Motor Development of Deaf Children With and Without Cochlear Implants

Transcription

1 Motor Development of Deaf Children With and Without Cochlear Implants Freja Gheysen Ghent University Gerrit Loots Vrije Universiteit Brussel, Ghent University Hilde Van Waelvelde Ghent University The purpose of this study was to investigate the impact of a cochlear implant (CI) on the motor development of deaf children. The study involved 36 mainstreamed deaf children (15 boys, 21 girls; 4- to 12-years old) without any developmental problems. Of these children, 20 had been implanted. Forty-three hearing children constituted a comparison group. Motor development was assessed by three standardized tests: the Movement Assessment Battery for Children, the Körperkoordinationstest für Kinder, and the One-leg standing test. Results showed that the hearing children performed on average significantly better than the deaf children (whether or not using a CI). Regarding the use of a CI, there was only a significant difference on one subtest between both groups, although there was a nonsignificant trend for the deaf 1CI group to score somewhat worse on average than the deaf CI group. This led to some significant differences between the hearing group and the deaf 1CI group on measures requiring balance that did not hold for the hearing/deaf CI comparison. Although this study could demonstrate neither a positive nor a negative impact of CI on balance and motor skills, the data raise the need for further, preferably longitudinal, research. No conflicts of interest were reported. Correspondence should be sent to Gerrit Loots, Faculty of Psychology and Educational Sciences, Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium ( gerrit.loots@vub.ac.be). In most cases, deafness is caused by the absence or degeneration of sensory hair cells in the cochlea, severing the connection between the peripheral and central auditory systems. The cochlear implant (CI) bypasses the hair cells by delivering electrical signals directly to the surviving elements of the auditory nerve (Niparko, 2000). Over the past two decades, cochlear implantation has become a widely accepted device in the rehabilitation of deaf children and has been characterized by rapid and continuous evolution. While the technology of the CI advances, the candidacy for these devices continues to broaden and the age at implantation is decreasing. Although different factors contribute to an individual child s success, a large body of reports is now available showing positive outcomes on the development of auditory skills, speech reception, and production (Balkany et al., 2002; Copeland & Pillsbury, 2004; Niparko & Blankenhorn, 2003). Auditory performance in pediatric cochlear implantation has been the subject of much research, but very limited work has been done on the repercussions of a CI on motor development. This is at least surprising because it is commonly accepted that children with hearing losses are vulnerable with regard to motor development. From birth onwards, auditory stimulation directs and intensifies visual orientation behavior. The infant s earliest responses to auditory stimuli include the visual-motor behavior of moving the eyes or head to localize sound. Therefore, it has been suggested that the lack of early auditory input could contribute to motor delays in deaf and hard-of-hearing children (Savelsbergh, Netelenbos, & Whiting, 1991). Several studies of motor skills in deaf children reported deficits in balance, general dynamic coordination, visual-motor skills, and ball catching abilities and cite clear differences in reaction times and speed of movements (Savelsbergh et al., 1991; Siegel, Marchetti, & Tecklin, 1991; Wiegersma & Van der Velde, 1983). Recently, Horn, Pisoni, and Miyamoto (2006) have suggested that these findings of atypical motor Ó The Author Published by Oxford University Press. All rights reserved. For Permissions, please journals.permissions@oxfordjournals.org doi: /deafed/enm053 Advance Access publication on October 27, 2007

2 216 Journal of Deaf Studies and Deaf Education 13:2 Spring 2008 development in deaf children may not be generalized. They claimed that earlier studies had potential confounding factors that might have been responsible for the delays in motor skills in deaf children, such as differences in types of schooling, presence of neurological problems, and differences in ages at diagnosis of deafness and onset of intervention. Two studies reported preimplant motor scores of prelingually deaf infants and children that fell within the typical range of variation found in hearing children (Horn, Pisoni, Sanders, & Miyamoto, 2005; Kutz, Wright, Krull, & Manolidis, 2003). Furthermore, Lieberman, Volding, and Winnick (2004) did not find significant differences in motor development between deaf children with deaf parents and those with hearing parents. Yet, they stressed the fact that environmental factors like type of schooling and parental involvement in physical activity seemed to influence motor development in deaf children and probably contributed to the relatively high performance levels of the participants in their study. Attending schools providing an early physical intervention and a structured physical