Can I Start Electrical Stimulation Years After My Denervation Injury? What the Research Shows

12 Feb

One of the most common questions I receive comes from people who've had a denervating injury—whether spinal cord injury, brachial plexus injury, or another peripheral nerve condition—years or even decades ago. They've recently learned that electrical stimulation might help preserve or improve their muscle condition, and they want to know: Is it too late for me?

This is an important question that deserves a thorough answer. The research evidence and my clinical experience both suggest that while earlier is definitely better, "too late" is rarely the correct conclusion. In this article, I'll examine what the evidence actually shows about late intervention, which factors influence outcomes, and how to decide whether it's worth trying in your specific situation.

In this article, we don't discuss the technical aspects of stimulation. This has been covered in other articles on this site. Recognise, however, that the stimulation patterns are designed to work directly with the muscle fibre and do not rely on an intact peripheral nerve.

The Ideal: Starting Early

Let me begin by acknowledging what the research clearly demonstrates: outcomes are best when electrical stimulation begins soon after a denervating injury.

The European RISE study and subsequent Vienna research established that starting home-based stimulation within the first 1-2 years produces the most impressive results [1,2]. During this window:

- Muscle fibres remain largely intact despite early atrophy

- The internal structure of the muscle (myofibrils, T-tubules, sarcoplasmic reticulum) is still organised

- Fat infiltration and fibrosis are limited

- The muscle retains good capacity for recovery

The landmark 2010 study by Kern and colleagues followed 25 patients with complete conus/cauda equina lesions through two years of home-based functional electrical stimulation [1]. The results were remarkable:

- Quadriceps cross-sectional area increased by 35% (from 28.2 cm² to 38.1 cm²)

- Knee torque force improved by 1,187% (from 0.8 Nm to 10.3 Nm)

- Muscle fibre diameter increased by 75%

- 25% of participants achieved FES-assisted standing

If you're reading this within the first year or two of your injury, the message is clear: don't wait. Start exploring your options now.

KEY POINT: The first 1-2 years represent the optimal window for intervention. If you're in this window, act sooner rather than later.

The Reality: Many People Miss the Early Window

The ideal scenario isn't everyone's reality. Many people only learn about denervated muscle stimulation years after their injury. There are several reasons for this:

Limited awareness among healthcare providers: Despite decades of research, many clinicians remain unaware that effective treatment exists for denervated muscle. Some still hold outdated views that nothing can be done. Things have changed a lot in recent years, and not everyone is up to date with the literature.

Neutral guidance from spinal units: Clinicians in spinal injury centres sometimes remain neutral about specific products or approaches, leaving patients to navigate options on their own.

Focus on acute rehabilitation: In the immediate aftermath of injury, there's so much to deal with—adjusting to disability, learning new skills, managing medical complications—that long-term muscle preservation may not be a priority.

Information gaps: People simply don't know what they don't know. If no one tells you that electrical stimulation for denervated muscle exists and requires specialised equipment, you have no reason to seek it out.

Whatever the reason, if you're now 3, 5, 10, or more years post-injury and just learning about this option, you're not alone. The question is: what can still be achieved?

What Happens to Muscle Over Years of Denervation

To understand what's possible with late intervention, we need to understand what happens to denervated muscle over time. Research using muscle biopsies and electron microscopy has documented these changes in detail [3,4].

First 1-2 years:

- Muscle fibres atrophy (shrink) but remain largely intact

- Basic muscle structure preserved

- Myofibrillar alignment begins to deteriorate after 2-7 months [3]

- T-tubule system changes appear after approximately 4 months

- Good potential for recovery with stimulation

Years 2-5:

- Continued atrophy—muscle can lose 80-90% of its original mass [4]

- Progressive fat infiltration begins, visible on MRI as increased signal on T1-weighted images [5]

- Fibrosis (scar tissue) develops

- Muscle structure becomes less organised

- Recovery potential reduced but still significant

Beyond 5 years:

- Severe atrophy in many cases

- Extensive fat replacement of muscle tissue is possible

- Significant fibrosis

- Loss of normal muscle architecture

- Recovery potential is more limited but not necessarily absent

KEY POINT: Muscle changes after denervation are progressive but not instantaneous. Even years after injury, some viable muscle tissue often remains.

