Static Posturography with Nintendo Balance Board in Children after Cochlear Implantation

Abstract

Human balance is essential for maintaining stable posture and safe mobility. Balance relies on the integration of various sensory and motor systems, including the audiovestibular, visual, and proprioceptive systems. Cochlear implantation can potentially affect the peripheral vestibular system, leading to balance disturbances. We studied postural balance in children after cochlear implantation (CI) using the Nintendo Wii Balance Board (WBB) with Wii Posturografie software. Balance was assessed in 77 children (14 with CI, 25 with sensorineural deafness, and 38 controls). Children under 8 years old after CI showed significant differences in postural balance compared to controls, while those over 8 years old did not differ significantly. The WBB with Wii Posturografie proves effective for evaluating postural balance in children. Understanding postural changes in CI recipients can aid in optimizing auditory rehabilitation and enhancing overall outcomes. Further long-term investigations are needed.

1. Introduction

Human balance is a multidimensional concept, referring to the ability of a person to avoid falling. It can be characterized as the potential of the body to maintain a stable posture for maximum time with minimal body sway. The integration and coordination of various body systems, including the audiovestibular, visual, and motor systems, as well as higher-level premotor systems, contribute to achieving balance. The central nervous system interprets information from sensory systems and produces a response to activate postural muscular synergies. These synergies are responsible for proper head, eye, and body movements to maintain posture [1].

Balance maintenance involves holding, attaining, or restoring the projection of a center of pressure (COP) relative to the support base, or generally within the limit of stability. The limit of stability is the maximum deviation of the body that a person can arbitrarily withstand in any direction without falling or having to take a step [2].

The functions of the balance system include [3]:

1. Maintaining a certain postural position, such as sitting or standing.

2. Promoting voluntary movements such as transitional movements between postures.

3. Reactions that restore equilibrium after sudden external stimuli such as a trip, a slip, or a push.

Balance control is essential not only to maintain postural stability but also to ensure safe mobility in everyday life, such as performing manual tasks while standing, lifting from a chair, walking, and turning.

The balance is usually tested on a force platform in a laboratory setting. Force platforms are commonly found in research laboratories, physiotherapy, and audiology departments because they can be used to identify most types of balance disorders, are available commercially, and have normative data associated with them [4].

During the study, the body sway data, a factor directly related to the balance, is obtained by recording the force vector applied by the body to the plane of the platform. The data obtained allow us to describe the body sway using several quantitative indicators accurately.

There are some important limitations. Testing on the force platform is a time-consuming procedure, the platform itself requires installation under the floor, which restricts its mobility and significantly increases the overall cost of the equipment. Thus, the classical force platform is difficult to use in conventional clinical practice.

The Wii Balance Board (WBB) device (Nintendo, Kyoto, Japan) is relatively inexpensive and available almost anywhere in the world, but it is potentially effective to perform an instrumental balance assessment in limited time and space clinical settings. This device resembles a typical force platform (Figure 1) and is a clinically useful tool for assessing balance [5].

Figure 1.

Wii balance board platform.

Scientists from several countries are using WBB with adapted or custom software, such as LabView (National Instruments, Austin, TX, USA), Balancia (Mintosys, Seoul, Korea), Wii Posturografie (Tomas Bata University, Zlin, Chech Republic) that communicates with WBB via Bluetooth to evaluate differences with laboratory-level force platforms [5, 6, 7]. WBB demonstrated excellent concurrent validity in comparison with force platforms to quantify static balance in healthy adults (ICC 0.77 to >0.99) and in patients with Parkinson’s disease (ICC = 0.92–0.98) after stroke (ICC = 0.82–0.98) [8, 9].

Various pathologies such as neurological disorders, sensory deficits, or muscle weakness can cause balance disorders.

Deafness is one of the most severe sensory deficits for an individual and for society as a whole. At the same time, vestibular dysfunction is often detected in children with congenital hearing defects. According to Jacot (2008), the vestibular function was symmetrically impaired on both sides in 18.6%, asymmetrically impaired in 32.6%, and was normal only in 37.2% of cases among patients with deafness [8].

Cochlear implantation (CI) is a state-of-the-art and the most effective method of deafness rehabilitation. More than one million patients worldwide are already users of cochlear implants [9].

Both intraoperatively and in the postoperative period of cochlear implantation, a negative effect on the peripheral part of the vestibular analyzer is possible due to several mechanisms:

• direct traumatization of the vestibule with an active electrode [10];

• intraoperative loss of perilymph [11];

• acute serous labyrinthitis after cochleostomy [12];

• the reaction of the labyrinth to a foreign body [13];

• endolymphatic hydrops [14];

• electrical stimulation of the labyrinth [15].

