Effects of Functional Electrical Stimulation on Gait in Cerebral Palsy

 

Milan Gregoric*; Hermina Damjan, Nusa Gros, Ana Klemen, Igor Tomsic

 

Institute for Rehabilitation, Republic of Slovenia, Ljubljana, Slovenia

 

 

Introduction

 

Several authors have reported functional and therapeutic benefits after the application of electrical stimulation to children with neurological disorders (1-3). A functional movement can be induced by electrical neuromuscular stimulation of the paralysed muscles with intact excitability of their peripheral innervation. A long-term use of electrical neuromuscular stimulation can strengthen the weak muscles, increases their endurance, improve the range of movement and reduce spasticity. The most widely used application of functional electrical stimulation (FES) is stimulation of the peroneal nerve and/or tibialis ant. muscle in adults and children with the foot drop due to chronic central nervous system lesions. However, the expected and desired beneficial effects of stimulation cannot be clearly predicted in individual patients with spastic hemiplegia or diplegia. There is still a lack of scientific data on short and long-term effects of electrical stimulation on abnormal movement patterns and abnormal muscle tone in children with cerebral palsy.

 

The aim of the present work is to provide some kinesiological data on the immediate orthotic and long-term therapeutic effects of  peroneal functional electrical stimulation (FES)  on the lower limb movements and on the forces engaged in the disturbed gait of hemiplegic and diplegic children with cerebral palsy. We also wished to investigate the effects of peroneal FES following the botulinum toxin therapy of the spastic plantar flexors of the foot. The working hypothesis is that the direct orthotic effect as well as long-term therapeutic effects of peroneal FES on gait in cerebral palsy may be enhanced if spasticity of the antagonists, i.e. plantar flexors of the foot is diminished by the botulinum toxin therapy. 

 

Patients

 

The immediate effects of FES were analysed in 30 ambulatory children with cerebral palsy: 20 with spastic hemiplegia, 10 with diplegia;  18 girls, 12 boys,  4 to 17 years old (mean age:  7.6 years).

 

The long-term effects of FES were analysed in smaller group of 5 children with hemiplegia and 2 children with diplegia.

 

The combined effects of FES and botulinum toxin treatment was studied in a group of 8 children with spastic hemiplegia: 7 girls and one  boy, 5 to 17 years old (mean age : 6.3 years).

 

Methods

 

Functional electrical stimulation (FES)

Two surface electrodes placed above the peroneal nerve. Stimulation was triggered by a switch in the sole of the shoe. Stimulation parameters: frequency 25 – 30 Hz, impulse width 0.4 – 0.6 ms. Intensity was individually adjusted.

 

Seven children (5 with hemiplegia and 2 with diplegia) were using FES for daily walking for a period of 5 to 6 months.

 

Botulinum toxin type A (Botox, Allergan) was injected in 8 hemiplegic children in spastic plantar flexors of the foot (gastrocnemius medial/lateral 3-6 Units/kg, soleus 2-3 Units/kg). Spontaneous and FES assisted gait were analysed before and 5 to 6 weeks after botulinum toxin application (1st control). FES was prescribed after the control investigations and the children were walking with FES (at least 2 to 3 hours daily) for 5 to 6 months after the botulinum toxin application and before the final gait analysis (2nd control).

 

Gait analysis

An optoelectronic system (Vicon 370; Oxford Metrics Ltd. – 5 cameras 50 Hz with infra-red strobes) was used for kinematic analysis. Two force-platforms (AMTI, model SGA6-4, Massachusetts, USA) built in the floor of the laboratory were used for kinetic studies. The children were walking freely, with their sport shoes on, with and without peroneal functional electrical stimulation (FES) applied in swing on the affected or more affected side.

 

Results and Discussion

 

Immediate effects of FES

 

Time and distance parameters

Calculated were no significant differences between the basic gait parameters measured on spontaneous gait and FES assisted gait (Table 1).