education program designed to meet the specific needs of deaf children can contribute to a better acquisition of motor skills. Possible explanations of observed motor deficits in deaf children are described by Wiegersma and Van der Velde (1983) in four categories: (a) organic factors: associated vestibular or neurological defects; (b) sensory, auditory deprivation; (c) verbal, language deprivation: a lack of verbal representations of motor skills, verbal-conceptual strategies to support execution; and (d) emotional factors: a lack of self-confidence, overprotection, or neglect from the parents can cause the deaf child to be less willing to explore the environment. Based on the aforementioned possible determinants of delays in motor development of deaf and hard-of-hearing children, we state two contradictory hypotheses with regard to the impact of cochlear implantation on motor skills: 1. CI may have a positive effect on motor performance because of the auditory input and stimulation obtained from the CI and the observed positive outcome on self-confidence (Incesulu, Vural, & Erkam, 2003) and language development. Using the Reynell Developmental Language Scales, evaluating both receptive and expressive language skills, several studies demonstrated that CIs have a significant beneficial effect on the development of spoken language in deaf children (Miyamoto, Houston, Kirk, Perdew, & Svirsky, 2003; Robbins, Svirsky, & Kirk, 1997; Svirsky, Robbins, Kirk, Pisoni, & Miyamoto, 2000). The study of Schlumberger, Narbona, and Manrique (2004) tends to agree with this hypothesis. They supported early implantation because it enabled good verbal development and might also improve nonverbal (motor) capacities. Also the results of Buchman, Joy, Hodges, Telischi, and Balkany (2004) lend some support to this hypothesis. Their study indicated that deaf persons who received unilateral CI s experienced substantial improvements in both subjective and objective measures of vestibular and balance function. 2. On the other hand, because of the close relationship of the cochlea and the vestibular receptors, CI carries with it the potential risk for vestibular damage caused by surgical trauma or indirect electrical stimulation of the vestibular nerve with resultant vestibular dysfunction and balance problems. Because of the complexity of balance control, diagnosing a balance problem and its specific cause can be difficult. Maintaining balance relies on the interaction of different components including visual, vestibular, and proprioceptive input. Using the Postural Control test, Suarez et al. (2007) investigated how deaf children with normal and abnormal vestibular responses used these different components of sensory information for postural control. Deaf children with vestibular loss could not maintain the standing position when the visual information was removed and the somatosensory input was modified. Yet, when visual and somatosensory input was enabled, these children showed values of postural control similar to those of deaf children with normal vestibular function as well as those of hearing children. This suggests a compensation process whereby input from proprioceptive, visual, and other sensory systems substitute for the absent peripheral vestibular input. These authors reported no effect of hearing habilitation with a unilateral CI on the

3 observed sensory organization strategy: the implanted children did not show a significant difference in postural control with the implant turned on and turned off. Significant histopathologic changes in the vestibule after CI have been noted by Tien and Linthicum (2002). In their study, the overall incidence of vestibular damage after cochlear implantation was 54.50%. Numerous studies have also attempted to characterize the effects of CI on the vestibular system using different specific vestibular tests. The results of these studies are however conflicting. In a recent study of Jin, Nakamura, Shinjo, and Kaga (2006) using vestibularevoked myogenic potentials, 7 of 12 children (58.30%) showed a reduction in saccular function after CI. On the other hand, Migliaccio, Della Santina, Carey, Niparko, and Minor (2005) studied pre- and postoperative changes in semicircular canal function revealed by vestibule-ocular reflex responses and found no significant (,10%) loss of vestibular function due to CI. Buchman et al. (2004) summarized the results of 22 published electronystagmography studies. In these studies, 71 (38%) of 186 patients demonstrated changes in caloric response after CI at various intervals of postimplantation. These findings indicated mostly reductions in the caloric response as compared with preoperative values. Beside possible deficits in vestibular function, also postoperative vestibular symptoms such as dizziness and vertigo have variably been reported to occur after CI (Fina et al., 2003; Ito, 1998; Kubo, Yamamoto, Iwaki, Doi, & Tamura, 2001; Steenerson, Cronin, & Gary, 2001). Fortunately, vestibular symptoms after CI are usually transient, can be well treated by vestibular therapy, and resolve completely in time. Based on the aforementioned findings, CI may have a negative outcome on motor performance of deaf children caused by vestibular damage and