Functional electrical stimulation through direct 4-channel nerve stimulation to improve gait in multiple sclerosis: a feasibility study
Hausmann et al. Journal of NeuroEngineering and Rehabilitation
Functional electrical stimulation through direct 4-channel nerve stimulation to improve gait in multiple sclerosis: a feasibility study
Janet Hausmann 0
Catherine M. Sweeney-Reed 0 2
Uwe Sobieray 1
Mike Matzke 0
Hans-Jochen Heinze 0
Jürgen Voges 2
Lars Buentjen 2
0 Department of Neurology, Otto-von-Guericke University , Magdeburg, Leipziger Str. 44, 39120 Magdeburg , Germany
1 German Center for Neurodegenerative Diseases (DZNE) , Site Magdeburg, Leipziger Str. 44, Magdeburg , Germany
2 Department of Stereotactic Neurosurgery, Otto-von-Guericke University , Magdeburg, Leipziger Str. 44, 39120 Magdeburg , Germany
Background: Gait dysfunction due to lower limb central paralysis, frequently involving drop foot, is a common cause of disability in multiple sclerosis and has been treated with transcutaneous functional electrical stimulation (FES). We provide here the first report of 4-channel semi-implantable FES of the peroneal nerve which has been successfully used for rehabilitation in patients following stroke. Methods: FES was implemented via a 4-channel semi-implantable closed-loop system (ActiGait®, ©Ottobock), generating dorsiflexion in drop foot. Walking distance, gait symmetry (temporospatial gait analyses, Vicon Motion Systems®), gait velocity (10 m walking test) and quality of life (SF-36 questionnaire) were measured to evaluate the therapeutic benefit of this system in two patients with progressive MS. Results: Walking distance increased from 517 to 1884 m in Patient 1 and from 52 to 506 m in Patient 2. Gait velocity did not change significantly in Patient 1 and increased from 0.6 to 0.8 m/s in Patient 2. Maximum deviations of center of mass from the midline to each side changed significantly after 3 months of stimulation compared to baseline, decreasing from 15 to 12 mm in Patient 1 and from 47 to 37 mm in Patient 2. Both patients experienced reduced pain and fatigue and benefits to quality of life. Adverse events did not occur during the observation period. Conclusion: We conclude that implantable 4-channel FES systems are not only feasible but present a promising new alternative for treating central drop foot in MS patients.
Functional electrical stimulation; Multiple sclerosis; Peroneal nerve; Central drop foot; Hemiparesis; Rehabilitation; Gait; Gait improvement; Neuroprosthetics; Quality of life
Multiple sclerosis (MS) is an autoimmune-mediated
disorder leading to progressive neurodegeneration, with
increasing disability in many patients despite modern
treatment approaches. Although recent surveys have
demonstrated the importance of walking for MS patients
], gait dysfunction occurs in 80 % of all MS patients
after a 10 to 15 year disease duration [
], often due to
central paralysis of the lower limbs, and commonly
involving a drop foot. Gait disturbances can lead to
frequent falls [
] and a pathological compensatory gait [
Common treatment options such as walking aids, ankle
foot orthoses (AFO) to prevent forefoot floor contact
during the swing phase of walking, and pharmacological
treatments (such as the potassium channel blocker
fampridine and local or systemic antispastic therapy) show
only limited efficacy, with benefits only in individual
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Functional electrical stimulation (FES) was first
proposed in the 1960s as a stroke therapy [
]. It describes
application of an electric current to a nerve in order to
induce muscle contraction and thereby assist in
performance of a functional activity such as walking. The
ActiGait® System (details of the operation mode are
described below) was officially approved in Germany in
2007 for hemiplegia following ischaemic or hemorrhagic
stroke. Because the ActiGait System has been recently
introduced, many studies investigating its use have not
yet reached publication. We therefore enquired directly
with Ottobock, who reported that the device has been
implanted in approximately 400 post-stroke patients
(effective July 2015), but that implantation for other
indications remains rare.
