Peripheral Nerve Injury and Electrical Stimulation: Which of Three Situations Are You In?

It is a phone call I take regularly.

Someone has damaged a nerve. Perhaps a fracture, perhaps a fall, perhaps a complication of surgery they were told would be routine. They have read that electrical stimulation can help prevent muscle wasting. They have bought a device, often an inexpensive TENS unit, sometimes a consumer muscle stimulator. They have put the pads on, turned the intensity up as far as it will go, and nothing has happened. No contraction. No twitch. Nothing at all.

Then, usually near the end of the call, comes the question, and it is nearly always some version of this:

Could I have made it worse?

I want to answer that question properly, because it deserves better than the broad reassurance most websites offer. Then I want to give you something more useful than a yes or a no about whether electrical stimulation works for nerve injury. The truthful answer to that broader question is that it depends entirely on which of three situations you are in, and almost nobody explains how to find out which one is relevant to you.

"Could I have made it worse?"

If you have worried about this, you are not being irrational, and you have not been reading rubbish on the internet. You have arrived independently at a concern that occupied this field for decades.

When I first started working with electrical stimulation in the 1970s, my instructors warned me about exactly this in situations where muscle might be denervated due to injury to a nerve. The energy levels needed to make a denervated muscle contract were high. There were legitimate questions about skin burns. And underneath the practical worries sat a more fundamental one: if you artificially activate a muscle while its nerve is trying to grow back, might you interfere with that process? Might the muscle, kept busy by an external signal, be less receptive to the nerve when it finally arrived?

Nobody knew. The concern was strong enough that stimulating denervated muscle was viewed across much of the United Kingdom as promising but controversial, and it was genuinely difficult to find anyone who advocated it clinically.

So when you ask me whether you might have done harm, I do not dismiss it. It was, for a long time, an open question that serious people took seriously.

What the evidence says now

In 1996, Eberstein and Eberstein published a paper with a blunt title: "Electrical stimulation of denervated muscle: is it worthwhile?" They set out specifically to address the widespread belief that stimulation would prevent reinnervation.

Their conclusion was that electrical stimulation can preserve or restore the properties of denervated muscle, that appropriate stimulation parameters are critical to achieving this, and that it does not impede reinnervation. The best results came when the stimulation pattern resembled the firing pattern of a normal motor neuron.

Work since then has pointed the same way. Animal studies have shown stimulation after a crush injury preserving muscle mass and contractile strength without inhibiting recovery. Willand and colleagues, working in a rat model, found daily stimulation after nerve repair more than doubled the number of reinnervated motor units within two weeks, reduced unhelpful terminal sprouting, and increased growth factor levels in the muscle, with no negative effect on regeneration. The Vienna groups led by Helmut Kern, whose decades of work underpin much of what we now do clinically with denervated muscle, reached the same position: stimulation does not interfere with reinnervation, and may support it.

That is a reassuring body of evidence, and I think it justifies the way we work. But I am not going to present it as more settled than it is, because there are two things you should know.

The first is that much of this evidence comes from animal studies, and there is still no human randomised controlled trial addressing the specific situation many readers of this article are in: using stimulation while waiting for a nerve to regrow. The rationale for that use is extrapolated from research on permanent denervation. It is well founded, but it is not the same thing as direct proof.

The second matters more for your daily practice, and it runs against every instinct you have. More stimulation is not necessarily better. In the research on stimulation delivered around nerve surgery, extending treatment from one hour to two weeks did not improve results, and for sensory nerve fibres it was actively worse. There is also published work noting that in some circumstances stimulation has been observed to aggravate muscle fibre wasting and reduce muscle excitability. That finding sits alongside the reassuring evidence, not instead of it, and anyone quoting the reassuring half without the other half is not giving you the full picture.

KEY POINT: The worry that stimulation might interfere with nerve recovery was a serious scientific question for decades, and the weight of evidence has largely settled it: appropriate stimulation does not impede reinnervation and may assist it. But the word doing the work in that sentence is appropriate. The dose and the type matter, and more is not automatically better. If you turned a TENS unit up as high as it would go and nothing happened, you have almost certainly done no harm, because nothing was happening at all.

The question underneath the question

Here is the part that most pages about nerve injury and electrical stimulation get wrong.