associated problems with postural stability. The aim of this study is to investigate the possible consequences of cochlear implantation on the motor abilities of deaf children and to find evidence for one of the two hypotheses. A better understanding of whether or not a CI significantly affects motor function is important for preoperative counseling and rehabilitation after implantation. Method Motor Development and Cochlear Implantation 217 Permission for the study was given by the local ethics committee. A written informed consent was obtained from the children s parents. Also all children were counseled and informed regarding study participation. Participants In Flanders (Belgium), deaf children s education is organized by six primary schools for the deaf. Most deaf children without additional disabilities or developmental problems are in mainstream education programs. They attend regular schools in their local environments that use spoken language only and receive individual support from teachers and/or speech therapists from one of the schools for the deaf for 4 hr a week. All deaf children between 4- and 12-years old who participated at those mainstream education programs and who had a hearing loss 90 db, without cognitive developmental problems, cerebral palsy, or orthopedic disorders (N 5 116), were invited to participate in the study. Children who attended the special education programs in the schools for the deaf were not invited to participate because many of these children have multiple disabilities that may explain motor developmental disorders. Because of legal privacy reasons, the teachers and speech therapists from all six deaf schools who were involved in the mainstream education programs prepared an invitation letter for parents and children to participate in the study that required them to give their names and addresses to the researchers. Due to this rather impersonal procedure and because this group of children receive many requests for taking part in research programs, only 36 of the 116 children who were invited, participated in the testing (15 boys, 21 girls; age range 4 years, 6 months 12 years, 8 months; M 5 9 years, 1 month; SD 5 2 years, 3 months). A questionnaire was developed to record the following characteristics: date of birth, medical conditions, level of hearing presence of a CI, age at implantation, cause of deafness, and IQ. The deaf group included 16 children without and 20 children with CIs. The mean age at receiving a CI was 3.79 years (SD ). On average, children had their CI for a period of 4 years (SD ) at the time of motor assessment.

4 218 Journal of Deaf Studies and Deaf Education 13:2 Spring 2008 Table 1 Characteristics of deaf children with (Cl1) and without (Cl ) cochlear implants Group Cl1, n 5 20 Group Cl, n 5 16 Age, M (SD) 8 years; 6 months (2 years; 1 month) 9 years; 9 months (2 years; 3 months) Gender, n (%) Boys 9 (45) 6 (38) Girls 11 (55) 10 (62) Age of deafness, n (%) Congenital 13 (65) 5 (31),3 years 1 (5) 3 (19).3 years 0 2 (13) Unknown 6 (30) 6 (37) Etiology of deafness, n (%) Unknown 15 (75) 11 (69) Genetic 2 (10) 2 (13) Medication 0 1 (6) Syndrome 1 (5) 1 (6) Preterm 0 1 (6) Meningitis 1 (5) 0 Cytomegalia 1 (5) 0 Note. Numbers in parentheses 5 percentages. A comparison of both groups showed no differences for age (t(34) ; p 5.100) and gender (v 2 (1) 5.206; p 5.650). The group of children with CI consists of more children with congenital hearing losses (65%) compared to those without CI (31%). Although we have to be cautious about this difference, because for one-third of the children in each group the age at onset of the hearing loss is unknown (see Table 1), it will be important to consider this when discussing the results. The group of deaf children was compared for age and gender with a group of hearing children. This comparison group comprised 43 children (15 boys, 28 girls) with ages ranging from 4 years 2 months to 12 years 7 months (M 5 8 years, 8 months; SD 5 2 years, 6 months). No differences for age (t(77) 5.861; p 5.392) and gender (v 2 (1) 5.383; p 5.536) were found between both groups of hearing and deaf children. Procedure Children were tested individually on motor skills in a quiet environment in their schools. Three examiners assessed all children. These three examiners were trained together in the assessment procedures by the third author. They also received training in communication with deaf children. Two examiners were lastyear students in physical education and the other a last-year student in special needs educational psychology. All deaf children grew up in an oral communication setting and used spoken language only for communication. Before each assessment, the regular schoolteacher of the child informed the examiners about the child s specific needs for optimally understanding test instructions. Measures Movement Assessment Battery for Children. The Movement Assessment Battery for Children (M-ABC) is a standardized motor test developed by Henderson and Sugden (1992) for the identification and evaluation of children with mild to moderate motor impairments. It contains two assessment instruments: a performance test and an observational checklist. In this study, the Dutch validated version of the