Therapeutic success may be anticipated, however, in
upper motor neuron damage regardless of etiology [
Moreover, benefits have been reported in MS patients
either receiving surface FES [
] or by use of a
2channel implanted system that stimulates the two
branches of the common peroneal nerve [
Difficulties reported by some of our patients in handling a
surface FES system, and sensory side-effects resulting from
external attachment of the electrodes, led us to
investigate whether the advantages offered by an implantable
system could include reduced sensory side-effects. We
provide here the first report of successful
implementation of FES applied directly to the peroneal nerve via an
implanted 4-channel cuff electrode to aid dorsiflexion in
MS in two patients. Both patients, suffering from
progressive disease and central drop foot, experienced
considerable improvement in gait physiology, with
significantly increased walking distance, as well as
significant enhancement of quality of life (QoL).
An electrode cuff for FES of the peroneal nerve
(ActiGait®, ©Ottobock) was implanted in two patients
suffering from foot drop secondary to MS. Approval by the
local ethical review committee and informed consent
regarding off-label use of the device was obtained
Patient 1 was a 53-year-old lady who was diagnosed
with MS in 2002 after developing right-sided
hemihypesthesia, and followed a relapsing-remitting
course. In retrospect, a transient sensory disturbance
caudal from dermatome T10 in 1992 was in fact the
first episode. A further episode, involving numbness
of the right foot, followed in 2002. A slowly
advancing, persistent mild paresis of the left leg affecting
dorsiflexion and eversion of the foot began in
December 2005. Ankle-twisting with increasing walking
distance limited her walking distance to 500 m. The
patient also suffered from temporary episodes of general
fatigue. The disease evolved into a progressive course
without further symptom remission. The Expanded
Disability Status Scale (EDSS) [
] score was 3.5/10. The
diagnosis of MS was supported by cerebral MRI lesions
and delayed somatosensory evoked potentials (SSEP).
Immunomodulatory treatment with Interferon
beta1a (Avonex, Biogen Idec) was administered from
2003–2013, then discontinued following 8 years
without exacerbations and increasing needle phobia.
Symptomatic treatment of gait disturbance with
Fampridine retard 2x 10 mg (Fampyra, Biogen Idec) from
2011 led to a more fluent gait pattern and facilitated
stair climbing. Despite weekly physiotherapy, the drop
foot remained impairing and walking distance did not
improve. Because the movement limitations were only
debilitating over longer distances, an AFO or other
walking aid were not deemed to offer benefits
outweighing their inconvenience.
At referral in April 2013, walking required
considerable concentration, with frequent stumbling due to
forefoot catching and ankle twisting, especially with
increasing walking distance. After walking 500 m, the
patient suffered from left leg pain. Neurological
examination of motor skills revealed a mild distal left
hemiparesis, particularly of the lower limb, with mild spasticity.
The passive dorsiflexion/plantar flexion range exceeded
30° with a leg-foot-angle of approximately 90° in
maximum passive dorsiflexion in a stretched leg position.
Muscle strength in the left leg, rated according to the
British Medical Research Council (BMRC) criteria, was
as follows: hip flexion 4/5, knee flexion 4/5, other
proximal movements 5/5, ankle dorsiflexion 1/5, pronation
2/5, supination 4/5, plantar flexion 5/5. Sensory system
examination revealed hypesthesia of the left lower leg
and foot, with pallhypesthesia of 5/8 over the left and 8/
8 over the right malleolus, measured using a Rydel
Seiffer tuning fork, Position-, temperature- and pain
sensation were intact. Her gait pattern was spastic-ataxic but
narrow-based. The outer edge of the foot dropped
during the swing phase, with the forefoot dragging over the
floor with increasing walking distance. Mild spasticity of
the toes was present, with minimal ankle joint instability
and the gait was asymmetrical.