They ask "does electrical stimulation help nerve damage?" and then the answer given might be yes, or occasionally no. Neither answer is absolutely true, because the question is incomplete.

Electrical stimulation is not "one thing", and nerve injury is not one thing.

What actually determines whether stimulation can do anything for you is a single question: is there a working nerve between your spinal cord and your muscle?

There are three possible answers, and they lead to three completely different places. Working out which one applies to you is the most useful thing you can do, and it is worth more than any amount of reading about devices. Once we understand the fidelity of the nerve structure in a specific case, we can understand which type of electrical stimulation can be beneficial.

Situation one: the nerve works, but the signal from the brain does not

This is the situation most of the information online is actually about, which is why it causes so much confusion. Let us consider a common scenario.

After a stroke, or in multiple sclerosis, or with an incomplete spinal cord injury, the damage is in the brain or the spinal cord. The nerve running from the spinal cord down the leg to the muscle is perfectly intact. What has been lost is the command travelling from the brain to that nerve.

This is the situation so-called foot drop stimulators were designed for. They work by electrically firing the common peroneal nerve at the right moment in your walking cycle, so the foot lifts and clears the ground. They are replacing a missing instruction from the controlling brain, not acting as a missing nerve.

This distinction is not a technicality I am inventing. It is written into the UK's national guidance. The NICE guidance covering these devices is titled "Functional electrical stimulation for drop foot of central neurological origin", and it states that the treatment is used for the effects of upper motor neurone lesions, arising from conditions such as stroke, cerebral palsy, multiple sclerosis or spinal cord injury. The MS Trust puts the requirement in plainer language: the nerve fibres between your spinal cord and your muscles must not be damaged, because the device stimulates the existing nerves in your legs.

If your foot drop came from a peroneal nerve injury at the knee, a hip or knee replacement, a fracture, or lumbar surgery, this is probably not your situation. And that matters, because you may have spent weeks reading about devices that cannot help you.

One more point, in the interests of not overselling something (even to the people it does suit). A meta-analysis by Prenton and colleagues found that functional electrical stimulation and ankle-foot orthoses produce equivalent therapeutic effects on foot drop. The stimulator is not automatically better than a brace for walking. Its advantages lie elsewhere: no bulk inside the shoe, the muscle is actively working rather than being held, and many people simply prefer it. Recent work also suggests the real gains accrue over a year of use rather than over a few weeks, which is worth knowing before you judge it too early.

KEY POINT: Foot drop stimulators require an intact nerve between your spinal cord and your muscle. They replace a missing command from the brain. If your nerve itself is the thing that was damaged, these devices may do little or nothing for you, whatever the marketing suggests.

Situation two: the nerve is partly damaged, and some of it still works

This is where many people with a peripheral nerve injury actually are, and it is the situation least well served by anything written online.

Real nerve injuries are rarely all or nothing. A nerve is a bundle of thousands of fibres, and an injury usually damages some and spares others. You may have a muscle where part of it still receives a signal and part of it does not. You may have obvious weakness alongside a flicker of movement that tells you something survived.

Where enough of the nerve pathway remains, conventional neuromuscular electrical stimulation (NMES) can produce a contraction, because there is still a nerve there to excite. Used sensibly, it can help maintain some muscle bulk and tissue quality while you wait for regeneration, and keep the muscle in a state where it can make use of the nerve when it arrives. With our clients, we would try to stimulate both the denervated and the preserved innervated component whenever possible.

I want to be measured about the strength of this evidence. The research reviewing stimulation for peripheral nerve injury describes a mechanism that makes sense: reduced wasting, maintenance of the receptors at the junction between nerve and muscle, and preservation of muscle protein. The same reviews caution that not all clinical applications have proved effective, that some studies have shown no improvement in muscle mass, and that after roughly a century of experimentation there is still no consensus on the ideal parameters, largely because studies have varied so widely that they cannot sensibly be compared.

So the position I take with clients is this. Where the lower motor neuron is partly intact, stimulation is a reasonable holding action with a sound mechanism behind it. It is not a cure, and it is not a substitute for the nerve regrowing. It is a way of making sure that when the nerve does arrive, there is still something worth arriving at. I have written about this elsewhere as a race between two entities: nerve regeneration versus muscle deterioration. Muscle fibre structure is steadily deteriorating in cases of denervation, and correctly applied stimulation can preserve that muscle structure whilst nerve recovery takes place.