performance test was used (Smits-Engelsman, 1998). The test accommodates 4 age bands for children with ages ranging from 4- to 12-years old. The test evaluates eight tasks grouped under the headings manual dexterity (three items), ball skills (two items), static balance (one item), and dynamic balance (two items). On each item, quantitative raw scores are converted to normative scores ranging from 0 to 5. The scores of the different items are combined to produce a total score ranging from 0 to 40, with higher scores indicating poorer performance. The test score can be transformed into a percentile score, but not into a standard score. Henderson and Sugden (1992) investigated the reliability of the total scores in terms of their consistency over a 2-week period and found a 97% agreement for age 5, 91% for age 7 and 73% for age 9. More recent studies on the reliability and validity also support the use of the M-ABC as a measure of motor ability in children (Croce, Horvat, & McCarthy, 2001; Leemrijse, Meijer, Vermeer, Lambregts, & Adér, 1999). Körperkoordinationstest für Kinder. The Körperkoordinationstest für Kinder (KTK), a German test

5 developed in 1974 by Kiphard and Schilling, is a standardized normative instrument measuring gross motor coordination for children between 5- and 14-years old. The KTK consists of four tasks that demand the use of dynamic balance: (a) walking backward on beams of decreasing width, (b) hopping on one leg over an increasing number of foam plates, (c) jumping laterally to and fro with both legs, and (d) moving across the floor by stepping from one plate on a second plate, then relocating the first plate, then taking the next step, etc. Performance on the KTK is described by a standardized motor quotient (MQ) with a mean of 100 (SD 5 15). Kiphard and Schilling (1974) reported a test retest correlation coefficient between 0.80 and 0.96 for the raw scores of the four KTKtasks and 0.90 for the total MQ-scores. The KTK is therefore considered to be a reliable instrument to measure dynamic body coordination. Previous studies, however, showed that the norms of the KTK were not applicable for a group of Dutch children. A validity study comparing the Movement-ABC and the KTK (Smits-Engelsman, Henderson, & Michels, 1998) concluded that the KTK identified more children with motor problems in the Dutch population. Therefore, we only used the KTK to compare the different groups of children involved in this study. One-leg standing test. The one-leg stance is a frequently used clinical tool by physical and occupational therapists for assessment of balance. It assesses postural steadiness in a static position by a quantitative measurement, which is the number of seconds a person can maintain the one-leg standing position. Atwater, Crowe, Deitz, and Richardson (1990) found that the OLS with eyes open or closed has good interrater reliability (Spearman s r ) and fair to good test retest reliability (Spearman s r ). Liao, Mao, and Hwang (2001) reported that the OLS with eyes open was highly reliable in children with cerebral palsy (ICC 0.99). In this study, all children performed a standardized protocol of the OLS test. The children were instructed to stand on one leg for as long as possible with a maximum of 20 s each trial. Before testing, they were allowed to practice once with eyes open on each leg during 10 s. Then, the test was performed three times with eyes open and three times with eyes closed, first on the preferred leg followed by the nonpreferred leg. The children got assistance from the investigator to take the initial position and were instructed to stand as long as possible on one leg without touching the floor or the standing leg with the lifting leg. The scores of three trials were summed for left and right leg both with eyes open and eyes closed. Results Motor Skill Performance and Hearing Status The comparison group had a mean total M-ABC score of 5.65, corresponding to a percentile score of 40. This mean score was not significantly different (p 5.11) from the standard group when compared by means of a one-sample t-test with the 50th percentile of the M-ABC (5score 4.5). The deaf children had a mean M-ABC score of 10.07, corresponding with the 15th percentile of the M-ABC. Table 2 compares motor skill performances of both groups of hearing and deaf children. Significance testing was performed by the use of independent t-tests. Because of the large number of comparisons to be performed, a Bonferroni correction was used to set Table 2 Mean scores, standard deviations (in parentheses), and comparison (t-tests) of motor skill performances of both groups of hearing and deaf children Motor test M-ABC a Motor Development and Cochlear Implantation 219 Hearing (n 5 43) Deaf (n 5 36) p Manual dexterity 1.26 (1.65) 2.54 (2.86).020* Ball skills 2.24 (2.72) 3.61 (3.11).040* Balance 2.17 (2.68) 3.89 (3.25).012* Total score 5.65 (4.63) (7.09).002** KTK MQ (13.00) (16.69).115 MQ (13.56) (17.51).007** MQ (14.02) (17.64).497 MQ (12.01) (14.82).068 Total score (13.53) (17.48).057 OLS Eyes open (26.03) (34.51).002** Eyes closed (24.31) (19.89).000** Total score (45.35) (49.09).000** a Higher scores mean poorer functioning on the M-ABC. *p,.05, **p,.008 (Bonferroni correction).