A four-week test phase with surface FES increased
walking distance and reduced effort on walking, but
sensory side-effects were not well-tolerated. We therefore
implanted an electrode cuff for FES of the left peroneal
nerve (ActiGait®, ©Ottobock) in September 2013. There
were no peri- or post-operative complications. After a
healing phase of 3 weeks, we activated the stimulation
Patient 2 was a 46-year-old man, diagnosed with MS
with a primary progressive course in 2007. He developed
a slowly deteriorating paresis of the right leg with a
disabling paresis of dorsiflexion (EDSS 6.5). With hindsight,
the first symptoms appeared in 1998, with right upper
limb weakness and numbness. Also of note is a spinal
disc herniation of lumbar disc 4/5 to the right side,
surgically treated in 2008.
On initial presentation in 03/2013, he reported a
walking distance-dependent physical fatigue with
increasing right leg weakness and forefoot catching,
with concomitant back, sacral, and pelvic pain.
Concentration was necessary to avoid stumbling, and he
required a cane and an AFO as walking aids. Fatigue
limited walking distance to 50 m using the AFO, and
he was unable to walk without the AFO due to ankle
twisting with each step.
Clinical examination revealed mild right hemiparesis
and moderate lower limb spasticity with contracture
of the calcaneal tendon. Passive dorsiflexion/plantar
flexion range exceeded 30°, with a leg-foot-angle of
approximately 90° on maximum passive dorsiflexion
in a stretched leg position. Muscle strength in the
right leg, according to BMRC criteria, was as follows:
hip flexion 3/5, extension 4+/5, abduction and
adduction 5/5, knee flexion 2/5, extension 5/5, ankle
dorsiflexion 1/5, pronation and supination 2/5, plantar
flexion 4+/5. Sensory examination revealed no sensory
deficits in the lower limbs. His gait pattern was
spastic-ataxic with circumduction of the right leg,
initial forefoot-floor-contact, and dropping of the
forefoot and outer edge during the swing phase. After a
few steps, he began to drag his right leg, followed by
the onset of spasticity of the toes and instability in
the ankle and knee joints. As for Patient 1, MRI and
electrophysiological findings supported the diagnosis
Immunomodulatory therapy was conducted with
Interferon beta-1b 0.25 mg/ml (Betaferon, Bayer Health
Care) every other day from diagnosis. He received no
antispastic treatment. A temporary treatment with
Fampridine retard 2x 10 mg (Fampyra, Biogen Idec) did not
improve walking with the cane and AFO.
Although we observed a clinical benefit following a
4week test phase with surface FES, the patient
experienced difficulties with exact electrode positioning, and
moreover, the electrodes were easily dislodged during
walking. Surface FES was therefore deemed unsuitable
for daily use, resulting in the decision to employ an
implanted FES system for direct stimulation of the right
peroneal nerve. We implanted the ActiGait® system in
November 2013 without complications and activated it
5 weeks later.
ActiGait® (©Ottobock) is a semi-implantable closed-loop
FES system generating dorsiflexion in drop foot (see
Fig. 1). The system is adapted to individual gait phase
and velocity by registering the patient’s heel lift through
an externally placed heel switch. The control unit worn
around the patient’s waist receives this trigger signal
wirelessly and generates a variable electromagnetic field
in the coiled antenna, which is connected to it.
Transcutaneous electromagnetic induction is used to transfer
the power and control signals to the implanted
stimulator, which generates the stimulation pulses in 4
independent current sources. These impulses are then
delivered through a dual lumen cable to 4 circularly
arranged sets of electrodes embedded within a 23 mm
silicone cuff. Each of the 4 channels can be controlled
independently of the other channels, thus enabling the
programmer to control the volume of tissue activated
within the nerve. The fascicles of the common peroneal
nerve can thus be selectively stimulated to trigger a
balanced dorsiflexion of the foot while avoiding stimulation
of sensory fascicles.