 

Table 1. Mean values and standard deviations (in parenthesis) of the basic gait parameters measured in free and FES assisted gait.

 

          

Cadence (step/min)

Velocity (m/s)

Stride length (m)

Double support (%)

Hemiplegia (N=20)

 

 

 

 

Without

109.6 (21.3)

0.81 (0.2)

0.87 (0.2)

30.4 (5.2)

FES

107.9 (15.9)

0.80 (0.2)

0.88 (0.1)

29.5 (4.3)

Diplegia (N=10)

 

 

 

 

Without

94.4 (17.6)

0.62 (0.3)

0.71 (0.2

36.0 (6.9)

FES

100.2 (17.0)

0.66 (0.2)

0.75 (0.2)

35.8 (7.8)

                                     

Kinematics

Increased dorsal flexion of the foot in swing associated with improved positioning of the foot in the terminal swing and initial contact was achieved by peroneal FES on the paretic side in 17 from 20 investigated children  with spastic hemiplegia and in 3  from 10 investigated children with diplegia. (Fig.1).  In 5 out of children with diplegia the excessive knee flexion in stance was decreased on FES assisted gait. 

 

Kinetics

 

FES induced changes in ankle torques and power closer to the normal  pattern in 8 from 20 children with hemiplegia and 4 from 10 children with diplegia (Fig. 1). The abnormal peak of the ankle torque and the negative power in the early stance phase were decreased when these children were walking with FES.

 

 

Long-term effects

 

A mild improvement of  time and distance gait parameters associated by improved dorsal flexion of the foot in swing  was detected on repeated investigations of free gait following 5 months of regular use of FES  in one (patient 5.) out of 5 investigated children with hemiplegia (Table 2.). Velocity and stride duration only were


Fig 1. Gait in a child with spastic hemiplegia (girl, 11 years)  walking freely without stimulation  and with peroneal FES (bold line).

 

increased in FES assisted gait on the control investigation in this child. The other 4 hemiplegic children who were using FES daily for 5 to 6 months showed no significant changes or even a mild decrease in the cadence, velocity and stride duration in free and FES assisted gait (Table 2.). A more pronounced improvement of the measured parameters was noticed in both investigated children with diplegia (patients 6.,7.). An improvement of the dorsal flexion of the foot in swing and improved initial contact, more normal torque and power curves were observed in 4 out of 5  investigated  hemiplegic children on repeated investigation following a period of regular use of FES. A tendency to a decrease in an excessive knee flexion in stance was observed in diplegic children as well.

 

Table 2.  The basic gait parameters measured during free and FES assisted gait in 5 children with hemiplegia and 2 children with diplegia before and after 5 to 6 months of  daily use of FES for walking.

 

 

Patients

Cadence

(step/min)

Velocity

(m/s)

Stride

length (m)

Double

support (%)

 

Hemiplegia

Before

After

Before

After

Before

After

Before

After

1

 Without

77.6

70.2

0.37

0.40

0.58

0.68

43.5

44.0

 

FES

85.8

69.0

0.48

0.35

0.68

0.61

38.5

38.5

2

Without

107.6

101.4

0.78

0.72

0.87

0.85

33.0

28.0

 

FES

108.0

91.8

0.78

0.63

0.87

0.82

31.0

29.5

3

Without

93.6

108.0

0.45

0.58

0.57

0.64

35.5

34.0

 

FES

96.0

106.2

0.48

0.53

0.60

0.60

32.5

36.0

4

Without

109.2

112.2

0.96

0.97

1.04

1.04

31.5

30.0

 

FES

101.4

99.0

0.85

0.85

0.64

1.01

33.0

33.5

5

Without

84.6

102.6

0.47

0.76

0.67

0.88

36.5

31.0

 

FES

90.0

87.6

0.52

0.65

0.69

0.89

32.0

31.5

 

 

 

 

 

 

 

 

 

 

 

Diplegia

 

 

 

 

 

 

 

 

