to clinical practice. They would offer an alternative to expensive implants, medical or surgical managements.

Study details

Our research investigates the acute effects of neuromodulation (electrical stimulation of neural pathways to modify their activity) on bladder spasticity with respect to stimulation site, to determine the optimum anatomical site for reduction of bladder overactivity in patients with Spinal Cord Injury (SCI).

To discover the most effective transcutaneous stimulation site, we are investigating the efficacy of neuromodulation at three distinct anatomical sites: 

1. Dorsal Penile Nerve (DPN), 
2. Posterior Tibial Nerve (PTN)
3. Spinal Cord (SC).

We will monitor bladder activity and pressures during standard urodynamics performed both with and without stimulation in up to 20 participants.

First, a standard cystometrogram (CMG) will measure bladder capacity and activity before any stimulation takes place.

Electrodes will then be placed on the skin over one of the three identified sites (a different one each session) and the stimulation intensity will be set. 

A second CMG will then be performed, during which stimulation will be started each time the pressure in the bladder rises because of unwanted contractions.

If the neuromodulation positively impacts bladder overactivity, a third CMG will be performed, using stimulation that is started by the participant based upon feelings or signals that may indicate bladder overactivity.

This will allow us to research optimum stimulation regimes and triggers, and develop a non-invasive, versatile, wearable device which can control these dysfunctions in patients with a spinal cord injury.

Our 'Stim to Stand' study for spinal cord injury patients applies electrical stimulation to the lower back to 'wake up' inactive connections in the spinal cord. This has enabled people with long-standing spinal cord injuries to regain some movement in their legs. 

People have also reported improvements in bladder control. Restoring bladder control is a high priority for spinal injury research, but the carry-over effect from leg muscles to the bladder has not been studied scientifically.

We are investigating whether spinal stimulation enables people with spinal injury to stand up, and whether regular sit-to-stand training plus spinal stimulation improves: 1) standing ability, 2) bladder control, 3) well-being.

Background

An injury to the spinal cord can cause partial or complete loss of sensation and movement in the body from the point of the injury and below. In many cases, this can be life altering.

With a 'complete' injury to the cord, the affected individual is unable to move their legs and uses a wheelchair for the rest of their life. However, even after a ‘complete’ injury, it is common for some connections in the spinal cord to survive, but in an 'inactive' or 'sleeping' state.

Applying electrical stimulation to the lower back (spinal stimulation) appears to awaken these connections, allowing some previously unavailable leg movements. 

The first time they had spinal stimulation, people with long-standing 'complete' spinal cord injuries became able to move their legs. After several weeks of treatment, these movements seemed to increase. People having regular spinal stimulation also noticed other changes, including improvements in their bladder control. Restoring control of the bladder is one of the highest priorities for spinal injury research but this carry-over effect from leg muscles to the bladder has not been studied scientifically.

Standing is a recommended activity for people with spinal cord injury. Most do stand regularly because of benefits to their muscles and joints. But this is usually done ‘passively’ (with no muscle activity) in a standing frame.

The benefits of standing up using leg muscles are far greater. Spinal stimulation (applied using implanted electrodes in the lower back) has caused strong leg extension movements in people with spinal cord injury, which may allow them to stand up. So far, at least four people have been able to stand with this treatment - one for an entire American football game.

But implanted electrodes are costly and invasive. Spinal stimulation using surface electrodes is simple and cheap, but we don’t yet know whether it is as effective. At least one person has stood using stimulation treatment with surface electrodes, supported by one fingertip on a standing frame. If surface stimulation does allow people with spinal cord injuries to stand with little support, it could be used for training or carrying out daily tasks at home. This would hugely benefit the SCI community.

Study details

In this study, we will explore the success of spinal stimulation using surface electrodes to assist standing after spinal cord injury.

We hope to discover whether spinal stimulation enables people with spinal cord injury to stand, and whether regular sit-to-stand training plus spinal stimulation improves: 1) standing ability, 2) bladder control, 3) well-being.

Ten volunteers with spinal-cord injury will carry out an 8-week sit-to-stand training programme. Training will be carried out three times per week at Neurokinex using their Keiser Power Rack.

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The volunteers will be randomly assigned either to the control or test group. The control group will not receive any spinal stimulation during training, while the test group will receive spinal stimulation during each sit-to-stand and during standing.

Measurements will be taken before and after the training programme to assess their ability to stand up both with and without spinal stimulation and their bladder function using a standard clinical assessment. We will also use a questionnaire and a diary and monitor well-being using two questionnaires.