Case study review: FES and Dystonia

Welcome back. Today’s blog we are going to discuss a case study by Barrett, Bressman, Levy, Fahn, & O’Dell (2011) titled ‘Electrical stimulation for the treatment of lower extremity dystonia’. This is an interesting case study of a 62 year old female (Mrs X) who initially presented with dystonic right side toe flexion and plantar flexion that occurred during walking. Mrs X condition was diagnosed as Focal Dystonia; she tried various treatments including an extensive exercise programs, Botulin injections, levodopa medication and an Ankle Foot Orthotic. All of the treatments listed provided no long term change to the dystonic muscles.

Mrs X was fitted with a closed loop (closed/open loops discussed in blog 2) radio frequency-controlled FES device (Type: NESS L300, Bio-ness Ltd) similar to those used for foot drop treatment (Foot drop discussed in blog 3). The surface electrode positioning was aimed at stimulation of the Peroneal nerve during the swing phase of the gait cycle. The goal of this was to induce dorsiflexion and inversion to oppose Mrs X dystonic contractions. Please view the picture attached at the bottom of this blog as an example of the FES devise used on Mrs X.

This case study showed some interesting results. After 18 months of FES usage, Mrs X showed an improvement in balance and endurance during functional reassessment while the FES device was attached and active. If the FES device was attached but deactivated or not worn at all, the improvements seen over the last 18 months were rapidly lost. Our interpretation of this case study makes a couple of interesting points. Firstly, having an FES device attached to you does not instigate a placebo effect of greater muscle control following long term use. Secondly, the success of FES when used in dystonia treatment potentially lies in masking the symptoms; not in actual retraining of the dystonic muscle. Not being able to rectify the dystonia does not mean this treatment has failed. Keep in mind that in this particular case study other treatment types were tried and failed to improve functional reassessment. We interpret this to mean the FES was successful but limited in its beneficial capacity when treating dystonia. Another point to consider is that in this case study the presentation was very similar to foot drop. We would be interested to see if you could apply FES for dystonia treatment to other lower limb muscles that are of greater muscle mass, e.g. quadriceps. If you are interested in reading more on this case study please view the hyperlink below:
http://www.sciencedirect.com/science/article/pii/S1353802011003142

I hope this post increased your knowledge base within the real of lower limb FES and as always, till next time, stay safe.

THe above picture is an example of the FES devise used on Mrs X.
http://www.mstrust.org.uk/professionals/information/wayahead/articles/06042002_03.jsp
 

Reference:

Barrett, M. J., Bressman, S. B., Levy, O. A., Fahn, S., & O’Dell, M. W. (2011). Functional electrical stimulation for the treatment of lower extremity dystonia. Parkinsonism & Related Disorders

FES for drop foot

Hello to everybody once again, this blog will focus on the pioneering uses of FES in drop foot after a person has had a stroke. The main focus of this blog will be assessing the suitability of foot switch FES in correcting the gait cycle.

           
The factors necessary for successful FES of the lower limb are: appropriate patient selection, comprehensive guided training, and effective follow-up after initial installation of the FES device (Embrey, Holtz, Alon, Brandsma, & McCoy, 2010). The FES device will be used to improve dorsiflexion during the swing phase and at primary contact and increase plantar flexion at toe-off (Embrey et al., 2010). The eccentric dorsiflexion contractions are essential for normal gait because it allows for shock absorption and to prevent foot slap (Popovic & Sinkjær, 2000). The video in the blog displays an FES device but it is not the device reviewed, the device that is reviewed is shown in the pictures below the video. The video has been inserted to demonstrate correction of foot drop via FES. Although, the device displayed in the video varies from the device reviewed in the study, they were both developed with the same functional outcomes as a priority. 

Equipment and parts

The FES device is administered via surface electrical stimulation electrodes (5.08 × 5.08 cm [2 ×2 in]) and they are applied to the ankle dorsiflexor muscles (Kesar, Perumal, Jancosko, Reisman, Rudolph, Higginson & Binder-Macleod, 2010). Accurate electrode placement is essential because it will limit the amount of ankle inversion and eversion during gait (Kesar et al., 2010). Two compression-closing footswitches (25-mm diameter MA-153) are attached bilaterally to the soles of each shoe, one on the forefoot under the fifth metatarsal head and the other on the hind foot under the lateral portion of the heel, they are used to control the timing of FES during gait (Kesar et al., 2010). These electrodes are connected to a Grass S8800 stimulation, in combination with a Grass Model SIU8TB stimulus isolation unit, which deliver the electrical stimulation (Kesar et al., 2010). The functional parameters for both items can be viewed via the hyperlinks.

How it all works  

Once the FES device has been tailored specifically to the participant, they are placed into a seated position which allows their foot to hang freely in a plantar-flexed position (Popovic & Sinkjær, 2000). The FES device stimulation amplitude is established by gradually increasing the amplitude of a 300-millisecond-long, 30-Hz train with a pulse duration of 300 microseconds until a neutral ankle joint position (0°) is gained (Popovic & Sinkjær, 2000). In severe control deficit cases, a plantar flexion of at least 5 degrees needs to be acquired from the FES device stimulation (Kesar et al., 2010). The FES device purpose is to supply the FES to the paretic (paralysis) ankle dorsiflexor muscles during the swing phase of each gait cycle and this is sensed by the footswitches placed on the foot. (i.e., from the time when the forefoot footswitch was off the ground to the time when the hindfoot footswitch contacts the ground)(Kesar et al., 2010).