6

Without

108.0

143.4

0.55

1.09

0.60

0.92

33.5

27.0

 

FES

92.4

147.6

0.45

1.15

0.59

0.93

35.0

28.0

7

Without

72.0

87.6

0.26

0.37

0.43

0.51

40.0

45.5

 

FES 73.2

73.2

84.0

0.30

0.37

0.49

0.53

52.5

40.5

 

Effects of FES after botulinum toxin treatment

 

In the investigations following botulinum toxin application to spastic plantar flexors of the foot the dorsal flexion of the foot in swing induced by FES was increased, while plantar flexion in the terminal stance and early swing was decreased in comparison to the investigations prior to the botulinum therapy in 6 out of 8 investigated hemiplegic children (Fig. 2). In these 6 children a mild but clearly visible decrease in the abnormal early peak of the torque and negative (absorptive) power on stance were associated by improved dorsal flexion of the foot in swing.

 

A less marked improvement of the dorsal flexion of the foot was observed after botulinum toxin application also during free walking (without FES) when compared to the records obtained prior to the treatment. The kinetic changes following the botulinum toxin application may be attributed to the clinically observed decrease of spasticity of the treated plantar flexors of the foot. On the other hand, the ankle torque and power were mostly decreased after botulinum toxin application, which is very probably due to the induced weakness of the treated muscles.

 

The described kinematic and kinetic effects were not associated by changes in the basic gait parameters measured during free and FES assisted gait. No significant changes in velocity, cadence, and duration of stride, step or double support period were observed on repeated investigations 5 to 6 weeks after botulinum toxin application to the spastic plantar flexors of the foot. After this second investigation the children started to use FES for walking at least 1 to 3 hours daily. In 5 out of 6 children who showed improved responses to FES already on the first examination a mild further improvement i.e. a decrease in the abnormal torque and power peaks and increased electrically induced dorsal flexion of the foot in swing were noticed in the last examination following the botulinum toxin treatment and a period of (5 to 6 months of) regular daily use of FES. These changes were not associated by the changes in the time and distance parameters of gait (Table 2.).

 

Conclusions

 

Peroneal FES results in an immediate increase in the deficient dorsal flexion of the foot in swing associated with improved initial contact in hemiplegic and diplegic children.

The kinematic and kinetic changes directly induced by FES are not clearly reflected in the time and distance parameters of gait.

 

FES may induce changes in ankle torques and power closer to the normal pattern.

A long-term  use of FES for walking might result in improvement of ankle movements in hemiplegic children mostly not associated by changes in the time and distance parameters of the gait.

 

An improvement of the ankle and knee movements may be associated by changes in the basic gait parameters following a long-term use of the peroneal FES in diplegic children.

Botulinum toxin therapy of spastic plantar flexors of the foot may enhance the direct effect of peroneal FES. The long-term additional effects of FES following botulinum toxin therapy in hemiplegic children are not clear. 

 

Further studies are needed to prove the beneficial effects of FES on the gait of hemiplegic and diplegic children.

 

Fig 2. Sagittal averaged goniograms of the right ankle in a 5 years old girl with spastic right sided hemiplegia walking with FES before botulinum toxin application to the plantar flexors of the foot (above) and after application (below).

 

Table 3. Mean values and standard deviations (in parenthesis) of the basic gait parameters measured in spontaneous and in FES assisted gait before botulinum toxin injection to spastic plantar flexors of the foot in 8 children with spastic hemiplegia, 5 to 6 weeks (1st control) later, and 5 to 6 months (2nd control) after the injection.

 

 

 

 

 

 

N=8

Cadence (step/min)

Velocity (m/s)

Stride length (m)

Double support (%)

BEFORE BTX

 

 

 

 

Without

116.7 (24.8)

0.89 (0.2)

1.03 (0.4)

29.0 (1.8)

FES

107.3 (19.8)

0.80 (0.2)

0.91 (2.3)

28.9 (2.3)