What can I do to help denervated muscles?

Skeletal muscle denervation is caused by damage or injury to the nerves that supply a muscle. This can occur as a result of a number of different conditions, including trauma to the spine or a peripheral nerve.

Denervation can also result from infection, inflammation, and certain medical procedures. In some cases, denervated skeletal muscle may be caused by diseases that affect the nerves, such as amyotrophic lateral sclerosis (ALS) or Guillain-Barré syndrome. Denervation can also occur as a complication of surgery, such as when a nerve is accidentally damaged during an operation.

Muscles can recover from denervation, despite the loss of nerve supply to a muscle. Sometimes this recovery happens with little intervention necessary. At Anatomical Concepts we are typically working with individuals where some intervention is indicated.

What are the consequences of denervation?

When a muscle is denervated, it can become smaller and weaker (muscle atrophy) but with time and the right type of rehabilitation, the muscle can regain some or all of its strength and function. This process is known as muscle plasticity, and it involves the formation of new nerve connections to the muscle and the activation of dormant muscle fibers. Recovery from denervation can take several weeks or many months, depending on the severity of the nerve damage and the age and overall health of the individual. Denervation is often seen in older persons that are inactive and not using their muscles against resistance.

After denervation, muscle tissue experiences changes that are typically described in three stages:

1) immediate loss of voluntary function and rapid loss of mass,

2) increasing atrophy and loss of sarcomeric organization, and

3) muscle fiber degeneration and replacement of muscle by fibrous connective tissue and fat.

Parallel to the overall program of atrophy and degeneration is the proliferation and activation of satellite cells, and the appearance of new muscle fibers within the denervated muscle. Techniques such as functional electrical stimulation take advantage of this capability to restore functional mass to a denervated muscle.

Some years ago, the European RISE study demonstrated that muscle bulk and tissue quality of denervated muscle can be restored using a form of electrical stimulation. This study focused on cases of complete denervation following a spinal cord injury and used this technology in a home-based protocol.

Electrical Stimulation Approach

We use the protocols that arose originally from the RISE study with home-based clients with denervated muscle due to spinal cord injury, brachial plexus injuries or trauma. We do typically have to vary the stimulation parameters for optimal results.

In cases where reinnervation is expected, the use of electrical stimulation can assist in this by preserving muscle tissue quality during recovery. When reinnervation is not expected, the approach is still beneficial as it can reduce long-term complications by improving the trophic situation.

Two channel electrotherapy device

Helmut Kern and others have written in detail about the stimulation protocols to use.  We describe the early-use stimulation patterns as producing a “twitch contraction” as this is the effect noticed with the muscle. The stimulation waveform we use is typically a bipolar, rectangular pulse with low frequency and relatively long pulse widths of up to 200 ms. Such long pulse widths are necessary to excite the muscle fibers to contract directly. Many forms of FES use pulse widths of up to 500 microseconds, but these rely on activating an intact nerve structure - in these cases the nerve structure is compromised and we must elicit direct contraction of the muscle fibers. After some time, the muscle can be strengthened by using a protocol that produces a tetanic contraction in the muscles. In this case, the waveform is still bipolar, rectangular pulses of perhaps 40 ms with a frequency of around 20Hz.

In application, it may be necessary to use relatively high levels of current and the unit we use can generate up to 250 mA. Electrodes will consist of a conductive rubber electrode within a wet sponge case or a special type of safety electrode with gel.

With regular use, significant gains in muscle bulk and quality can be expected. Many clients appreciate the improved appearance of their limbs. This alone may be sufficient motivation to commit to electrotherapy but we can also expect a reduction in complications if they can stick with use.

In 2023, we will be offering a webinar covering electrotherapy for denervated muscle where we will discuss both the research and clinical practice aspects of this work