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1 This article was downloaded by: [KU Leuven Biomedical Library] On: 27 January 2010 Access details: Access Details: [subscription number ] Publisher Psychology Press Informa Ltd Registered in England and Wales Registered Number: Registered office: Mortimer House, Mortimer Street, London W1T 3JH, UK Child Neuropsychology Publication details, including instructions for authors and subscription information: The Motor Profile of Primary School-Age Children with a 22q11.2 Deletion Syndrome (22q11.2DS) and an Age- and IQ-Matched Control Group Katrijn Van Aken a ; Karen Caeyenberghs b ; Bouwien Smits-Engelsman bc ; Ann Swillen ade a Department of Rehabilitation Sciences, Katholic University Leuven, Leuven, Belgium b Department of Biomedical Kinesiology, Katholic University Leuven, Leuven, Belgium c Avans+ University for Professionals, Breda, The Netherlands d University Hospital Gasthuisberg, Leuven, Belgium e Department of Human Genetics, Katholic University Leuven, Leuven, Belgium First published on: 11 March 2009 To cite this Article Van Aken, Katrijn, Caeyenberghs, Karen, Smits-Engelsman, Bouwien and Swillen, Ann(2009) 'The Motor Profile of Primary School-Age Children with a 22q11.2 Deletion Syndrome (22q11.2DS) and an Age- and IQ- Matched Control Group', Child Neuropsychology, 15: 6, , First published on: 11 March 2009 (ifirst) To link to this Article: DOI: / URL: PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

2 Child Neuropsychology, 15: , ISSN: print / online DOI: / THE MOTOR PROFILE OF PRIMARY SCHOOL-AGE CHILDREN WITH A 22Q11.2 DELETION SYNDROME (22Q11.2DS) AND AN AGE- AND IQ-MATCHED CONTROL GROUP Katrijn Van Aken, 1 Karen Caeyenberghs, 2 Bouwien Smits-Engelsman, 2,3 and Ann Swillen 1,4,5 1 Katholic University Leuven, Department of Rehabilitation Sciences, Leuven, Belgium, 2 Katholic University Leuven, Department of Biomedical Kinesiology, Leuven, Belgium, 3 Avans+ University for Professionals, Breda, The Netherlands, 4 University Hospital Gasthuisberg, Leuven, Belgium, and 5 Katholic University Leuven, Department of Human Genetics, Leuven, Belgium In the early publications on the 22q11.2 Deletion Syndrome (22q11.2DS) motor abnormalities have been frequently reported. However, systematic studies on the motor performance of children with the 22q11.2DS, and especially of school-age children, are scarce. In this study the motor performance of primary school-age children with a 22q11.2DS (n = 28) was compared with an age- and IQ-matched control group (n = 28) using the Movement Assessment Battery for Children (MABC), the Körperkoordinationstest für Kinder (KTK) and the Beery-Buctenica test of Visual-Motor Integration (Beery). Children with a 22q11.2DS scored significantly lower than the age- and IQ-matched control group on the subsection Manual Dexterity (MABC) and the Visual Perception and Motor Coordination subtests of the Beery. When investigating the correlations between Intelligence quotient (IQ) and motor performance, a specific profile was found in the 22q11.2DS group when compared with the age- and IQ-matched control group. Because an IQ-matched control group was adopted, the deficits in visual-perceptual and visuomotor integration skills cannot fully be attributed to a general developmental delay and thus may be specific for the 22q11.2DS. Future studies that investigate the specificity of the visual-perceptual problems both on the behavioral and brain level (functional Magnetic Resonance Imaging [fmri] and Diffusion Tensor Imaging [DTI]) are necessary to answer this question. Nonetheless, the importance of incorporating motor functioning into the study of the neuropsychological profile of children with a 22q11.2DS has to be stressed. Keywords: 22q11.2 deletion syndrome; Motor impairment; Intelligence; Children motor test; Motor development. Address correspondence to Katrijn Van Aken, Katholic University Leuven, Department of Rehabilitation Sciences, Tervuursevest 101, 3001 Leuven (Heverlee), Leuven, 3001 Belgium katrijn.vanaken@ faber.kuleuven.be 2009 Psychology Press, an imprint of the Taylor & Francis Group, an Informa business