Situation three: the nerve is completely interrupted

If the nerve supply to a muscle has been entirely lost, that muscle is denervated, and everything changes.

There is no nerve left to excite. So a conventional stimulator, which works by triggering a nerve and letting the nerve generate a muscle contraction, has nothing to trigger. This is not a weak result or a matter of finding better settings. It is nothing at all.

Muscle fibres can still be made to contract, but only by delivering enough electrical energy to depolarise the muscle fibre membrane directly, bypassing the nervous system entirely. The thresholds for doing this are roughly a thousand times higher than for stimulating a nerve. In practice that means very long pulses and much larger electrodes. We deal with a number of specialised products that support complete denervation, such as the KT-Parese or KT-Motion, the RISE or Edition 5 devices from Schuhfried.

Here is the comparison that explains why the device you bought did nothing:

	TENS	NMES / EMS	FES	Denervated muscle stimulation
What it targets	Sensory nerves	Motor nerves	Motor nerves	Muscle fibres directly
Purpose	Pain relief	Strengthening	Functional movement	Tissue preservation
Needs an intact nerve?	Yes (sensory)	Yes (motor)	Yes (motor)	No
Typical pulse width	50 to 400 microseconds	100 to 500 microseconds	100 to 500 microseconds	100 to 200 milliseconds
Typical current	Under 80 mA	10 to 130 mA	10 to 130 mA	Up to 250 mA
Will a "standard" device work?	Yes	Yes	Yes	No, specialised equipment required

Look at the pulse width row. Denervated muscle needs pulses hundreds of times longer than a standard device produces. Most stimulators are limited by design and by medical device regulation to pulse widths under one millisecond and currents under 130 mA. They physically cannot generate what denervated muscle requires. It is not a simple settings adjustment; it is fundamental, in the way that a petrol engine does not run on diesel.

This is also why the higher energies involved deserve respect. The recent narrative review by Chu and colleagues names the trade-offs directly: discomfort, poor selectivity because of the large electrodes needed, and a risk of skin burns and tissue damage with prolonged output. This is the one place where the "could I make it worse?" question has a practical answer, and it is about the correct technique and equipment rather than about the principle.

KEY POINT: If your muscle is completely denervated, a shop-bought TENS, EMS or NMES device will produce no contraction whatsoever, no matter how high you turn it. That is not evidence that stimulation cannot help you. You simply have the wrong tool.

How you find out which situation you are in

We described three situations above and you need to understand which situation applies to you. You cannot work this out by looking at your leg, and neither can I. It requires testing.

Nerve conduction studies and EMG are the main tools. Nerve conduction studies measure how well signals travel along the nerve, and EMG samples the muscle itself for the electrical signature of a muscle that has lost its nerve supply. Between them, they can tell you whether the nerve is bruised or interrupted, roughly how much of it survives, and whether reinnervation has started. I have written a full article on how to read your own report, which I would rather point you to than repeat here.

One thing worth knowing about timing: these tests need the injury to have declared itself. The changes EMG looks for take some weeks to appear, which is why a test done too early can be misleading, and why a repeat test after a few months is often more informative than the first one.

MRI, and specifically MR neurography, has a genuine and complementary role. Where nerve conduction studies tell you how the nerve is functioning, MR neurography shows you the nerve itself: where it is compressed, where it is trapped, and whether it has been disrupted. It has two advantages worth raising with your consultant. It can be performed within hours or days of an injury, well before electrical testing becomes informative. And modern techniques for reducing metal artefact mean it can often produce a useful image even when there is orthopaedic hardware in place, which matters a great deal if your nerve problem followed a joint replacement or a fracture fixation.

The two approaches answer different questions. Electrical testing tells you how much nerve is working. Imaging tells you where the problem is and what is causing it. For a surgical decision, you often want both.

"It has been six months and nothing has changed"

I hear this constantly, and it is usually said by someone who has quietly concluded that their recovery is over.

Very often, they are simply measuring recovery against an imaginary schedule nobody gave them. We humans are very good at worrying about problems we do not actually have.

Nerve injuries are traditionally described in three grades or classifications. The gentlest is a nerve that has been bruised or compressed: the insulation is disrupted, but the fibre inside is intact. Nothing has to regrow, and recovery typically takes days to about six weeks. The middle grade is where the fibres inside have been severed, but the surrounding tubes of connective tissue have survived. The fibre below the injury dies back, and a new one grows down the preserved tube. The most severe is a nerve divided completely, structure and all, where spontaneous recovery is not possible, and surgical repair is required.