6 220 Journal of Deaf Studies and Deaf Education 13:2 Spring 2008 Time in seconds Deaf Hearing status significance at p.10/ , two-tailed, in an effort to maximize sensitivity to any possible differences in motor skills between both groups of children. Also, significance at p.05, two-tailed, was cautiously taken into consideration as a trend. A two group multivariate analysis of variance was not used because the homogeneity of covariance matrices was not guaranteed and the homogeneity of variance assumption was not fulfilled for all dependent variables. Motor performances of hearing children were significantly better for the total score of the M-ABC and all scales of the OLS. Also, the hearing children showed a trend toward better manual dexterity, ball skills, and dynamic and static balance on the scales of the M-ABC. Although not significantly, hearing children also seemed on average to show better dynamic balance skills on all scales of the KTK, compared to the group of deaf children. Mainly on the One-leg standing test (OSL), hearing status had a significantly important impact. As shown in Figure 1, deaf children were far less skilled than their hearing peers in keeping balance when standing on one leg. Especially with eyes closed, keeping balance was not evident for the group of deaf children. Motor Skill Performance and CI Hearing Total score Eyes open Eyes closed Figure 1 Comparison between both groups of children for static balance on the One-leg standing test (OLS). To examine the impact of a CI on the motor performances of the deaf children, the three groups of children were compared for each motor skill test by the use of ANOVA s. However, the homogeneity of variance assumption was not fulfilled for four variables, M-ABC: manual dexterity and total score; OSL: scores on the subtests eyes open and eyes closed. Because group sizes were sharply unequal and the large sample variances were associated with the small group sizes (see Table 2), the F statistics became too liberal, and the risks of falsely rejecting the null hypothesis increased beyond acceptable levels (Stevens, 1996). Because of this, the nonparametric Kruskal Wallis test was used to compare groups for those variables. Significance was set at p.05. The mean total M-ABC score of the children with a CI was corresponding with the 14th percentile and the mean total M-ABC score of the children without a CI was 9.19 corresponding with the 19th percentile of the standardization group. Nearly all subtest and test scores showing significant differences among the three groups of children are examining dynamic and static balance (see Table 3). Because of unequal group sizes, Hochberg s GT2 post hoc procedure was used for pairwise comparisons, and the Games-Howell procedure was used in the case of unequal population variances. The group of hearing children showed better balance than deaf children with CIs on the M-ABC balance subtest (p 5.044), the KTK walking backward (MQ1) subtest (p 5.019), and the OLS total score (p,.001), eyes open subtest (p 5.008) and eyes closed subtest (p,.001). On the other hand, no differences were found between the hearing group and deaf children without a CI, except for the KTK jumping on one leg (MQ2) subtest (p 5.002). For this subtest, deaf children without a CI performed significantly lower than the children of the hearing comparison group. Also, no significant differences were found between both groups of deaf children with and without a CI, except for only one subtest. Deaf children without a CI had better balance than children with CIs on the KTK walking backward on beams (MQ1) subtest (p 5.033). Discussion Cochlear implantation to restore hearing in children with profound sensorineural hearing loss is being

7 Motor Development and Cochlear Implantation 221 Table 3 Comparison of three groups: hearing children, deaf children with cochlear implants (Cl1), and deaf children without cochlear implants (Cl ) Motor test Hearing (n 5 43) Cl1 (n 5 20) Cl (n 5 16) p M-ABC a Manual dexterity 1.26 (1.65) 3.05 (3.30) 1.91 (2.12).190 b Ball skills 2.24 (2.72) 3.55 (3.31) 3.69 (2.93).123 Balance 2.17 (2.68) 4.18 (3.60) 3.53 (2.83).036* Cl1,H Total score 5.65 (4.63) (7.85) 9.19 (6.15).012* b Cl1,H KTK MQ (13.00) (13.17) (18.42).011* Cl1,H, Cl MQ (13.56) (14.74) (19.34).003* Cl, H MQ (14.02) (20.55) (13.61).663 MQ (12.01) (17.59) (10.95).188 Total score (13.53) (18.72) (16.37).160 OLS Eyes open (26.03) (37.16) (29.81).001* b Cl1,H Eyes closed (24.31) (11.93) (24.72).000* b Cl1,H Total score (45.35) (45.31) (49.77).000* Cl1,H a Higher scores mean poorer functioning on the M-ABC. b Nonparametric Kruskal Wallis test was used. *p.05. performed with increasing frequency. With ever broadening criteria for CI candidacy, the younger age at implantation and the development of bilateral CI, understanding the risk of CI-induced motor developmental problems takes on an increasing importance. Our first results on motor development confirm previous studies that deaf children demonstrate motor delays compared with hearing peers (Savelsbergh et