Static Balance Performance and Sensory Integration Abilities of

Children with Dyslexia and Developmental Coordination Disorder

M. Nunzi

, F. Sylos Labini

3,4

, A. Meli

, S. Baldi

, D. Tufarelli

and C. Di Brina

Department of Mental Health (Child Neuropsychiatry), ASL of Viterbo, Italy

ENT Rehabilitation Unit, San Raffaele Pisana Scientific Institute Tosinvest Sanità, Via della Pisana, Rome, Italy

Laboratory of Neuromotor Physiology, IRCCS Fondazione Santa Lucia, Rome, Italy

Center of Space BioMedicine, University of Rome Tor Vergata, Rome, Italy

Keywords: Dyslexia, Developmental Coordination Disorder, Sensory Organization Test, Balance.

Abstract: Introduction: Postural dysfunctions are described in Developmental Disorders: the static balance deficit is

one of the major features of Developmental Coordination Disorder (DCD) and is reported in Dyslexic

Children. With computerized dynamic posturography (CDP) balance can be assessed objectively. The

primary aim of this study was to assess the postural function in DCD and Dyslexic in comparison with a

Control Group (CG) using CDP.

Subjects and Methods: Forty-seven children (29 males e 18 females) were assessed using all the six

conditions of the Sensory Organizing Test (SOT). 18 CG children (mean age 9.66 ± 1.96 years), 15

Dyslexic children (mean age 9.78 ± 1.09 years) and 14 DCD children (mean age 8.35 ± 1.79 years) were

included.

Results: DCD had poorer balance measured with the SOT score in every condition (p<0.05) except in SOT

3 (p= n.s.) compared to the CG. Dyslexic children had a good postural control compared to the CG, except

in SOT 5 (p = 0.02).

Conclusions: CDP showed that the DCD group had, as expected, a poorer balance than DD and CG. It is

possible to differentiate Dyslexics from the CG only in SOT 5, indicating that the postural disturbance of

this group is probably of primarily central vestibular origin. The somatic-sensory input had the same

influence on balance function in the three groups.

1 INTRODUCTION

The sensory integration is a physiological process in

selecting and combining appropriate sensory

information from somatosensory, visual and

vestibular systems. The Sensory Organization Test

(SOT) of the Computerized Dynamic Posturography

(CDP), is an objective measure of sensory

integration during balance performances. SOT

evidences more data and information than clinical

tests, using an objective analysis of balance function

(Nashner, 1997).

SOT analysis can help to identify the cause of

instability and the patient’s balance strategies

(Nashner, 1997; Prieto et al., 1996). But few studies

adopt CDP on Developmental Disorders in children.

Balance problems are described in children with

Developmental Dyslexia (DD) and Developmental

Coordination Disorder (DCD): whereas balance

impairment is a common feature and a "core"

symptom in DCD (Fong and Tsang, 2012), few

studies have investigated whether deficits in

multisensory integration may contribute to poor

standing balance in children with DCD

(Deconinck

et al., 2008). Geuze (2005) claims that under normal

conditions, static balance control is not a problem

for these children. For the majority of them, this

problem seems not to be due to greater dependence

on vision.

Moreover experimental studies resulted in the

general conclusion that DCD children had deficits in

standing balance control in conditions that included

reduced (in particular visual and vestibular) or

conflicting sensory signals (Fong and Tsang, 2012),

showing more postural sway in either one-legged

(Geuze, 2005) or two-legged stance (Przysucha and

Taylor, 2004). Converging evidence indicates that

cerebellar dysfunction contributes to the motor

problems of children with DCD. Objective

measurements confirmed these results evidencing, in

150

Nunzi, M., Labini, F., Meli, A., Baldi, S., Tufarelli, D. and Brina, C.

Static Balance Performance and Sensory Integration Abilities of Children with Dyslexia and Developmental Coordination Disorder.

In Proceedings of the 2nd International Conference on Computer-Human Interaction Research and Applications (CHIRA 2018), pages 150-155

ISBN: 978-989-758-328-5

a small sample of DCD, an altered pattern in the

SOT (Inder and Sullivan, 2005).

Literature on balance control in DD is

inconclusive: motor performance difficulties in DD

are attributed to a disorder in visual processing

(Stein and Walsh, 1997), in rapid information

processing (Tallal et al., 1993), and some studies

reported a postural control impairment and a

cerebellar deficit (Fawcett and Nicolson, 1999).

Nicolson et al. (1999), reported motor coordination

and balance deficits in dyslexic children population.

Other authors suggested that the balance impairment

was not strictly correlated with dyslexia but also

with other types of developmental disorders ( such

as comorbidity with Attention Deficit/Hyperactivity

Disorder (ADHD) (Raberger and Wimmer, 2003).

These opposite findings in the literature on the

argument could be influenced by differences in the

assessing processes: the use of different tasks in

evaluating balance, such as measuring the balance

only on the right or left foot (Stoodley et al., 2005),

the use of subjective measures of postural control

(Fawcett and Nicolson, 1999) and the evaluation of

dyslexic children only in the "eyes open" condition

(Moe-Nilsen et al. 2003).

