Functional electrical stimulation through direct 4-channel nerve stimulation to improve gait in multiple sclerosis: a feasibility study

Abstract

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.

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

Fig. 2

Undulation of center of mass along the line of progression. To evaluate gait symmetry, we examined the undulation of center of mass along the progression line with a temporospatial gait analysis. Preoperatively, the center of mass was located on the non-paretic side of the body, and the position of the center of mass moved to the left and right sides with a great amplitude, with varying degrees of severity, in both patients. In both patients gait symmetry increased after 3 months under stimulation, with less drift to both sides and a shift of the center of mass to the center of the body while walking

Fig. 3

Walking distance in longitudinal follow up. Walking distance under different conditions preoperatively, at activation day and after 3 months. Stimulation therapy led to increased walking distance in both patients. In patient 1 walking distance increased 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. Postoperatively, walking distance was significantly increased in patient 1 with the stimulation activated compared with off (one-sided paired T-test: T = 14.3, p = 0.022). In patient 2 maximum walking distance improved from 52 m preoperative with an AFO to 506 m after 3 months of using FES and to 176 m with AFO. 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 AFO in the absence of stimulation (one-sided paired T-test: T = 6.86, p = 0.046). Remarkably, the patient was able to walk a distance of 46 m without an AFO or FES 3 months after activation

Fig. 4

Quality of life using SF-36 questionnaire. Different parameters of quality of life are presented with a radar chart. We see different patterns of changes in both patients, but consistent improvements in both in physical, emotional and general health, absence of pain and benefits in energy and fatigue. Bar charts show total scores of the SF-36 questionnaire with significant improvements compared to preoperative statements in both patients (one-sided paired T-test; pt. 1: T = −3.2, p = 0.0015; pt. 2: T = −1.7, p = 0.048)