The rate of deterioration varies between individuals and depends on factors including:

The completeness of denervation
Individual metabolic factors
Activity levels and general health
Whether any partial innervation or reinnervation has occurred

A Crucial Finding: Satellite Cells Survive Decades of Denervation

Perhaps the most encouraging finding for people considering late intervention comes from recent research on satellite cells—the stem cells responsible for muscle regeneration.

A 2021 study by Wong and colleagues made a remarkable discovery: Satellite cells remain viable even after more than 20 years of denervation [6]. The researchers isolated muscle stem cells from the gluteus maximus of patients with complete spinal cord injuries sustained two decades earlier. These cells, when transplanted, successfully formed new muscle fibres.

The study concluded that "even after prolonged denervation, [muscle satellite cells] retain intrinsic regenerative potential similar to that of uninjured [satellite cells]" [6]. The problem isn't that the regenerative cells die off—it's that the muscle environment changes in ways that make regeneration more difficult.

This finding provides a biological rationale for attempting late intervention: the cellular machinery for muscle recovery may still be present, even many years after injury.

What the Research Shows About Late Intervention

The research specifically examining late intervention is more limited than that for early intervention, but several important findings emerge:

Chronic denervation (3-5 years) can still respond to Electrical Stimulation

Studies from the Vienna group showed that patients starting stimulation years after injury could still achieve improvements, though the timeline was extended. A case study published in 2005 documented a patient who began stimulation 18 months post-injury [7]. After 26 months of treatment:

- Right quadriceps cross-sectional area increased from 36.0 cm² to 57.9 cm² (+61%)

- Left quadriceps increased from 36.1 cm² to 52.4 cm² (+45%)

- Knee torque became sufficient to maintain standing without upper extremity support

- Muscle biopsies confirmed both growth and regeneration of muscle fibres

Progress is slower but real:

The Vienna group's longitudinal work confirmed that treatment initiated more than 5 years post-injury produces better outcomes than treatment initiated after 6 years [8]. However, "better outcomes with early treatment" doesn't mean "no outcomes with late treatment."

Tissue quality can improve even when mass gains are modest:

Some chronic cases showed improvements in tissue characteristics—reduced fibrosis, better organisation of muscle fibres—even when increases in bulk were limited [3]. This still contributes to better long-term health outcomes.

Very long-term denervation (>5 years) is less systematically studied:

There's less rigorous research on outcomes for people starting after 5+ years. However, the satellite cell research [6] and evidence of ongoing regenerative attempts in muscle biopsies taken up to 37 years post-injury [4] suggest that biological potential for response persists far longer than previously assumed.

Factors That Influence Late Intervention Success

If you're considering starting stimulation years after your injury, several factors help predict whether you're likely to benefit:

1. What Does Imaging Show?

If you've had CT or MRI scans of your affected muscles, the findings are informative. Radiologists often use the Goutallier classification to grade fatty infiltration [9]. Basically, fat cannot contract, no matter how much stimulation you provide. Therefore, the more muscle fibres that remain, the easier it is to generate muscle contractions.

Grade 0: No intramuscular fat
Grade 1: Some fatty streaks
Grade 2: Fat evident but less than muscle tissue
Grade 3: Fat equal to muscle
Grade 4: More fat than muscle

Research suggests that Grade 3 or higher (50% or more fat) represents a threshold beyond which recovery becomes significantly more challenging [10]. However, this doesn't mean recovery is impossible—it means expectations should be adjusted accordingly.

Preserved muscle tissue (even if atrophied): Good potential for response. The muscle fibres are still there, just diminished.

Moderate fat infiltration (Grades 1-2): Still worth trying. Viable muscle tissue likely remains among the fat.

Extensive fat replacement (Grades 3-4): More challenging. If imaging shows that the muscle has been substantially replaced by fat, the substrate for recovery is limited. However, imaging isn't always definitive, and some response may still be possible given the persistence of satellite cells [6].