Evaluation of gait symmetry, comprising walking
distance measurement and gait velocity, as well as quality
of life (QoL), using the SF-36 questionnaire [
Fig. 1 Components of the ActiGait stimulation system. The control
unit worn around the patient’s waist receives a trigger signal
wirelessly from the externally placed heel switch when heel lift is
registered. It generates a variable electromagnetic field in the coiled
antenna, which is connected to it. Transcutaneous electromagnetic
induction is used to transfer the power and control signals to the
implanted stimulator, which generates the stimulation pulses in 4
independent current sources. These impulses are then delivered
through a dual lumen cable to 4 circularly arranged sets of
electrodes within a 23 mm silicon cuff electrode, and selectively
stimulate the fascicles of the common peroneal nerve and thus
trigger balanced dorsiflexion of the foot
performed before implantation of the electrode, after the
stimulation was first commenced (referred to as
“activation day”), and again 3 months later.
We used the 3D-Kinematicsystem from “Vicon
Motion Systems, Oxford UK” to capture the kinematics,
required for gait velocity measurement and for calculation
of the patient’s center of mass to quantify gait symmetry.
Markers were placed on the head, trunk, and limbs in
accordance with the Plug-In Gait software package,
which corresponds with the clinical gold standard in gait
analysis. To avoid inclusion of acceleration and braking
phases in the gait velocity measurements, the walking
space provided for patients had a total length of 8
meters, suitable for recording a walking distance of at least
4 meters. In order to maintain balance with an
asymmetric gait, trunk, limb and head movements may be
employed, stabilizing the gait by shifting the center of
]. The change in gait resulting from stimulation
can be quantified by calculating the shift in the patient’s
center of mass after stimulation. The motion capture
system allows the patient’s center of mass to be
calculated, based on the position locations of the markers in
3-D space, thus providing a holistic view of the body as
a single moving system in equilibrium in the transverse
] and thereby a measurement of the effect of
the stimulation on gait. Total walking distance in meters
was measured in the clinic corridor. The patients were
asked to walk until they no longer felt able to continue.
Gait velocity was defined as speed over a distance of 10
meters, measured three times with and without
stimulation. Both examinations took place on different days to
avoid bias of results by fatigue. Gait velocity and gait
analysis were performed successively with a pause of at
least 30 min for recovery.
T-tests were applied to provide a quantitative indicator
of the significance of the changes in the assessment
measures following stimulation treatment. The two
measurements of walking distance on activation day, first
without, then during stimulation, were compared with
the two measurements performed 3 months later. The
three measurements of gait velocity performed on
activation day before stimulation was commenced were
compared with three measurements made 3 months
later during stimulation. The difference between these
values reflects both the efficacy of the device and the
improvement made over the time of its use. Simulation
supports the validity of T-tests with low sample
numbers, defined as N = 2 to 5. [
]. The QoL questionnaire,
completed before stimulation commencement and
repeated following 3 months of stimulation treatment,
consists of 36 items, each rated on a scale from 0 to 100.
In order to provide an indication of whether QoL was
generally improved following treatment, each of the 36
items was taken as a separate indicator, providing 35° of
We measured the maximum deviations of center of
mass to each side from the midline for each gait cycle
pre-operatively and 3 months post-operatively. For
Patient 1, two gait cycles were completed at each
assessment (N = 4, including both sides), and Patient 2
completed 3 gait cycles (N = 6, including each side). The
absolute difference between the two sets of distance
measures was subjected to a T-test of the null hypothesis
that the deviations from the midline post-operatively did
not differ from those measured pre-operatively.
In Patient 1, with stimulation switched on, balanced
dorsiflexion was obtained in the ankle joint without
sensory side-effects. Dorsiflexion was adequate to prevent
contact between the outer edge of the foot and the floor
during the swing phase. A plain stabilization of ankle
and knee joint during the stance phase was already
apparent on first activation of the system. Hyperflexion
tending to genu recurvatum no longer occurred. After
3 months, the patient reported an improvement in
walking and an increased sense of security. With increasing
walking distance (more than 500 m), the benefits of
stimulation on walking became more evident. She
demonstrated a nearly symmetrical gait pattern under
stimulation. The drift to each side on gait analysis measured
post-operatively during stimulation differed significantly
from pre-operative measurements (one-sided paired
Ttest: T = 5.24, p = 0.014) with an average decrease from
15 to 12 mm (Fig. 2). Moreover, it may be observed that
the centre of mass was more central post-operatively.