al., 1991; Schlumberger et al., 2004; Siegel et al., 1991; Wiegersma & Van der Velde, 1983). Comparing the deaf and hearing groups, hearing children performed on average significantly better than the deaf children on six of the nine subtests and on two of the three total test scores. Especially on balance-related tasks, the group of deaf children in our study showed more difficulties. It is not clear whether these differences are due to auditory functioning or other effects of the etiologies of the hearing loss. However, these findings of motor delays in deaf children are in contrast to the results reported by Kutz et al. (2003) and Horn, Pisoni, Sanders, et al. (2005). A potential cause of these differences in results may be the differences in test instruments used to measure motor development. In the study by Kutz et al. (2003) and Horn, Pisoni, Sanders, et al. (2005), motor development was assessed using the Vineland Adaptive Behavioral Scales. Unlike the tests used in our study, this is not a specific motor test but it consists of an interview format in which parents or caregivers of the children respond to questions concerning daily living skills, socialization, communication, and motor skills. As Horn, Pisoni, and Miyamoto (2006) suggested in a later study, this test is rather coarse and possibly biased on the part of the person who answers the items. Another possible confounding variable is the age at testing. In our study, the mean age of deaf children (9 years, 1 month) is quite higher than the participants in the studies mentioned before. Deaf children who are older and have experienced longer periods of auditory deprivation may be expected to demonstrate a more delayed motor development than younger deaf children with shorter periods with limited auditory input. Horn, Pisoni, and Miyamoto (2006) found evidence for this hypothesis: fine motor skills, in contrast to gross motor skills, tended to be more delayed when the prelingually deaf children got older. With respect to the impact of CI on the motor system, this study could not find clear evidence for one of the two hypotheses. For only one subtest, a significant difference was found between both groups

8 222 Journal of Deaf Studies and Deaf Education 13:2 Spring 2008 of deaf children: the children without CI performed better on the first item of the KTK walking backwards on beams, although there was a nonsignificant trend for the deaf children with CI to score somewhat worse on average than the group of children without CI. This led to the identification of some significant differences between the hearing group and the group of children with CI that did not hold for the comparison between the hearing group and the group of deaf children without CI. A number of these differences were on measures requiring balance, raising the need for further research in this area. These results are not consistent with earlier findings put forward by Schlumberger et al. (2004). In their study, the hearing children also had better balance than the children with deafness. However, when balance was compared separately for the children younger and older than 7 years old, the hearing group had better balance than the children with deafness without CI, but no significant difference was found between the hearing group and the children with CI in either age range, something that is in conflict with our results. Schlumberger et al. (2004) suggested that the motor retardation, observed in the deaf subjects, can be attributed to the auditory deprivation. Furthermore, they claim that the damaged auditory input should be restored as early as possible because an early CI might improve nonverbal (motor) abilities. Based on the results of this study, we cannot agree with this statement. Although it could not be demonstrated that children with CI clearly differ from children without CI in their motor development, we can state that the implanted children certainly did not perform better than the children without implant. One factor that may have contributed to the absence of any significant effect of cochlear implantation is the small sample sizes. Twenty and sixteen children in each of the deaf groups are relatively low numbers and thereby limited the power of the statistical tests. It is not inconceivable that broader sampling might find significant differences between children with and without CI. Although the reasons for the differences between our study and the study of Schlumberger et al. (2004) are not totally evident, differences between the participant groups (e.g., age at implantation, etiology of hearing loss), testing instruments, CI devices, and surgical procedures all may be important factors. In the study of Schlumberger et al., the children without implants had significant lower IQ-scores, performed more poorly on visual tasks, and were slower at certain tasks of the revised neurological examination for subtle signs as compared to the CI children. One might assume that these factors can contribute to the observed results. We acknowledge that also in our study, differences