Effect of vibration in the treatment of children with spastic diplegic cerebral palsy

1. Introduction

Cerebral palsy (CP) is one of the leading causes of movement and posture disorders, which occurs with 2-3 of every 1000 individuals [1]. The majority of people with CP have the spastic syndrome of which the diplegic group is the smallest [2].

Spastic diplegic cerebral palsy usually affects muscle control and coordination, and affected people have increased muscle tone which leads to tight muscles and exaggerated reflexes. Leg muscles tend to be extremely tight [3]. So, the main treatment goal is to reduce stiffness in joints and increase the range of motion.

Various methods such as Vojta, Hippotherapy, Hydrotherapy, Massage, Casting and others are applied to children with cerebral palsy to manage spasticity and contractures, to improve muscle strength, motor activities, functions and self-care [3]. Recently a rising interest in the use of vibration for achieving therapeutic or physical performance goals has been observed [4-8].

Most authors hypothesize that vibrations stimulate muscle spindles and alpha-motoneurons, which initiate a muscle contraction. An immediate effect of a non-exhausting vibration session is an increase in muscle power. Scientific findings suggest that vibration could represent an effective exercise intervention for enhancing neuromuscular performance [9]. The frequency of vibration devices typically ranges from a few Hz to 50 Hz, with amplitudes ranging from a few micrometers to several millimetres, and entire session takes from 5 to 20 minutes [5]. The findings of researchers suggest that whole body vibration may improve mobility in children with cerebral palsy through a positive effect on the leg muscles [8]. Some authors found out that whole body vibration is safe and can be used in children with CP, as it is usually well tolerated by children with cerebral palsy and may improve standing function [5, 7, 10]. The research in adults with CP suggests that whole body vibration has no negative effect on spasticity [11].

Therefore, the aim in this clinical intervention was to compare the effect of conventional therapy and vibration in addition to conventional therapy in patients with spastic diplegic cerebral palsy in terms of spasticity, range of motion and standing, as well as mobility functions of Gross Motor Function Measure.

2. Methods

3. Intervention

All subjects participated in a 3-week (14 procedures, 45 minute sessions every working day) physiotherapy program. The conventional physiotherapy program consisted of stretching (Achilles tendon, hamstrings, hip flexors and extensors, abdominals), muscle strengthening (spine extensors, lower abdominals, hip and knee extensors, ankle dorsiflexes) and balance training exercises with Swiss balls, balance pads, and sticks. Each exercise was repeated 7-10 times within 2-3 sessions.

In addition to the conventional physiotherapy program, participants in Vibration group received vibration on a commercially available device (Swing Massager – HM01-08YA, China) with a side-alternating vibration along the sagittal axis (Fig. 1).

Fig. 1Position of the legs during vibration

In this study, the device was set to produce a peak to peak-sinusoidal vibration with the amplitude ranging from 2 to 6 mm. There were three positions illustrated on the device marked as ‘1’, ‘2’, and ‘3’ corresponding to peak-to-peak displacements of 2 mm, 4 mm, and 6 mm and four sets of duration: 5, 10, 15 and 20 min. During vibration, the patient had to lie on a couch with their legs put on the massager. The frequency used in this study was 15 Hz. At the beginning of intervention vibration duration was 5 min (plus 40 min of exercise), after 7 procedures ‒ 10 min. (and 35 min. of exercise). Before applying vibration, vibration tolerance test was done. The protocol of both interventions is presented in Table 1.

The study was approved by the Institutional Ethics Committee. Informed consent was obtained from parents or the legal guardians of all children.

4. Outcome measures

Range of motion (ROM) [12]. ROM of hip flexion and extension, ankle dorsal and plantar flexion were measured. The purpose of these measurements was to assess spasticity-related changes in ROM.

Spasticity of knee extensors was evaluated applying the Modified Ashwort scale (MAS) [13]. This scale grades the level of resistance to passive movement. The MAS has 6 degrees (0, 1, 2, 3, 4, and 5).