The aim of this study was to assess postural

control of a DCD sample through the objective

measure of CDP, and to compare their balance

performances with DD children without co morbid

attention deficits and with a matched CG.

2 METHODS

Forty-seven children participated in the study. All

participants demonstrated adequate familial

environment, middle socio-economic status and

Wechsler Intelligence Scale for Children Revised

over 90. No child had attention-deficit disorder,

epilepsy, mental retardation, cerebral palsy,

psychiatric disorders, or other neurological signs,

congenital malformations, or phoniatric alterations,

neither peripheral vestibular disorder and inner ear

disease as referred by the anamnesis and the clinical

evaluation. Subjects were divided in three groups: a

control group (CG) of 18 children (mean age 9.66 ±

1.96 years), a group of 15 dyslexic children (DD)

(mean age 9.78 ± 1.09 years) and a group of 14

DCD children (mean age 8.35 ± 1.79 years). The

diagnosis of DD and DCD was done according to

DSM-IV criteria. Children included in the DCD

group scored below the 15th percentile on the total

impairment score on the Movement-ABC

standardized test. Written informed consent to

participate in the study was obtained by parents of

all children. The study was approved by the IRCSS

San Raffaele, Hospital of Rome Pisana, Institutional

Internal Review Board. Postural control function

was assessed by SMART EquiTest 8.0 (NeuroCom

Int., Inc., Clackamas, OR, USA) instrument, using

static and dynamic CDP. This instrument has been

adopted as the only method to isolate the functional

contributions of vestibular inputs, visual inputs,

somato-sensory inputs, central integrating

mechanisms, and neuromuscular system outputs for

postural and balance control (Black, 2001) and the

instrument meets the testing standard for CDP set by

the American Academy of Otolaryngology-Head

and Neck Surgery and the American Academy of

Neurology. All subjects were evaluated using the

Sensory Organization Test (SOT) of Dynamic

Posturography (Equitest© Neurocom). The SOT

analyses the postural control and the contributions of

different sensory systems to balance control during 6

conditions, each test condition was examined three

times for 20 seconds with a 20-second break

between tests. Six different conditions (A-F) were

used in order to examine the subject’s balance

control performance under different sensory

conditions that we will call C1, C2, C3, C4, C5, C6

(Table 1, Table 2).

The force plate and visual surround are “sway

referenced” so that they can move to follow the

anterior-posterior sway of the subject. The six

conditions of the SOT are called Equilibrium Scores

(ES), that are obtained by comparing the maximum

anterior-posterior CoG displacements to a theoretical

maximum displacement. The ES ranges between 0

and 100. Lower ES indicate increased body sway

peak-to-peak amplitudes. The score of “0” was

recorded if the subject falls, touches, or gripes

reference for protecting. Nobody sway results in a

perfect score of “100.” The Composite Equilibrium

Score (CS) is a synthetic index of equilibrium and is

a mean value from the scores of all six conditions.

The CS is evaluated as a weighted average of one

subject’s equilibrium scores from six conditions of

the SOT: CS={ES(1)+ ES(2) +3[ES(3)+ ES(4)

+ES(5)+ ES(6)]}/14.

Statistical Analysis. We used one-way ANOVA to

evaluate differences between groups in mean

Composite Score, Condition Scores and in Sensory

Analysis Scores. We performed the multiple

comparison of the means using the post-hoc Tukey-

Kramer test. Pearson correlation coefficients were

used to analyze the relationship between age and

Condition Scores. Reported results are considered

significant for p < 0.05.

Static Balance Performance and Sensory Integration Abilities of Children with Dyslexia and Developmental Coordination Disorder

151

Table 1: Sensory input conditions during SOT.

Sensory condition description

Accurate Sensory

Sensory loss

Sensory conflict

C1. (A) Eyes open, fixed support

Visual, vestibular,

somatosensory

None

C2. (B) Eyes closed, fixed support

Vestibular, somatosensory

Visual

None

C3. (C) Eyes open, sway-referenced visual

surround

Vestibular, somatosensory

None

Visual

C4.(D) Eyes open, sway-referenced

platform

Visual, vestibular

None

Somatosensory

C5. (E) Eyes closed, sway-referenced

platform

Vestibular

Visual

Somatosensory

C6.(F) Eyes open, sway-referenced visual

surround and platform

Vestibular

None

Visual, somatosensory

Table 2: Six conditions (A–F) of SOT.

Figure 1: Composite Score and Condition Scores. Average (+SD) composite and condition scores across different groups

(Control: control group, DD: children with Developmental Dyslexia, DCD: children with Developmental Coordination

Disorder). Asterisks denote significant (Tukey-Kramer post-hoc test p < 0.05) differences.

3 RESULTS

The data showed significant differences in the

results of SOT among groups (p-value < .001)

(Fig.1); the 40% of DD children and 93% of DCD

children had a lower CS, than the mean value of CG.

