Exploring electrotherapy of denervated muscle

We recently had a vist from Dr Modlin from Vienna who was able to share her experience of using electrotherapy to restore denervated muscle.  She has some 15 years experience in this area which is probably pretty unique world wide.   We have now had a few months working with clients with the Stimulette den2x product, which can be used to restore muscle quality and bulk in denervated muscle. We wanted to short circuit the learning curve a bit and get to learn from a rare expert. 

One of the things that we learned pretty quickly is that the protocols described in the clinical papers are not exactly in line with those used in Dr Modlin's daily practice.  It's not that these are wrong - its just that useful nuggets of information are left out.  Sometimes these subtleties can make a big difference to results.

Lesions that cause denervation are those due to injury to the so called lower motor neuron. This might be due to a peripheral nerve lesion, brachial plexus injury or spinal cord injury at typically T12 or below. Such injuries cause rapid nerve degeneration followed by a cascade of other effects to the detriment of muscle tissue.

With spinal cord injuries, those with so called upper motor neuron lesions can, for example, use "conventional" FES systems.  In these cases, relatively small amounts of electrical energy can be used to trigger stimulation of a leg muscle via the intact nerve structures. 

Those with lower motor neuron damage find that such conventional FES techniques don't work.  The new Stimulette den2x actually aims to directly stimulate the muscle.  The levels and patterns of energy required are significantly different from those normally thought of with FES and protocols, electrodes and approches to use are all very different.

For many years, clinical and research work in Austria has focused on whether electrotherapy can be used to restore denervated muscle.  This idea has been controversial over the years but recent studies have been very positive - for example the RISE multicentre European trial was very successful in rescuing even long-term denervated muscles.  This is quite an important finding if it can promote improved tissue quality and circulation, as well as lower the risk of pressure sores.  Even when there is little or no expectation of reinnervation, preservation of muscle mass and improvement of the trophic situation is very important.

The RISE trial featured home-based training, 6 days per week and care needed to be taken during stimulation due to the energy levels used. 

Ideally with our clients we will work with quadriceps, hamstrings, gluteals and perhaps tibialis anterior and gastrocnemius/soleus, although the emphasis may change with the needs of the individual.

There are two dominant stimulation modes that we might use.  We are pretty much always using biphasic rectangular impulses. The pulse shape may on rare occasions be changed if a client has some sensation and it has been difficult to manage comfort levels.

If possible we want to stimulate a muscle group for approx 30 minutes per day - this is achieved gradually. For the first 3-4 weeks increasing the intensity and duration gradually is in order. The level of stimulation current is also carefully limited.

Stimulation is setup in programmes in the den2x so that the client can access them with a button press. Programmes are set for tetanic and twitch muscle contraction and both would typically be part of a programme.

If tetanic (smooth strong) contaction can be achieved this would be the primary focus of training with stimulation parameters something like this

40 ms impulse duration
20 ms impulse pause
3 secs surge duration (burst of pulses is on)
2 secs surge interval (burst of pulses is off)

With many clients, tetanic contraction is not easily achieved at the beginning and the stimulation is based on seeking "twitch" activation of the muscles.

120 ms impulse duration
400 ms impulse pause
5secs surge duration
2 secs surge interval

Once tetanic contraction is achievable, the aim is to develop muscle hypertrophy by working against a load.

This clearly requires a commitment from the client to work consitently with the programme and this has been one of my primary concerns about the techique. Would clients really be motivated to use the system especially if it took quite a while to see the benefits. So far early signs have been good.

According to research, there is a "window of opportunity" in using this technique.  Starting to use electrotherapy early is likely to preserve muscle tissue - a much better prospect than restoration in long standing denervated clients.

My feeling is that this technique has real value for certain clients with denervated muscles.  What would be ideal is if these persons could start to use electrotherapy early in their rehabilitation - in our case in the UK, whilst they are in the spinal units and then continue to use the system when they go hom