2. Has Any Spontaneous Activity Been Observed?

If you've noticed any muscle twitches, even occasional ones, this suggests some muscle fibre viability. This is a positive sign for potential response to stimulation.

3. How Complete Is the Denervation?

Some injuries are not as complete as initially classified. If there's any possibility of partial innervation or slow reinnervation, the prospects improve. Peripheral nerve injuries, in particular, sometimes show late recovery.

4. What's Your General Health?

Conditions affecting tissue healing and metabolism (diabetes, poor circulation, nutritional deficiencies) may influence response. These don't preclude trying, but they're factors to consider.

5. Can You Commit to Extended Protocols?

Late intervention requires patience. If early starters might see clear progress in 3-6 months, you might need 12-24 months of consistent application before tetanic (sustained) contractions emerge [1,7]. Can you sustain that commitment? This is really important because electrical stimulation to rescue denervated muscle takes a commitment of five or six days a week and at least 30 minutes per muscle group.

The Risk-Benefit Calculation

When deciding whether to pursue denervated muscle stimulation years after injury, consider the risk-benefit calculation:

Risks of trying:

The RISE Stimulator from Schufried in Austria evolved from the stimulator used in the RISE research study

Financial investment in equipment such as the RISE Stimulator
Time investment in daily protocols
Possible disappointment if results are limited
Minor risks of skin irritation (manageable with proper technique)

Risks of not trying:

Accepting continued progressive muscle deterioration
Increasing risk of pressure ulcers over time
Worsening circulation in affected limbs
Missing potential for improvement that does exist

Potential benefits:

Research has documented several benefits beyond muscle mass preservation:

Improved circulation: Studies show electrical stimulation increases blood flow and tissue oxygen saturation in paralysed muscles by up to 100% during stimulation [11,12]

Pressure ulcer prevention: Reviews of FES‑based pressure‑management strategies generally report positive effects on interface pressure and tissue oxygenation in most included studies [13]

Better pressure distribution: Stimulation changes muscle shape, improving how pressure is distributed during sitting [11]

Metabolic benefits: Research shows improvements in body composition and cardiovascular performance indices [14]

Appearance: Many clients state the value they place on having normal-looking legs.

For most people, the potential benefits outweigh the risks. The worst case is that you invest time and money for a limited return. The best case is a meaningful improvement in tissue health and a reduced risk of complications. The middle ground—stabilisation rather than continued decline—is itself valuable.

KEY POINT: The risks of trying are relatively low. The risks of continued inaction include ongoing deterioration and increased complication risk. For most people, attempting late intervention makes sense.

What I Tell Clients Who Ask "Is It Too Late?"

When someone contacts me years after their injury asking if it's too late, here's my response:

It is always worth trying (assuming there are no contraindications to use)

The KT Range is one of our preferred systems for some clients with denervation

I don't promise specific outcomes. I can't guarantee you'll see the dramatic improvements demonstrated by the early-intervention research. Your results may be more modest, slower to appear, or, in some cases, limited.

The satellite cell research shows that regenerative potential persists even after 20+ years [6]. Unless imaging clearly shows complete fat replacement with no remaining muscle tissue, there's reason to believe some response is possible. The risks are low enough that an empirical trial makes sense.

I recommend a proper assessment. Before committing to equipment purchase and a demanding protocol, let's evaluate your specific situation. Testing muscle response to stimulation can give us useful information about viability.

Set realistic expectations. For someone 5+ years post-injury, I'm more likely to frame goals around stabilisation, tissue quality improvement, and health benefits (circulation, pressure ulcer prevention) rather than dramatic recovery. If we can halt continued deterioration and improve tissue quality, that's a meaningful success.

Acknowledge uncertainty. The research on very late intervention is limited compared to early intervention. You're somewhat in less-charted territory. I'll share what we know while being clear about what we don't.