Without stimulation, her gait pattern remained nearly
unchanged compared with preoperatively, though the
ataxic component was less distinct.
Walking distance increased more than threefold from
517 m to 1884 m after 3 months of stimulation (orthotic
effect of FES). Moreover, the patient could walk 1075 m
when stimulation was turned off, suggesting a
therapeutic effect of FES in addition (Fig. 3). Postoperatively,
walking distance was significantly increased with the
stimulation activated compared with off (one-sided
paired T-test: T = 14.3, p = 0.022). There was no
significant change in maximum gait velocity over 10 m
(onesided paired T-test: T = 1.6, p = 0.13; Table 1).
Evaluation of QoL parameters using an SF-36
questionnaire revealed various improvements compared with
preoperative statements (one-sided paired T-test:
T = −3.2, p = 0.0015), especially pertaining to parameters
of physical as well as emotional health; in particular pain
and fatigue were reduced. The patient reported a marked
change in general health (Fig. 4). Patient 1 has received
an invalidity pension since having bronchial carcinoma
in 1992, so effect on occupation was not assessed.
In patient 2, ankle stability improved markedly, and
walking was facilitated, including an ability to cover
longer distances. After 3 months, walking-dependent
pain had subsided. The patient was able to resume
his profession in food control, working in field service
3 days a week. Maximum walking distance improved
from 52 m preoperatively with an AFO to 506 m
after 3 months of using FES (Fig. 3). Postoperatively,
walking distance was significantly increased with the
stimulation activated compared with off (one-sided
paired T-test: T = 7.85, p = 0.040) and with an AFO in
the absence of stimulation (one-sided paired T-test:
T = 6.86, p = 0.046). A walking distance of 176 m
remained after turning the system off. The EDSS
score was improved by 0.5 points. Remarkably, the
patient was able to walk a distance of 46 m without
an AFO or FES 3 months after activation (Fig. 3).
Maximum gait velocity had increased from 0.6 to
0.8 m/s immediately after activation, persisting after
3 months of FES, and velocity during the on versus
off mode differed significantly (one-sided paired
T-test: T = − 8.9, p = 0.006; Table 1). The drift of
center of mass from the midline 3 months after
commencement of treatment showed a trend to a
reduction in patient 2 (47 vs. 37 mm; one-sided paired
Ttest: T = 2.44, p = 0.059).
SF-36 questionnaire evaluation demonstrated
improvements in physical and emotional health (one-sided
paired T-test: T = −1.7, p = 0.048). The patient reported
reduced pain and fatigue, and experienced fewer
physical, health-related role limitations on resuming work
Table 1 Gait velocity under different stimulation conditions.
Table 1 shows gait velocities in patient 1 and patient 2 on
activation day and after 3 months. In patient 1 there was no
significant change in maximum gait velocity over 10 m
(onesided paired T-test: T = 1.6, p = 0.13). In patient 2, however,
maximum gait velocity had increased significantly immediately
after activation, persisting after 3 months of FES, and on and off
mode also differed significantly at each time point (one-sided
paired T-test: T = − 8.9, p = 0.006)
After 3 months
Dropping of the forefoot in the swing phase of gait can
cause stumbling and falling [
]. A central drop foot is
often accompanied by ankle instability simply during
standing, as well as in the stance phase of the gait,
increasing the risk of the ankle twisting, as commonly
observed clinically. Moreover, walking becomes effortful
and slow, potentially shortening walking distance [
]. Degenerative joint or back pain due to
compensatory weight shift may develop in the long term, as
observed in Patient 1.