You have probably encountered the figure of one millimetre per day for regrowth. It applies to the middle grade, and it comes with four caveats that might not have been explained.

First, the clock does not start on the day of your injury. The old fibre below the injury has to be cleared away first, and that takes roughly three to four weeks before regrowth properly begins.

Second, it is an average within a range. Published figures span roughly one to three millimetres per day, and progress is slower with your age, slower after a crush than a clean cut, and slower over long distances.

Third, fibres arriving is not the same as function returning. The fibre has to reach the right target, re-establish its connection, and rebuild its insulation. Misdirected regrowth is common.

Fourth, there is a deadline at the other end, which I will come to.

Let me make this concrete, because the arithmetic is more reassuring. If your nerve was injured at the knee and the muscle it supplies is in the lower leg, they are roughly 30 centimetres apart. At one millimetre per day, that is around 300 days. Add three to four weeks before the clock starts, and you are looking at something in the region of eleven months before you would expect to see anything at all at the target.

If you are four months in and despairing, you may be despairing about being exactly where you should be.

Now the deadline. Waiting is not neutral, and I would be doing you no favours by pretending otherwise. The support cells that guide a regrowing fibre down its tube deteriorate over time, and beyond roughly twelve weeks of denervation this begins to measurably reduce the eventual result. The connection points on the muscle itself remain receptive for a window usually given as twelve to eighteen months, after which arriving fibres may find little they can use. There is also evidence that stimulation delivered around nerve surgery becomes progressively less effective the longer the repair is delayed.

KEY POINT: The one millimetre per day figure is not a guaranteed delivery date. Add three to four weeks before the clock starts, and calculate the actual distance from your injury to the muscle. Many people conclude they have failed to recover when they have simply not waited long enough yet. That said, the window is real, and it is a good reason to get properly assessed sooner rather than later, rather than to wait passively for a date in the future.

What about the numbness?

Almost everything written about nerve injury and stimulation concerns movement and muscle. If your main problem is a hand that feels dead, you may have found very little to help.

Let us consider where the evidence sits. There is good research showing that sensory recovery can be improved by electrical stimulation, and it is genuinely good research: Wong and colleagues ran a double-blinded, sham-controlled randomised trial in patients whose finger nerves had been completely severed and surgically repaired, and found consistently better results across two-point discrimination, pressure thresholds and temperature sensation.

But that treatment was one hour of stimulation delivered by the surgeon, in theatre, with electrodes placed on the nerve. It is not something you can buy and do at home.

I am not aware of evidence that any home device restores sensation in a numb hand or foot. TENS is cleared for pain relief and related uses, not for nerve regeneration, and claims to the contrary have attracted regulatory action. If a product is being sold to you on the promise of bringing feeling back, treat that promise with suspicion.

What does deserve your attention in the meantime is protection. A hand or foot that cannot feel is a hand or foot that cannot warn you of hazards. Burns from hot water, taps, radiators and cooking, cuts you do not notice, and pressure damage from footwear are all genuinely common and entirely preventable. This is unglamorous advice, but it prevents more harm than any device I could sell you.

The thing almost nobody in the UK knows to ask about

If you are facing nerve surgery, or have recently had it, there is one question worth raising with your surgeon.

There is now a substantial body of human trial evidence, not animal evidence, that a single one hour treatment of electrical stimulation at 20 Hz, delivered to the nerve at the time of surgery, improves recovery. Gordon and colleagues showed improved reinnervation after carpal tunnel release in 2010, although notably without a matching improvement in symptoms. Wong and colleagues showed the sensory benefit described above in 2015. Power and colleagues, in a double blind randomised trial in severe cubital tunnel syndrome, found roughly double the number of restored nerve-to-muscle connections at three years, along with better grip strength. And a 2026 trial by Osaki and colleagues tried it the other way round, delivering the same hour of stimulation seven days before carpal tunnel surgery rather than during it, and found improvements in sensation and hand dexterity at twelve months.

The mechanism is interesting and often misdescribed. Stimulation does not make fibres grow faster. What it does is bring them together across the repair site promptly, instead of dribbling across over weeks, and it improves the accuracy with which they find the right targets.