The following manifestations of vestibular dysfunction after exposure to the above factors have been described [11, 12, 16]:

• worsening of the existing vestibular dysfunction;

• the onset of vestibular dysfunction after CI;

• slowing down the development of motor skills;

• disequilibrium;

• dizziness caused by sound.

Given the critical social impact of CI, especially in children, all of these potential negative effects should be investigated in great detail. Despite a large number of clinical trials performed in the world and in Ukraine, the state of postural balance in patients in the long-term period has not been studied enough. This is due to the low motivation of the parents of implanted children to undergo additional examinations, especially in the absence of complaints in the child, as well as the unavailability of equipment for the study of balance in routine clinical practice.

Purpose of the study: To study the indicators of postural balance in children after cochlear implantation.

An observational cohort study included 38 children with normal hearing and no vestibular complaints, 25 children with sensorineural deafness (SND), and 14 children after unilateral cochlear implantation. The age of the children ranged from 2.8 to 17.9 years. The mean time after implantation was 3.2 years.

Static balance was assessed using the Nintendo Wii Balance Board (Nintendo, Kyoto, Japan) connected via Bluetooth to a Dell 3550 laptop (Dell Inc., Round Rock, USA). WBB accuracy in weight measurement was assessed by the state metrological enterprise “Ukrmetrteststandart”. Postural balance indicators were recorded using the Wii Posturografie software developed at the Department of Applied Informatics at Tomas Bata University (Zlín, Czech Republic) (Figure 2).

Figure 2.

Wii posturography software interface.

The study was conducted in a quiet medical office, the patient stood barefoot on the platform in a position with heels together, feet apart at an angle of 45°. The child was given up 30 s to adapt, then the balance indicators were recorded in a position with open eyes for 20 s. After that, the child was asked to close his eyes, after adaptation, the balance indicators were recorded in the position with eyes closed for the next 20 s [17]. All indicators in children after cochlear implantation were recorded with the processor turned on.

The following postural balance parameters were recorded: Way, Area, Lateral, Anterior-Posterior (AP), and AP/Lateral in the position with gaze fixation (Opened) and with eyes closed (Closed). The following indicators were calculated: Romberg Way, Romberg Area [18]. See Table 1a (Appendix) for the list of technical terms.

The following indicators are considered the most critical balance parameters:

The Way parameter (cm/s) describes the path of movement of the COP. Since the study time is set to a constant number, this parameter is characterized as the speed of COP.

$$\begin{array}{c}{M}_i=\sqrt{{\left(x_{i+1}-x_i\right)}_2+{\left(y_{i+1}-y_i\right)}^2}\\ W=\frac{T^{-1}}{n}\sum _{i=1}^n{M}_i\left[\mathit{mm}/s\right],\end{array}$$E1

Where:

1. Me – a separate element of the path calculation

2. T – study period

3. x,y – coordinates of COP

4. n – number of measurements

The Area parameter (cm²/s) marks the area and describes the variations in COP during the study.

$N_i=\frac{\left|\left(y_{i+1}-y_0\right)\ast \left(x_i-x_o\right)-\left(y_i-y_o\right)\ast \left(x_{i+1}-x_0\right)\right|}{2}$

$$A=\frac{1}{t}\sum _{i=1}^{n-1}{N}_i\left[{\mathrm{mm}}^2/\mathit{s}\right],$$E2

Where:

1. N_i – a separate element of the area calculation,

2. t – study duration [s],

3. x_O and y_O - average values of the coordinates of the center of gravity.

The AP parameter is the resulting anteroposterior center of gravity vector (the length of the anteroposterior COP shifts during the study).

$$\begin{array}{c}\mathit{sum}=\sum _{i=1}\left(y_i-y_{i-1}\right)\\ \mathit{Ant}‐\mathit{\text{Post}}=\mathit{sum}/t,\end{array}$$E3

Where:

1. t – study duration [ms],

2. y – the center of coordinates of COP.

The parameter Lateral (cm/s) is the resulting amplitude vector of the lateral displacements of the center of gravity (the length of the lateral displacements of the center of gravity during the study).

$$\begin{array}{l}\mathit{sum}=\sum _{i=1}\left(x_i-x_{i-1}\right)\\ \mathit{Lateral}=\mathit{sum}/t\end{array}$$E4

Where:

1. t – study duration [ms],

2. x – the center of coordinates of the center of gravity.