Patients with drop foot often depend on walking aids
such as an AFO, which acts passively as a cast. The main
disadvantage in using an AFO is that it does not cause
muscle contraction and can thus lead to further joint
immobilization. It also lacks the sensory feedback of
muscle contraction compared with FES. Moreover,
spasticity of the toe flexors, as experienced by Patient 2, can
cause pressure sores. FES via surface or implantable
electrodes offers a means of compensating for these
issues. The few studies reported evaluating implantable
FES systems found improvements in gait parameters and
QoL in post-stroke patients [
]. The ActiGait®
system has been employed in a number of studies to date,
and few adverse events have occurred [
the motor response is similar using surface compared
with implanted FES , the potential risks of surgery
may be outweighed by several advantages offered by
implanted over surface FES. Firstly, the electrode cuff, with
its 4 channels placed circularly around the target nerve,
generates the required motor response more precisely
than surface stimulation. Because 4 potential channels
are available for treatment, an optimum balance between
dorsiflexion and eversion for the individual patient can
be achieved. In some cases, for instance, a better
orthotic effect, with greater ankle joint stability, can be
obtained by distinct eversion. Secondly, the patient is not
required to apply the electrode to the leg, which takes
time, and moreover can be difficult to perform correctly,
as reported by patient 2. The use of an implantable
system could thus potentially lead to more consistent use
of the device, with a concomitant increase in the
therapeutic effect. Thirdly, discomfort due to electrical
stimulation is minimal, because applying the current directly
to the nerve avoids stimulation of non-target nerves,
eliminating sensory side-effects, which cannot be
achieved using a skin- mounted electrode. FES with an
implantable multichannel system can therefore be more
comfortable, as experienced by patient 1.
We provide here the first report of an implantable
4channel FES system in patients with MS. A 2-channel
system was implanted in 46 patients with central drop
foot of mixed etiology, including 17 MS patients, and
provided promising results, which have thus far been
presented as preliminary findings [
]; gait performance
improvement was similar to that provided in the same
patients using a surface stimulation system. The method
of fixation, however, whereby the electrode is sewn
directly onto the nerve, resulted in considerable adverse
effects, with temporary nerve dysfunction in 10 cases,
implant failure in 6 cases, and one infection resulting in
4 explantations [
]. The authors report improved
results with reduced sutures [
], and preliminary
longterm findings were reported in a recent conference,
whose proceedings are not yet available [
benefits in terms of gait parameters, QoL, and fatigue
reduction found in the few studies investigating surface FES in
MS patients were similar to those reported in stroke
]. Moreover, the approach compared
favorably with the current gold standard of AFO, both in
terms of subjective patient reporting and measureable
outcomes of improved walking distance and gait
symmetry. These findings are consistent with randomized
controlled trials comparing AFO with implanted FES
post-stroke that demonstrated comparable improvement
in gait and QoL [
] as well as superiority of FES for
obstacle avoidance [
Our patients demonstrate that implantable FES can
lead to considerable improvements in gait parameters
and QoL. Over the short 3-month observation period,
the patients showed an orthotic effect as well as a
rehabilitation benefit on walking distance, and increased
walking distance impacted QoL considerably. The
second patient was able to walk over 500 m with the
stimulation system switched on, compared with 50 m before
implantation, enabling the patient to walk outside the
home and to resume employment. Both patients
reported decreased pain, which may result from reduced
abnormal joint loading due to pathological
compensatory gait patterns and effort in ambulation. In patient 1,
although the more balanced and centered gait pattern
was observable clinically, the improvement in gait
symmetry measurement was less marked than in patient 2.