in characteristics among the two groups of deaf children may have influenced the findings. Although the age at onset of hearing loss is not known for 30% and 37% in the group with and without CI, respectively, more children without implant had an acquired form of deafness. This could mean these children had at least some exposure to auditory perception before deafness. One might assume that these children without CI had better motor skill performance because, as Savelsbergh et al. (1991) suggested, auditory stimulation has a positive influence on motor development of children. On the other hand, Horn, Pisoni, Sanders, et al. (2005) demonstrated that children with acquired causes of hearing loss showed lower motor scores than children with congenital causes. Because the data presented in our study are only postimplant measures of motor performance, we cannot confirm that both groups of deaf children were not nonequivalent prior to implantation. Controlling for confounding variables is needed to adequately assess the impact of cochlear implantation on the development of motor skills and specifically on balance performance. Future studies should therefore use a within-subject longitudinal design and obtain both pre- as well as postimplant data. Between the group of deaf children with CI and the group of hearing children, the most striking differences were found in the One Leg Standing (OLS) scores measuring static balance. The deaf children with an implant demonstrated clear balance problems in contrast to their hearing peers, something that could not be attributed to the deaf children without CI. The study of Buchman et al. (2004) indicated that the patients with CI experienced some substantial improvements in both subjective and objective measures of vestibular and balance function after CI surgery. Computerized dynamic posturography

9 (CDP) scores demonstrated improvements in postural stability with the device off and on. This observed positive effect of CI on postural stability is not consistent with the results in our study showing significant differences in balance between the CI group and the hearing group. Though some items in our study had the same purpose in measuring balance, our data cannot easily be compared with data obtained from CDP assessment. Unlike the CDP, the functional tests used in our study did not measure a sway angle in different sensory conditions. This can be confirmed by the study of O Neill, Gill-Body, and Krebs (1998) who demonstrated that posturography changes were not predictive of, nor often even directly correlated with, changes in functional performance. Conclusion The impact of a cochlear implantation on the vestibular function and/or motor development of deaf children is hardly investigated and not fully known. Some authors emphasize an improvement in vestibular function and motor development after receiving a cochlear implantation. Other researchers point to the potential risks of cochlear implantation for vestibular deficits, which can have a negative impact on motor development and performance of deaf children. The findings of the present cross-sectional study show that deaf children with a CI do not perform better on balance and motor skills than children without CI. However, due to the lower scores on balancing in the group of deaf CI children compared to those of both other groups of deaf and hearing children, we believe that further consideration must be given to the possibility that CI may affect the motor abilities of deaf children. If we wish to acquire a realistic picture of the repercussions of CI, the study of motor development of implanted children cannot be neglected and requires further investigation. Because it is difficult to control possible confounding factors and thus difficult to compare two groups of deaf children, our understanding is that in the future further studies with long-term follow up are needed to fully assess the risks of CI on motor development. We also recommend that these studies should test children at various pre- and postoperative intervals Motor Development and Cochlear Implantation 223 using standardized motor and vestibular tests together with a close investigation of etiology of hearing loss, age at implantation, scans of inner ear, etc. References Atwater, S. W., Crowe, T. K., Deitz, J. C., & Richardson, P. K. (1990). Interrater and test-retest reliability of two pediatric balance tests. Physical Therapy, 70, Balkany, T. J., Hodges, A. V., Eshraghi, A. A., Butts, S., Bricker, K., Lingvai, J., et al. (2002). Cochlear implants in children a review. Acta Otolaryngologica, 122, Buchman, C. A., Joy, J., Hodges, A., Telischi, F. F., & Balkany, T. J. (2004). Vestibular effects of cochlear implantation. Laryngoscope, 114, Copeland, B. J., & Pillsbury, H. C. (2004). Cochlear implantation for the treatment of deafness. Annual Review of Medicine, 55, Croce, R. V., Horvat, M., & McCarthy, E. (2001). Reliability and concurrent validity of the movement assessment battery for children. Perceptual and Motor Skills, 