The results of our CG were similar to that reported

in literature (Steindl et al., 2006).

The DD group had scores similar to control

values in all conditions, except for condition 5.

The mean C5 score of DD was similar to the

mean C5 score of DCD group and was significantly

CHIRA 2018 - 2nd International Conference on Computer-Human Interaction Research and Applications

152

Figure 2: Sensory Analysis of Control group, DD and DCD groups. Asterisks denote significant (Tukey-Kramer post-hoc

test p < 0.05) differences.

poorer than control group (p-value = .020).

Furthermore, 53% of DD children had a lower score

in condition 5 than control children. The DCD

children had significantly worse results than the

other two groups in all conditions (p-value < .05)

except for Condition 3. In this condition there were

no significant differences among groups (p-value =

.524)

Moreover, 71% of DCD children had a lower

score in condition 5 than control group. Correlations

between age and condition scores were not found

(Pearson correlation coefficient < .60). The results of

sensory analysis showed that the somato-sensory

input had the same influence on balance function in

the three groups. Nevertheless in the DCD children

the use of visual and vestibular information in

maintaining balance was significantly less efficient

than controls. The DD children had a similar result

to DCD group for the vestibular afference, but a

normal use of visual information in maintaining

equilibrium (Fig.2).

4 DISCUSSION

Our results showed balance performances and

different sensorial patterns in two different groups of

children with Developmental Disorders. The

strategies of DD and DCD groups, during balance

tasks, were different from those adopted by CG. We

found a significantly lower balance control of DCD

group than other groups in upright standing

condition (condition 1 and condition 2), even if their

poorer performances were in tasks with sway-

platform (condition 4, condition 5 and condition 6).

These findings are consistent with previous literature

reporting a larger dependency of DCD children on

vision and difficulties in integrating visual and non-

visual information (Wann et al., 1998). Our DCD

children perceived a sway visual surround as a

negligible input in maintaining balance, their scores

were normal in conditions with visual reference

sway (condition 3). This result indicated a normal

ability to discriminate a destabilizing visual input,

which is a cortical function. Geuze (2005) found that

an improvement in conflicting sensory inputs can

occur with eyes open. It seems that the unavailability

of an important sensory information such as visual-

perception can influence the quality of postural and

balance control in DCD Children. Postural control

problems may possibly be associated with

difficulties to re-weight sensory information in

response to environmental demands (Deconinck et

al., 2008).

In summary, we observed poorer static postural

control ability in children with DCD compared with

Controls and the vestibular system failed to

effectively integrate sensory information of

insufficient and/or inaccurate visual or somato-

sensory perception, thus leading to loss balance.

However in the visual conflict they could maintain

balance (condition 3).

Our DD children showed significant impairment

of balance control with increasing task difficulty

(i.e., reduction or conflict of sensory inputs) which is

consistent with others findings: some motor

impairment in relatively complicated balance tasks

(dual-tasks) and in presence of conflicting sensory

inputs (Huxhold et al., 2006). Balance performances

of our sample showed that DD children had a normal

composite score. Balance function in DD group was

better than DCD group, however in DD children we

found higher incidence (53%) of poor balance

performances in complex tasks (condition 5). The

poor balance performance of DD children in this

task is associated with the visual exclusion and to

grounding on vestibular information (somato-

sensory conflict); DD children had a lower

Static Balance Performance and Sensory Integration Abilities of Children with Dyslexia and Developmental Coordination Disorder

153

performance with eyes closed. These findings are in

contrast with findings from other authors reporting

lower balance performances of dyslexic children in

eyes open tasks (Moe-Nilssen et al., 2003; Stoodley

et al., 2005) or normal postural stability in both

conditions (Brown et al., 1985). A possible

explanation of these differences can resides in the

balancing task proposed by these authors. It is well

established that postural stability is task dependent

(Cho and Kamen, 1998).

The stance position with eyes open could be too

easy for DD children; these tasks may not be able to

evidence balance control impairment in patients with

a normal somato-sensory and visual afferents. These

children in fixed surface with eyes open condition

use information from somato-sensory and visual

systems to maintain upright position.

Ramus and colleagues, who found evidence of

impaired balance control in dyslexic children,

related it to an altered vestibular pattern (Ramus et

al., 2003). Our data similarly indicated poor

vestibulo-spinal postural control.

Several studies evidenced the activity of

cerebellum and basal ganglia in sensory-motor

integration function and in learning, furthermore,

their role is still unclear (Waber et al., 2004).

5 CONCLUSION

In conclusion, this study, in accordance with

previous reports, provided evidence suggesting that

DCD and Dyslexic children have impaired postural

stability compared to children of similar age.

The small sample size is the main limitation of

this study and these findings could be explored

further with a larger sample. In agreement with the

hypothesis of sensori-motor deficit in DD and DCD,

these children could suffer of a sensory multimodal

integration difficulties.

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