Denervated muscle and the Stimulette Den2x

Note: The Den2x has been updated - See more recent articles on the Stimulator RISE and it’s application with denervated muscle

When a spinal cord injury involves the so-called lower-motor neurons "conventional" FES does not work well or work at all. This type of injury causes a rapid loss of muscle mass in the lower limbs and the peripheral endings of affected motor neurons will degenerate. The muscle tissue changes it's structure over time and the person has a hightened risk of developing pressure sores. It would appear that the health giving benefits of activities like FES Cycling are not available to use. 

Stimulette Den2x system with Safety Electrodes

Programmable Keys make the system easy and safe to use for home use

In the 1990‘s, stimulating denervated muscle to restore it was seen as promising but controversial by some in the UK due to concerns about safety.  As mentioned above, the stimulation parameters utilised in conventional FES to promote muscle contraction do not work with denervated muscle. 

The process of conventional FES relies on the nervous system structure within a muscle and of course this is destroyed by the denervation.  Electrotherapy for denervated muscle relies on using the FES energy to make the muscle fibres contract directly using long duration pulses of relatively high energy.

During the EU Project RISE, a team of scientists and physicians from Austria, Germany, Italy, United Kingdom, Slovenia and Iceland, acquired essential insights into functional electrical stimulation (FES) of denervated muscles.  

RISE demonstrated that home-based FES of denervated muscle is an effective therapy that results in the rescue of muscle mass and restoration of tetanic contractility - even after many years of denervation.   This project and the subsequent product development, are founded on more than 20 years research in Austria.

We may use large conductive carbon and wet sponge electrodes

The stimulators and custom electrodes that evolved were required to deliver high-intensity and long duration impulses (much different from conventional FES applications) that can directly elicit contraction of denervated skeletal fibres in the absence of nerve endings. 

The product Stimulette den2x from the company Dr Schuhfried (Austria) embodies this development and includes especially developed electrodes to ensure safe and effective use.  Subsequent research has confirmed the positive results of the RISE project and extended them through a two year longitudinal study of 25 patients with complete conus/cauda equina lesions and up to 9 years of denervation.

These interesting studies also suggest that there is a prime “window of opportunity” up to 2 years post-injury to initiate stimulation and avoid the most severe muscle degeneration and infiltration.   This suggests that optimal deployment would occur when suitable users utilise this electro-therapy during their time within the spinal units and then continue this usage for the long term.

Suggested Direct and indirect benefits of stimulating denervated muscles:

• Recovery of muscle mass and fibre size

• Recovery of tetanic contractility

• Restoration of muscle fibre structure

• Enhanced cushioning effect for seating

• Better skin condition

• Reduced risk of pressure sores

• Improved cosmetic appearance of lower extremities

The product is simple to use but requires daily use (say 5 or 6 days per week). Once muscle quality and bulk has been restored then the usage can be reduced to say two or three times per week.

With our clients that have adopted the den2x we have noted significant gains in muscle mass - measured as mid thigh circumference increases of 3 to 7 cms after 6 months usage.  We expect this to result in reduced risk of pressure sore development.  Clients are typically pleased with the improved aesthetic appearance which is a factor sometimes overlooked by clinicians.  We have also used the Stimulette den2x to accelerate healing of pressure sores.

As an interesting observation we have had a number of clients who were intially classified as completely denervated who have been able to "graduate" to using FES Cycling systems.  Most likely they had some preserved function which the application of the Den2x has been able to bring out.  The ability to then use FES Cycling and conventional FES is important as it makes possible other forms of exercise essential for long-term health.

See our web page at this link for details of the RISE unit which has updated and replaced the Den2x

For an overview see the following article

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 Oct; 24(8): 709-721