The AP/Lateral parameter is the ratio of the anterior–posterior and lateral balance components of the subject. It reflects the general dominance of the direction of the gravitational amplitude.

$$\frac{\mathit{AP}}{\mathit{Lateral}}=\frac{\mathit{Ant}-\mathit{\text{Post}}}{\mathit{Lateral}}$$E5

All parameters were recorded in two positions: with eyes open (opened) with gaze fixed on a still image and in a state with eyes closed (closed). In the first position, the vestibular system, visual posture control, and the proprioceptive system are involved in maintaining balance. In the second position, the participation of visual control in maintaining postural balance is excluded.

The Romberg Way parameter is the ratio of the Way values obtained in the study with the patient’s eyes open and closed.

$$\mathit{\text{Romberg}}\mathit{Way}=\frac{{\mathit{Way}}_{\mathit{\text{closed}}}}{{\mathit{Way}}_{\mathit{\text{opened}}}}$$E6

The Romberg Area parameter is the ratio of the Area values obtained in the study with the patient’s eyes open and closed.

$$\mathit{\text{Romberg Area}}=\frac{{\mathit{\text{Area}}}_{\mathit{\text{close}}}}{{\mathit{\text{Area}}}_{\mathit{\text{opened}}}}$$E7

The Romberg Way and Romberg Area parameters demonstrate the role of visual control in maintaining postural balance.

Statistical processing included testing the hypothesis that the sample distribution corresponds to a normal (Gaussian) distribution using the Kolmogorov–Smirnov and Shapiro–Wilk tests. The null hypothesis of the absence of differences between the samples in multiple comparisons was tested using the nonparametric Kruskal–Wallace test. The Spearman correlation coefficient was used to determine the relationship between individual indicators.

Differences between samples were considered statistically significant at a significance level p (probability of erroneously rejecting the null hypothesis) less than 0.05. Data analysis was carried out using the MedCalc statistical software (MedCalc Software Ltd., Ostend, Belgium). Graphs and figures showing the differences between the indicators were obtained using the MedCalc software.

2. Results and discussion

Based on the literature data [19, 20], we conducted a correlation analysis of the relationship between postural balance indicators and age in children with normal hearing (Figure 3). We recorded a trend toward a significant decrease in the values of indicators until the age of 8 years. With increasing age, the balance indicators stabilized or had a slight tendency to decrease. As a result of the subsequent analysis, we obtained significant differences in the values of the postural balance parameters Way, Area, and AP recorded in the position with eyes closed and the values of the AP parameter recorded with eyes open in children in groups younger than and older than 8 years (Table 1).

Figure 3.

Correlation analysis of postural balance parameters in children with normal hearing depending on their age. A. Parameter Area with opened eyes. B. Parameter Area with closed eyes. C. Parameter Way with opened eyes. D. Parameter Way with closed eyes.

	Under 8 years old; Median (95% CI)		Over 8 years old; Median (95% CI)
	Eyes opened	Eyes closed	Eyes opened	Eyes closed
Way, cm/s	1.38; (1.12–1.66)	2.05; (1.49–2.68)	1.15; (0.93–1.32)	1.56; (0.96–1.87)*
Area, cm/s^2	0.30; (0.15–0.34)	0.47; (0.27–0.64)	0.13; (0.10–0.29)*	0.23; (0.10–0.47)*
AP, cm/s	0.91; (0.78–1.17)	1.56; (1.09–1.87)	0.75; (0.64–0.92)	1.03; (0.71–1.22)*
Lateral, cm/sec	0.83; (0.66–1.02)	1.05; (0.8–1.52)	0.71; (0.54–0.78)	0.77; (0.55–1.25)
AP/Lateral	1.15; (0.95–1.29)	1.35; (1.16–1.54)	1.16; (1.03–1.23)	1.27; (0.98–1.54)

Table 1.

Postural balance parameters in normally hearing children.

Note: CI, confidence interval; *, the difference between indicators in groups under 8 and over 8 years old is statistically significant (p ˂ 0.05).

In this work, we divided all groups of children (control, CIS, after CT) into 2 age subgroups: up to eight and after eight full years.

The results obtained are shown in Tables 2–4.