A Framework for Deciding

If you're years post-injury and considering denervated muscle stimulation, here's a framework for thinking through your decision:

Strongly consider trying if:

- You're 2-5 years post-injury

- You have preserved muscle tissue (even if atrophied) on any available imaging

- You can commit to extended protocols (12-24 months minimum)

- You have realistic expectations about gradual, modest improvements

- Preventing future complications is a priority for you

Still consider trying if:

- You're more than 5 years post-injury

- Imaging status is unknown or shows moderate changes (Goutallier Grade 1-2)

- You understand outcomes are uncertain

- You can accept the possibility of a limited response

- The alternative (continued deterioration) is unappealing

Proceed with caution if:

- Imaging clearly shows extensive fat replacement (Goutallier Grade 3-4)

- You cannot sustain a long-term protocol commitment

- You have unrealistic expectations of rapid, dramatic recovery

- Financial constraints make equipment investment difficult

May not be appropriate if:

- Muscle tissue is confirmed absent (complete fat/fibrous replacement on multiple imaging modalities)

- Medical contraindications exist

- You're seeking a quick fix rather than long-term management

Making the Commitment

If you decide to proceed with late intervention, commit fully:

Expect a long timeline. Where early starters might see clear progress in 3-6 months, budget 12-24 months before drawing firm conclusions [7]. Stick with the protocol even when progress seems slow.

Document your baseline. Take measurements and, if helpful, photographs, and note your starting point. With slow progress, it's easy to forget where you started. Much easier to note your progress if you do this.

Regular review. Schedule periodic assessments (every 6 months) to objectively evaluate progress and adjust protocols if needed.

Stay consistent. The cumulative effect of hundreds of daily contractions over months and years is what produces results. Sporadic application won't work.

The Case for Optimism

Despite the caveats and my acknowledgements of uncertainty, I want to end on a note of appropriate optimism.

The science supports attempting late intervention. Satellite cells—the stem cells responsible for muscle regeneration—survive for decades after denervation [6]. Muscle biopsies show evidence of ongoing regenerative attempts even 37 years after injury [4]. Case studies document meaningful improvements in patients who started stimulation well after the "optimal" window [7]. This is a much more optimistic picture than the one a few decades ago.

I have worked with clients who started stimulation years after their injuries and achieved meaningful benefits. Not quite everyone, and not always dramatic, but enough to justify the approach for most people.

The fact that you've found your way to this information—even years late—puts you in a better position than continuing without intervention. The body has more regenerative capacity than we sometimes credit, and denervated muscle fibres can respond to appropriate stimulation even after extended periods of disuse.

If you're wondering whether it's too late, my answer is probably not. The only way to know for certain is to try.

Getting Started

If you'd like to explore whether denervated muscle stimulation might help your situation—regardless of how long ago your injury occurred—we're happy to discuss your circumstances. Two of our product lines are relevant: the RISE Stimulator and the KT range.

At Anatomical Concepts, we work with people at all stages post-injury. We can help you understand what's realistic for your situation, conduct an appropriate assessment, and guide you through establishing an effective protocol if you decide to proceed.

Please contact us if you have questions or would like to discuss your specific circumstances. There's no obligation, and a conversation about your options is always worthwhile. If you're working with a health care professional, we're more than happy for them to contact us on your behalf.

References

1. Kern H, Carraro U, Adami N, Biral D, Hofer C, Forstner C, Mödlin M, Vogelauer M, Pond A, Boncompagni S, Paolini C, Mayr W, Protasi F, Zampieri S. Home-based functional electrical stimulation rescues permanently denervated muscles in paraplegic patients with complete lower motor neuron lesion. *Neurorehabilitation and Neural Repair*. 2010;24(8):709-721. doi:10.1177/1545968310366129

2. Kern H, Carraro U. Home-based functional electrical stimulation for long-term denervated human muscle: History, basics, results and perspectives of the Vienna Rehabilitation Strategy. *European Journal of Translational Myology*. 2014;24(1):27-40. doi:10.4081/ejtm.2014.3296

3. Kern H, Boncompagni S, Rossini K, Mayr W, Fanò G, Zanin ME, Podhorska-Okolów M, Protasi F, Carraro U. Long-term denervation in humans causes degeneration of both contractile and excitation-contraction coupling apparatus, which is reversible by functional electrical stimulation (FES): a role for myofiber regeneration? *Journal of Neuropathology and Experimental Neurology*. 2004;63(9):919-931. doi:10.1093/jnen/63.9.919