93, Fina, M., Skinner, M., Goebel, J. A., Piccirillo, J. F., Neely, J. G., & Black, O. (2003). Vestibular dysfunction after cochlear implantation. Otology and Neurotology, 24, Henderson, S. E., & Sugden, D. A. (1992). Movement assessment battery for children: Manual. London: Psychological Corporation. Horn, D. L., Pisoni, D. B., & Miyamoto, R. T. (2006). Divergence of fine and gross motor skills in prelingually deaf children: Implications for cochlear implantation. Laryngoscope, 116, Horn, D. L., Pisoni, D. B., Sanders, M., & Miyamoto, R. T. (2005). Behavioral assessment of prelingually deaf children before cochlear implantation. Laryngoscope, 115, Incesulu, A., Vural, M., & Erkam, U. (2003). Children with cochlear implants: Parental perspective. Otology and Neurotology, 24, Ito, J. (1998). Influence of the multichannel cochlear implant on vestibular function. Otolaryngology and Head and Neck Surgery, 118, Jin, Y., Nakamura, M., Shinjo, Y., & Kaga, K. (2006). Vestibularevoked myogenic potentials in cochlear implant children. Acta Otolaryngologica, 126, Kiphard, E. J., & Schilling, F. (1974). Körperkoordinationstest für Kinder. Weinheim, Germany: Beltz Test GmbH. Kubo, T., Yamamoto, K., Iwaki, T., Doi, K., & Tamura, M. (2001). Different forms of dizziness occurring after cochlear implant. European Archives of Otorhinolaryngology, 258, Kutz, W., Wright, C., Krull, K., & Manolidis, S. (2003). Neuropsychological testing in the screening for cochlear implant candidacy. Laryngoscope, 113, Leemrijse, C., Meijer, O. G., Vermeer, A., Lambregts, B., & Adèr, H. J. (1999). Detecting individual change in children with mild to moderate motor impairment: The standard

10 224 Journal of Deaf Studies and Deaf Education 13:2 Spring 2008 error of measurement of the Movement ABC. Clinical Rehabilitation, 13, Liao, H. F., Mao, P. J., & Hwang, A. W. (2001). Test-retest reliability of balance tests in children with cerebral palsy. Developmental Medicine and Child Neurology, 43, Lieberman, L. J., Volding, L., & Winnick, J. P. (2004). Comparing motor development of deaf children of deaf parents and deaf children of hearing parents. American Annals of the Deaf, 149, Migliaccio, A. A., Della Santina, C. C., Carey, J. P., Niparko, J. K., & Minor, L. B. (2005). The vestibulo-ocular reflex response to head impulses rarely decreases after cochlear implantation. Otology and Neurotology, 26, Miyamoto, R. T., Houston, D. M., Kirk, K. I., Perdew, A. E., & Svirsky, M. A. (2003). Language development in deaf infants following cochlear implantation. Acta Otolaryngologica, 123, Niparko, J. K. (2000). Cochlear implants: Principles and practices. Philadelphia: Lippincott Williams and Wilkins. Niparko, J. K., & Blankenhorn, R. (2003). Cochlear implants in young children. MRDD Research Reviews, 9, O Neill, D. E., Gill-Body, K. M., & Krebs, D. E. (1998). Posturography changes do not predict functional performance changes. The American Journal of Otology, 19, Robbins, A. M., Svirsky, M., & Kirk, K. I. (1997). Children with implants can speak, but can they communicate? Otolaryngology and Head and Neck Surgery, 117, Savelsbergh, G. J. P., Netelenbos, J. B., & Whiting, H. T. A. (1991). Auditory perception and the control of spatially coordinated action of deaf and hearing impaired children. Journal of Child Psychology and Psychiatry, 32, Schlumberger, E., Narbona, J., & Manrique, M. (2004). Nonverbal development of children with deafness with and without cochlear implants. Developmental Medicine and Child Neurology, 46, Siegel, J. C., Marchetti, M., & Tecklin, J. S. (1991). Age-related balance changes in hearing-impaired children. Physical Therapy, 71, Smits-Engelsman, B. C. (1998). Movement Assessment Battery for children: Handleiding. Lisse, The Netherlands: Swets. Smits-Engelsman, B. C. M., Henderson, S. E., & Michels, C. G. J. (1998). The assessment of children with developmental coordination disorders in the Netherlands: The relationship between the Movement Assessment Battery for Children and the Körperkoordinations Test für Kinder. Human Movement Science, 17, Steenerson, R. L., Cronin, G. W., & Gary, L. B. (2001). Vertigo after cochlear implantation. Otology and Neurotology, 22, Stevens, J. (1996). Applied multivariate statistics for the social sciences. Mahwah, NJ: Lawrence Erlbaum Associates. Suarez, H., Angeli, S., Suarez, A., Rosales, B., Carrera, X., & Alonso, R. (2007). Balance sensory organization in children with profound hearing loss and cochlear implants. International Journal of Pediatric Otorhinolaryngology, 71, Svirsky, M. A., Robbins, A. M., Kirk, K. I., Pisoni, D. B., & Miyamoto, R. T. (2000). Language development in profoundly deaf children with cochlear implants. Psychological Science, 11, Tien, H. C., & Linthicum, F. H. (2002). Histopathologic changes in the vestibule after cochlear implantation. Otolaryngology and Head and Neck Surgery, 127, Wiegersma, P. H., & Van der Velde, A. (1983). Motor development of deaf children. Journal of Child Psychology and Psychiatry, 24, Received March 18, 2007; revisions received September 23, 2007; accepted September 26, 2007.