With temporospatial gait analysis, we sought to quantify
our clinical observations using a readily measurable
component of gait symmetry and found a small but
nonetheless statistically significant reduction in drift of
center of mass to each side. In patient 1, the increase in
walking distance was the more pronounced
improvement. In patient 2, the more marked reduction in drift is
likely to be because this patient showed a more
pronounced asymmetry of gait before the intervention. The
difference in findings between these two patients, both
of whom reported gait improvement following
stimulation treatment, underlines the importance of using a
range of outcome measures in quantitative outcome
Both patients experienced reduced fatigue despite
being more active. Social factors also improved, possibly
due to increased self-sufficiency and participation,
resulting from increased mobility. The current standard
therapy for drop foot is an AFO. Our second patient
reported an improved walking experience over longer
distances with FES in comparison with the AFO, resulting
in increased walking distance and gait symmetry. Recent
randomized controlled trials comparing AFO with FES,
including both surface as well as implanted FES in
poststroke patients, showed FES to provide equivalent
improvement in gait and QoL to AFO [
] and enhanced
obstacle avoidance ability [
]. In another study, stroke
patients evaluated surface FES in a structured interview
as generally superior to different kinds of AFO [
MS patients only reported advantages from FES in terms
of increased walking distance, fitness and physical
]. These findings are consistent with the
statements from our second patient, who used an AFO
before receiving FES.
After 3 months using the FES, the second patient was
able to walk a distance without technical assistance that
he could only achieve with the use of an AFO
preoperatively. This improvement is consistent with
findings using surface FES, which show that stimulation may
lead to enhancement of motor cortex neuroplasticity
]. It is moreover likely that the regular muscle
contraction brought about during the use of the FES led to
improvements in muscle strength, which do not occur
when the ankle is held in a fixed position with an AFO.
The progressive character of MS may be considered as
a critical difference between post-stroke and MS
patients. However, patients who have suffered a stroke are
recognized to be at risk of further cerebrovascular events
due to the persistence of the underlying pathology, such
as arteriosclerosis or atrial fibrillation. Even if a further
episode leads to persisting or additional deficits, the
patient may still benefit from assisted dorsiflexion of the
foot. If motor function of the ipsilateral leg diminishes,
ActiGait® allows adaptation of stimulation parameters,
for example to increase the amplitude of dorsiflexion.
Many MS patients also remain stable for long time
periods due to new and effective immunomodulatory basis
], and may therefore also be suitable
candidates to receive an implantable FES system. The
disadvantages of surface over implantable FES, such as poor
tolerance of sensory effects, and difficulties with
electrode placement, thus support the use of implantable
rather than surface FES, even in progressive disorders.
We conclude that implantable FES systems are a feasible
new option for treating central foot drop in MS patients.
We demonstrate improvements in gait parameters, and
reduction of pain and fatigue, as well as positive changes
in quality of life in two individuals suffering from
progressive MS treated with an implantable device for FES
of the peroneal nerve. The 4 channel cuff FES system
appears to offer the recognized advantages of an
implantable system compared with surface stimulation and
moreover offers the possibility of achieving these
benefits with fewer side-effects and complications than those
encountered using a system in which the electrodes are
sewn directly onto the nerve. The success of the therapy
in this preliminary study paves the way for a larger trial
to evaluate the benefits and general safety of the
AFO: Ankle foot orthosis; EDSS: Expanded disability status scale;
FES: Functional electrical stimulation; MRI: Magnetic resonance imaging;
MS: Multiple sclerosis; Pt.: Patient; QoL: Quality of life; SSEP: Somatosensory
The authors declare that they have no competing interests.
LB conceived the study, participated in study design and coordination,
conducted patient screening and selection, selected the implant, conducted
surgery, analyzed and interpreted the gait and quality of life data, drafted
and critically revised the manuscript. JH participated in study design and
coordination, conducted patient screening, selection and medical care,
participated in data acquisition, analyzed and interpreted the gait and
quality of life data, drafted and critically revised the manuscript. CMSR
assisted in data analysis and interpretation and drafted and critically revised
the manuscript. US acquired the data for gait analysis and helped in analysis
and interpretation of it. MM provided medical care and critically revised the
manuscript. HJH and JV contributed to conception and design of the study.
All authors read and approved the final manuscript.
We would like to offer our special thanks to Heike Stephanik for referring the
first patient to us. We also thank Prof. Emrah Düzel for offering equipment
and staff for accomplishment of gait analysis.
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