4. Carraro U, Boncompagni S, Gobbo V, Rossini K, Zampieri S, Mosole S, Ravara B, Nori A, Stramare R, Ambrosio F, Piccione F, Masiero S, Vindigni V, Gargiulo P, Protasi F, Kern H, Pond A, Marcante A. Persistent muscle fiber regeneration in long term denervation. Past, present, future. *European Journal of Translational Myology*. 2015;25(2):4832. doi:10.4081/ejtm.2015.4832

5. Fleckenstein JL, Watumull D, Conner KE, Ezaki M, Greenlee RG Jr, Bryan WW, Chason DP, Parkey RW, Peshock RM, Purdy PD. Denervated human skeletal muscle: MR imaging evaluation. *Radiology*. 1993;187(1):213-218. doi:10.1148/radiology.187.1.8451416

6. Wong A, Garcia SM, Tamaki SJ, Striedinger K, Barruet E, Hansen SL, Young DM, Pomerantz JH. Satellite cell activation and retention of muscle regenerative potential after long-term denervation. *Stem Cells*. 2021;39(3):331-344. doi:10.1002/stem.3316

7. Kern H, Salmons S, Mayr W, Rossini K, Carraro U. Recovery of long-term denervated human muscles induced by electrical stimulation. *Muscle and Nerve*. 2005;31(1):98-101. doi:10.1002/mus.20149

8. Carraro U, Kern H, Gava P, Hofer C, Loefler S, Gargiulo P, Mosole S, Zampieri S, Gobbo V, Ravara B, Piccione F, Marcante A, Baba A, Schils S, Pond A, Gava F. Biology of muscle atrophy and of its recovery by FES in aging and mobility impairments: roots and by-products. *European Journal of Translational Myology*. 2015;25(3):221-230. doi:10.4081/ejtm.2015.5272

9. Goutallier D, Postel JM, Bernageau J, Lavau L, Voisin MC. Fatty muscle degeneration in cuff ruptures. Pre- and postoperative evaluation by CT scan. *Clinical Orthopaedics and Related Research*. 1994;(304):78-83.

10. Gibbons MC, Singh A, Anakwenze O, Cheng T, Pomerantz M, Schenk S, Engler AJ, Ward SR. Histological evidence of muscle degeneration in advanced human rotator cuff disease. *Journal of Bone and Joint Surgery (American)*. 2017;99(3):190-199. doi:10.2106/JBJS.16.00335

11. Smit CA, Legemate KJ, de Koning A, de Groot S, Stolwijk-Swüste JM, Janssen TW. Gluteal blood flow and oxygenation during electrical stimulation-induced muscle activation versus pressure relief movements in wheelchair users with a spinal cord injury. *Spinal Cord*. 2013;51(9):694-699. doi:10.1038/sc.2013.66

12. Gyawali S, Solis L, Chong SL, Curtis C, Bhatt S, Bhargava R. Intermittent electrical stimulation redistributes pressure and promotes tissue oxygenation in loaded muscles of individuals with spinal cord injury. *Journal of Applied Physiology*. 2011;110(1):246-255. doi:10.1152/japplphysiol.00661.2010

13. Dolbow DR, Gorgey AS, Recio AC, Stiens SA, Curry AC, Sadowsky CL, Gater DR, Martin R. Activity-based restorative therapies after spinal cord injury: inter-institutional conceptions and perceptions. *Aging and Disease*. 2015;6(4):254-261. doi:10.14336/AD.2014.1105

14. Gorgey AS, Khalil RE, Gill R, Gater DR, Lavis TD, Cardozo CP, Adler RA. Low-dose testosterone and evoked resistance exercise after spinal cord injury on cardio-metabolic risk factors: an open-label randomized clinical trial. *Journal of Neurotrauma*. 2019;36(18):2631-2645. doi:10.1089/neu.2018.6136

Can I Start Electrical Stimulation Years After My Denervation Injury? What the Research Shows

The Ideal: Starting Early

The Reality: Many People Miss the Early Window