Parameter	Median (95% CI)
	Eyes opened			Eyes closed
	Normal hearing	SND	Cochlear implantation	Normal hearing	SND	Cochlear implantation
Way, cm/s	1.38 (1.12–1.66)	2.50 (1.44–3.03)*	2.70 (1.98–4.65)*	2.05 (1.49–2.68)	2.59 (1.88–4.63)	3.78 (2.96–3.87)*
Area, cm/s^2	0.30 (0.15–0.34)	0.57 (0.30–1.44)*	0.88 (0.43–2.72)*	0.47 (0.27–0.64)	0.70 (0.46–1.65)*	1.45 (0.74–1.72)*
AP, cm/s	0.91 (0.78–1.17)	1.56 (0.99–2.12)*	2.04 (1.32–2.45)*	1.56 (1.09–1.87)	1.88 (1.37–3.19)*	2.71 (2.04–2.91)*
Lateral, cm/sec	0.83 (0.66–1.02)	1.56 (0.86–1.78)*	1.62 (0.90–3.39)*	1.05 (0.8–1.52)	1.43 (1.03–2.30)	1.99 (1.13–2.13)*
AP/Lateral	1.15 (0.95–1.29)	1.16 (1.04–1.25)	1.17 (0.79–1.48)	1.35 (1.16–1.54)	1.36 (1.16–1.57)	1.37 (1.36–1.80)

Table 2.

Postural balance parameters in children under 8 years old.

Note: CI, confidence interval; *, a significant difference was revealed between the parameter values in comparison with children with normal hearing (p ˂ 0.05).

Parameter	Median (95% CI)
	Eyes opened			Eyes closed
	Normal hearing	SND	Cochlear implantation	Normal hearing	SND	Cochlear implantation
Way, cm/s	1.15 (0.93–1.32)	1.03 (0.76–1.33)	0.89 (0.78–0.96)	1.56 (0.96–1.87)	1.59 (1.15–2.09)	1.45 (1.16–2.12)
Area, cm/s^2	0.14 (0.10–0.29)	0.17 (0.09–0.26)	0.14 (0.07–0.20)	0.23 (0.10–0.47)	0.27 (0.17–0.68)	0.25 (0.21–0.51)
AP, cm/s	0.75 (0.64–0.92)	0.73 (0.48–0.88)	0.62 (0.54–0.67)	1.03 (0.71–1.22)	1.21 (0.81–1.43)	0.96 (0.75–1.52)
Lateral, cm/sec	0.71 (0.54–0.78)	0.62 (0.46–0.82)	0.55 (0.44–0.57)	0.77 (0.55–1.25)	0.87 (0.70–1.19)	0.85 (0.65–1.00)
AP/Lateral	1.16 (1.03–1.23)	1.08 (1.05–1.36)	1.20 (1.10–1.33)	1.27 (0.98–1.54)	1.32 (1.20–1.61)	1.08 (1.01–2.14)

Table 3.

Postural balance parameters in children over 8 years old.

Note: CI, confidence interval.

	Under 8 years old; Median (95% CI)			Over 8 years old; Median (95% CI)
	Normal hearing	SND	Cochlear implantation	Normal hearing	SND	Cochlear implantation
Romberg Way	0.75 (0.55–0.82)	0.81 (0.76–0.95)	0.69 (0.59–1.65)	0.78 (0.58–0.97)	0.60 (0.46–0.81)	0.52 (0.45–0.76)
Romberg Area	0.59 (0.40–0.86)	0.69 (0.63–1.06)	0.72 (0.50–2.30)	0.74 (0.56–0.92)	0.53 (0.23–0.59)	0.34 (0.29–0.72)

Table 4.

Parameters Romberg way and Romberg area.

Note: CI, confidence interval.

2.1 Parameter way

In the position with open eyes (Opened) in children under 8 years of age, the Way parameter significantly differed from the control both in the group of children with SND and in the group of children after CI (p = 0.000260), and there was no significant difference between the SND and CI groups. At the same time, in children older than 8 years, there was no significant difference in the Way parameters between the groups.

In the position with eyes closed (Closed) in children under 8 years of age, the Way parameter was statistically significantly higher only in the CI group (p = 0.011218), in the control group and CIS there was no statistically significant difference.

In children older than 8 years, there was no statistically significant difference between the groups either in the position with eyes open (p = 0.225619) or in the position with eyes closed (p = 0.857089).

2.2 Parameter area

In the position with open eyes (Opened) in children under 8 years old, the Area parameter significantly differed from the control both in the SND group and in the CI group (p = 0.002558), there was no significant difference between the SND and CI groups. In the position with eyes closed (Closed), the Area parameter also significantly differed from the control both in SND and CI groups (p = 0.011060). There was no significant difference between SND and CI groups.

In children older than 8 years, there was no statistically significant difference in the values ​​of the Area parameter between groups either in the position with eyes open (p = 0.764298) or in the position with eyes closed (p = 0.736028).

2.3 Parameter AP

In children under 8 years of age in the open-eyed position, the AP parameter was significantly higher in the CI and SND group than in the control group (p = 0.000235). In the position with eyes closed, the indices in the CI and SND groups were significantly higher than in the control group (p = 0.005888). In children older than 8 years, there were no significant differences between the groups either in the position with open eyes (p = 0.233647) or with closed eyes (p = 0.555827).