This is not standard NHS practice, and I am not suggesting you demand it. But it is a reasonable thing to have heard of, and a reasonable thing to ask about, and I suspect that very few patients in the United Kingdom know it exists.

What I would suggest

If you take nothing else from this, take the central question: is there a working nerve between your spinal cord and your muscle? Everything else follows from the answer.

Some practical steps, all of which involve your own clinical team rather than us:

• Ask for a copy of your nerve conduction study and EMG report, and ask someone to talk you through what it shows about how much nerve has survived. If you have not had one, ask whether the timing is now right.
• Ask whether MR neurography would add anything in your case, particularly if there is metalwork in place or if the site of the problem is uncertain.
• Do the distance calculation for your own injury before concluding that recovery has stalled.
• If surgery is being planned or has recently happened, ask about electrical stimulation delivered at the time of the operation.
• If you have numbness, put protective habits in place now: check water temperatures with an unaffected limb, inspect the skin daily, and be careful with heat.

At Anatomical Concepts, our role is to help people get the most out of the right rehabilitation technology, assessed and specified for the individual rather than simply providing a product sold off the shelf. In this area, that often means telling someone that the device they were about to buy will do nothing for them, which is a conversation I would much rather have before the purchase than after.

Decisions about your treatment belong with your clinicians. What we can do is help you understand what the findings mean for the equipment question, and why. If you would like to talk it through, we are glad to do that.

Further reading

• Eberstein A, Eberstein S. Electrical stimulation of denervated muscle: is it worthwhile? Medicine and Science in Sports and Exercise. 1996;28(12):1463-1469. https://journals.lww.com/acsm-msse/Fulltext/1996/12000/Electrical_stimulation_of_denervated_muscle__is_it.4.aspx
• Chu L, Jarvis JC, Andrews BJ, FitzGerald JJ. Electrical stimulation of denervated muscle: a narrative review. Artificial Organs. 2026;50(4):493-504. https://doi.org/10.1111/aor.70076
• Ni L, Yao Z, Zhao Y, et al. Electrical stimulation therapy for peripheral nerve injury. Frontiers in Neurology. 2023;14:1081458. https://doi.org/10.3389/fneur.2023.1081458
• Wong JN, Olson JL, Morhart MJ, Chan KM. Electrical stimulation enhances sensory recovery: a randomized controlled trial. Annals of Neurology. 2015;77(6):996-1006. https://doi.org/10.1002/ana.24397
• Power HA, Morhart MJ, Olson JL, Chan KM. Postsurgical electrical stimulation enhances recovery following surgery for severe cubital tunnel syndrome: a double-blind randomized controlled trial. Neurosurgery. 2020;86(6):769-777. https://doi.org/10.1093/neuros/nyz322
• Osaki Y, Olson JL, Morhart MJ, et al. Conditioning electrical stimulation for patients with moderate or severe carpal tunnel syndrome: double blinded randomized controlled trial. Annals of Neurology. 2026;99(5):1251-1262. https://doi.org/10.1002/ana.78155
• Hardy PB, Wang BY, Chan KM, Webber CA, Senger JLB. Investigating the mechanism of conditioning versus postoperative electrical stimulation to enhance nerve regeneration: one therapy, two distinct effects. Muscle and Nerve. 2025;72(1):15-33. https://doi.org/10.1002/mus.28385
• Bleichner N, Alimusaj M, Heitzmann DWW, et al. Functional electrical stimulation in adults with neurological disorders and foot drop: orthotic and therapeutic effects in short and long term users. Bioengineering. 2026;13(1):71. https://doi.org/10.3390/bioengineering13010071
• National Institute for Health and Care Excellence. Functional electrical stimulation for drop foot of central neurological origin. IPG278, January 2009, now HealthTech guidance HTG178. https://www.nice.org.uk/guidance/ipg278

Related articles on our site

• What a Nerve Conduction Study Actually Tells You, and Why It Matters Before Electrical Stimulation
• Normal Versus Denervated Muscle: Why the Rules of Electrical Stimulation Change After Nerve Injury
• Electrical Stimulation After Nerve Repair Surgery: When to Start and What to Expect
• Can I Start Electrical Stimulation Years After My Denervation Injury?
• Why Your NMES Product Probably Doesn't Work With Denervated Muscle