Gross motor functions were measured with GMFM-88 [14]. It consists of 88 items within 5 dimensions: (A) lying and rolling; (B) sitting; (C) crawling and kneeling; (D) standing; (E) walking, running and jumping. The items are scored using a 4-point scale (0 – does not initiate task; 1 – initiates task (< 10 %); 2 – partially completes task (10-99 %); 3 – completes task (100 %) and the scores are presented in percentages. Dimensions D and E were assessed in this study.

All measures were performed at a baseline and after the 3-week intervention.

5. Statistical analysis

The statistical analyses were performed using statistical package for social sciences (SPSS) version 20. Descriptive statistics (mean and standard deviation) were computed for all data. Wilcoxon’s signed rank test was used to analyse differences before and after intervention, and Mann-Whitney $U$ test – to analyse differences between the two groups. The difference across the groups and trials were considered statistically significant when $P$ value was less than 0.05. As all subjects completed interventions, no adjustments were needed for drop-outs. No power analysis was undertaken for the present study.

6. Discussion

The aim of this study was to compare changes in ROM, spasticity and motor functions after 3-week intervention applying conventional physiotherapy and vibration in addition to conventional physiotherapy. There has been limited research on the effect of vibration in the treatment of children with spastic diplegic cerebral palsy, although numerous studies have confirmed the beneficial effects of whole body vibration exercise on the musculoskeletal system [4, 15, 16], and mobility [7, 8].

In the present study, the results reveal significant improvement in ROM, spasticity and gross motor functions after both interventions. Spasticity is considered to be a primary limiting impairment in children with spastic diplegic CP and the goal in any treatment programme is to improve both passive and active movements. Significant reduction of spasticity in legs let children from both groups to perform leg movements in higher amplitude ($p$ < 0.05). Hence, increase in ROM and reduction of spasticity improved standing and mobility functions in all children significantly, but there were no significant differences between groups after two different interventions ($p$ > 0.05).

Ibrahim et al. conducted a study in which subjects – children with spastic diplegic cerebral palsy were divided into two groups: the whole body vibration group received conventional physiotherapy and vibration, and the control group received only the conventional physiotherapy. After 12 weeks of interventions spasticity decreased and motor functions improved in both groups, but significant difference between groups was found in 6 min. walk test and GMFM E dimension (walking, running, jumping – mobility) with better results ($p$ < 0.05) in WHV group [15].

Ruck et al. have demonstrated that vibration therapy is safe and has some effect on mobility in children with cerebral palsy, but there still is a need of standardized methods [7]. Researchers [6-8, 15, 17, 18] examine effect of WBV with different frequencies for balance and gait training, for speed, balance, and proprioception, ROM and functional activities (Table 5.).

In majority of studies analysing the effect of vibration, whole body vibration device was used when a patient had to stand in a vertical body position on a vibration plate. In our case we used a different device where a child had to lay down with their legs on the device. We found only one study analysing the effect of vibroacoustic therapy in the treatment of children with cerebral palsy where children were in a lying position during intervention. Katusic et al. found that intervention which lasted for 12 weeks was effective using vibroacoustic bed pad with treatment duration of 20 min. twice a week and frequency of 40 Hz [19].

This study has a number of limitations. The most important limitation is a short duration of intervention, as we investigated patients who came to rehabilitation only for three weeks from different regions of the country. The shortest vibration intervention mentioned in the scientific literature was 5 weeks [20]. Another limitation is a small number of participants. We assume that vibration interventions have a great potential in a therapeutic context, since they are well tolerated by children with spastic diplegia. Further studies with longer duration and follow-up assessment are needed to investigate the effect of vibration in the treatment programmes to improve clinical benefits.

7. Conclusion

The results of the present study showed that 3-week intervention of vibration in addition to conventional therapy and conventional therapy only, significantly increased range of motion, decreased spasticity in legs and improved standing and mobility functions in children with spastic diplegic cerebral palsy. There were no significant differences between the two groups after interventions in terms of spasticity, range of motion and standing, as well as mobility functions of Gross Motor Function Measure. A 3-week intervention, using vibration on a commercially available Swing Massager, is too short time to achieve clinical benefit.