2.4 Parameter lateral

In children under 8 years of age in the position with their eyes open, the values of the Lateral parameter were significantly higher in the CI and SND group than in the control group (p = 0.001432). In the position with eyes closed, the indices in the CI group were significantly higher than in the control group (p = 0.050336). In children older than 8 years, there were no significant differences between the groups either in the position with open eyes (p = 0.255820) or with closed eyes (p = 0.920133).

2.5 Parameter AP/Lateral

Both in children under 8 years of age and over 8 years of age, there was no statistically significant difference in the values of the AP/Lateral parameter between groups neither in the position with eyes open (p = 0.993532 for the age of up to 8 years, p = 0.733826 for age over 8 years) nor in the position with eyes closed (p = 0.622120 for age up to 8 years, p = 0.764711 for age over 8 years).

2.6 Romberg Way

We did not obtain a statistically significant difference in the values of the Romberg Way parameter in children of all ages in all study groups (p = 0.157695 for the age of up to 8 years, p = 0.191010 for the age of over 8 years).

2.7 Romberg Area

We also did not obtain a statistically significant difference in the values of the Romberg Area parameter in children of all ages in all study groups (p = 0.302631 for the age of up to 8 years, p = 0.195556 for the aged over 8 years).

3. Discussion

In otology practice all over the world, there is no single consensus on the need to assess vestibular function and balance before and after cochlear implantation, and on the scope of necessary examinations. Most cochlear implant centers do not routinely assess vestibular function in the pre- and postoperative period, some - only if there are relevant complaints (dizziness, balance disorders, impaired development of motor skills), in very few - all patients undergo preoperative and postoperative vestibular testing.

Most often, the lack of vestibular testing is due to technical difficulties in examining young children and good postoperative results - children and parents rarely complain of dizziness and balance disorders.

In the literature, there are a small number of publications devoted to the assessment of postural balance in children after cochlear implantation. The results obtained are ambiguous. For example, Nair et al. when performing static posturography in children aged 2–7 years, a significant decrease in vestibular indices was revealed in the examined children after CI [21]. Kelly et al. assessed postural balance using WBB and Vestio software in 10 children aged 9–18 years after CI, revealing a significant difference in the parameters in children after CI and non-implanted children with normal hearing [22]. No significant difference was found in the parameters of postural balance in the study by Buchman et al. [23]. Walter et al. [24] found a significant improvement of postural balance parameters in bilaterally implanted patients.

Our results complement the scientific knowledge about the state of postural balance in children after cochlear implantation. In our study, children under 8 years of age after CI demonstrated a significant difference in the values of postural balance parameters in comparison with children with normal hearing. At the same time, children over eight years of age demonstrate balance indicators that do not differ significantly from those of children in the control group.

4. Conclusions

1. The Wii Balance Board with Wii Posturigrafie Software is a convenient and effective tool for assessing postural balance in children with both normal hearing and children with sensorineural deafness and after cochlear implantation.

2. In children under 8 years of age after cochlear implantation, a statistically significant increase in the values of the parameters Way, Area, AP, and Lateral in the position with open and closed eyes was revealed in comparison with children with normal hearing.

3. In children older than 8 years after cochlear implantation, there was no statistically significant difference in the values of the parameters Way, Area, AP, Lateral, AP/Lateral in the position with open and closed eyes in comparison with children with normal hearing.

4. There were no statistically significant differences in the values of the Romberg Way, and Romberg Area parameters in the children of the studied groups.

5. The study showed no difference between the parameters of postural balance in children after cochlear implantation and children with sensorineural deafness in both age groups.

Name of parameter	Description	Units
Way	Describes the path of movement of the COP. Since the study time is set to a constant number, this parameter is characterized as the speed of COP	cm/s
Area	Marks the area and describes the variations in COP during the study	cm^2/s
Antero-Posterior (AP)	The resulting anteroposterior center of gravity vector (the length of the anteroposterior COP shifts during the study)	cm/s
Lateral	The resulting amplitude vector of the lateral displacements of the center of gravity (the length of the lateral displacements of the center of gravity during the study)	cm/s
AP/Lateral	The ratio of the anterior–posterior and lateral balance components of the subject. It reflects the general dominance of the direction of the gravitational amplitude	—
Romberg Way	The ratio of the Way values obtained in the study with the patient’s eyes open and closed	—
Romberg Area	The ratio of the Area values obtained in the study with the patient’s eyes open and closed	—

Table A1.

Technical terms used in manuscript.