3D animation of foot drop treated by FES (Please note this treatment varries slightly from that explained above)

Outcomes of the FES system

The benefits of this FES system are increased dorsiflexor of the paretic muscles of the ankle (Popovic & Sinkjær, 2000). This functional enhancement causes a reduction in ankle plantar flexion at toe-off and reduced knee flexion during the swing phase of gait (Popovic & Sinkjær, 2000). Although, there is an increased amount of ankle dorsiflexion from the FES system, there was no improvement in hip circumduction. The cause of the non-reduction in hip circumduction is because hip circumduction is used as a gait compensatory technique and this habit would not be immediately stopped when the person had regained necessary foot clearance during gait (Kesar et al., 2010).

The Cost

1 x Transformer Stimulus Isolation Unit, Transformer Coupled     £599.50

1 x Grass S8800 stimulator                                                              £60.50

Picture from : http://www.lowerextremityreview.com/article/next-step-for-fes-focuses-on-plantar-flexor-muscles

FES: Whats the Buzz

FES Buzzing on!

Picture 1: The informative text book of Faghri, Garstang, & Kida (2009).

For the information throughout out next blog, we would like to acknowledge Faghri, Garstang, & Kida (2009) for their very interesting book ‘Spinal Cord injuries: Management and Rehabilitation’. Chapter 17 of this book is entirely dedicated to FES and is written in an informative and interesting manner. For those wanting to learn more on this topic you can find an online or hard copy at the Griffith University Library. We have added a picture of the front cover for easy identification if you’re looking for it. Now let’s look at some detail of FES.

There are two basic areas of variability when it comes to FES application. Firstly, the parameters within the stimulation delivered and secondly, the variation of delivery method. The principle factors that that affect the muscular response to FES (Stimulation variables) include: the manipulation of the current via wave amplitude, frequency, pulse width and waveform manipulation. Table 2 outlines the key points to consider when setting stimulus parameters. The other important stimulation variable is the duty cycle. This is the ratio of 'on' time to the total cycle of stimulation which influences the fatigue rate of the muscle being stimulated. The patient’s tolerance to the electrical stimulation also needs to be considered when setting the parameters mentioned (Faghri, Garstang, & Kida, 2009).

Stimulation parameter	Overview
Waveform	A symmetrical biphasic AC current results in a good tetanic muscle response with minimal skin irritation
Amplitude	Direct effect on the sensory and motor unit response. The greater the amplitude the greater the motor unit recruitment.
Frequency	The rate of electrical pulses being delivered to the muscle stimulated therefore influences the temporal summation and rate of fatigue of muscle.
Pulse Width	Width of pulse needs to be enough to exceed excitability threshold of the motor neuron but functional considerations of fatigue are also important to consider.

Table 2: Key points to consider when setting stimulus parameters of FES (Faghri, Garstang, & Kida, 2009)

All powered up but how to make it go?

The second area of variability we mentioned earlier is how the user controls the delivery of FES. Table 3 outlines the various delivery methods via an open or closed loop electrical stimulation to the lower limb.

Parameter	Variables
Open loop	·         The most basic control type is the user controlled open loop system ·         Patient controlled delivery of a pre-set stimulation level regardless of the muscle feedback. ·         Open loop signals are not modified unless manually adjusted by the patient or therapist ·          Application of this would be a cyclical open loop system used to strengthen weak lower limb muscles
Closed Loop	This is a more complicated delivery of current that is firstly initiated by the user then modified on a feedback system that accounts for muscle fatigue and  the force of the required action Adjustment of current delivery can occur without the user knowing via sensor feedback located on the muscle of interest or the point force supplied by the muscle Application examples  of closed loop systems include gait motion retraining and chronic hemiplegia of the dorsiflexors

Table 3 This table shows a comparison between open and closed loop delivery of FSE(Faghri, Garstang, & Kida, 2009).

The final point on current delivery we would like to mention is the external or internal delivery of FES. External delivery FES is simple and involves electrodes placed directly on the skin. This is a nonspecific application and can potentially result in muscle activation and fatigue of non-target muscles (Elder & Spetzler, 2003). Internal electrodes are more specific to external as they can be planted directly into a muscle or adjacent to a specific nerve (Faghri, Garstang, & Kida, 2009). This allows for action potentials to be generated in the nerve that directly innervates the muscle of interest, or direct stimulation of excitation contraction within the muscle itself (Faghri, Garstang, & Kida, 2009), (Elder & Spetzler, 2003). The diagram 1 below highlights how external electrodes can be placed on the body for gait motion retraining.  

http://www.mpi-magdeburg.mpg.de/research/projects/1119/1133/1133GAIT/index.en.html?pp=1

But of course, with anything electrical, there is always some form of risk and contraindications that must be followed for the safe and effective use of FES. The absolute contraindications are: pacemakers, pregnancy, stimulation near the carotid sinus and over malignant tumours. As FES does produce muscle contractions other relative contraindications include: osteoporosis, contractures of limbs, hyper or hypotension and risks of venous thrombi. There are some other risks associated with FES including spacticity and burns risks. A complete list of these precautions can be found in Faghri, Garstang, & Kida (2009) text we discussed at the start of this blog.

This concludes our second posting of FES on the lower limb. So far we have outlined the basic principles for you that govern FES and how its is used on the lower limb. Over the next few blogs we aim to bring you some exciting detail on clinical applications of this amazing treatment.

Till then, stay safe.

References:

Elder, W., & Spetzler, R. F. (2003). Functional Electrical Stimulation (FES). Encyclopedia of the Neurological Sciences (pp. 401-403). New York: Academic Press.

Faghri, P. D., Garstang, S. V., & Kida, S. (2009). Functional Electrical Stimulation (pp. 407-429)