3 THE MOTOR PROFILE OF CHILDREN WITH A 22Q11.2DS 533 INTRODUCTION The 22q11.2 Deletion Syndrome (22q11.2DS), which includes DiGeorge and velocardiofacial syndrome, is caused by a heterozygous deletion of approximately 3 megabases (Mb) of chromosome 22q11.2. This is the most common chromosomal deletion syndrome in man, with an incidence of approximately 1:4000 live births (Devriendt, Fryns, Mortier, van Thienen, & Keymolen, 1998). Most cases are de novo but the deletion can also be inherited from an affected parent. The clinical manifestations of the 22q11.2DS are highly variable but typically include a congenital heart defect (CHD), velopharyngeal insufficiency with or without cleft palate, mild to moderate immune deficiency, characteristic facial features, and learning disabilities (Kobrynski & Sullivan, 2007; Shprintzen, 2000; Swillen, Vogels, Devriendt, & Fryns, 2000). Often the 22q11.2DS diagnosis is made based on the cardiac anomalies of the child. However, 25% of the patients with 22q11.2DS do not have a CHD. Frequently, these children are diagnosed with a delay of several years. Therefore it is important that clinicians have knowledge of the different clinical manifestations of the 22q11.2DS to make an early diagnosis possible (Kobrinsky & Sullivan). Additionally, subjects with a 22q11.2DS show a higher risk for the development of psychiatric problems during adolescence and early adulthood (Shprintzen; Swillen et al., 2000). Impaired cognitive development is present in 70% to 80% of patients, though severe learning disability is rare (De Smedt et al., 2007; Swillen et al., 1997). Also motor abnormalities, such as hypotonia and delayed motor development, are frequently reported in the early publications on the 22q11.2DS (Gerdes et al., 1999; Shprintzen et al., 1978); however, systematic studies on the motor performance of children with the 22q11.2DS, and especially of school-age children, are scarce (Oskarsdottir, Belfrage, Sandstedt, Viggedal, & Uvebrant, 2005; Sobin et al., 2006; Swillen et al., 2005; Van Aken et al., 2007). In these studies, deficits in motor functioning in 22q11.2DS have been documented by using standardized testing procedures. Sobin, Monk, Kiley-Brabeck, Khuri, and Karayiorgou (2006), for example, found significant differences between the children with 22q11.2DS and their siblings, using the Movement Assessment Battery for Children (MABC; Henderson & Sugden, 1992), both on gross motor subtests (balance) and on fine motor items (manual dexterity, eye-hand coordination). Others have also found deficits in balance using the Bruininks Oseretsky test of Motor Proficiency (BOTMP; Bruininks, 1978; Van Aken et al.). However, earlier research was mostly explorative; no IQ-matched controls were used to evaluate the motor performance of the children with the 22q11.2DS. Since children with a 22q11.2DS show a delayed development with an average Full Scale Intelligence Quotient (FSIQ) of 70 (Swillen et al., 1997), age- and IQ-matched control groups have to be adopted to sort out whether the motor problems in 22q11.2DS are specific for this group or are (partially) due to a general developmental delay. Therefore, in this study the motor performance of primary school-aged children with a 22q11.2DS were compared with age- and IQ-matched controls (1/1-subject matched). Secondly, the relation between IQ and motor performance in the 22q11.2DS group was investigated by calculating Spearman correlations. METHODS Participants Fifty-six children participated in the study, including 28 children with a 22q11.2DS (mean age = 9.65 years, SD = 1.93; 10 girls and 18 boys; mean IQ = 73.89, SD = 15.16) and 28 control children (mean age = 9.56 years, SD = 1.68; 8 girls and 20 boys; mean

4 534 K. VAN AKEN ET AL. IQ = 73.29, SD = 14.08). The children with a 22q11.2DS were recruited from the multidisciplinary 22q11.2DS-clinic at the Center for Human Genetics (University Hospital Gasthuisberg) in Leuven. Parents and children visit the clinic on a regular basis and are followed up by a multidisciplinary team. Detailed medical data are available, as well as family history, age at diagnosis, mode of inheritance (de novo versus familial deletion), and IQ. Premature children (gestation <36 weeks) and children with epilepsy were excluded. This group will be referred to as the 22q11.2DS group. The control group was matched to the children with 22q11.2DS on the basis of age and FSIQ. Therefore these children were recruited from three special education schools in the region of Leuven. Exclusion criteria were a diagnosed genetic disorder, epilepsy, prematurity (gestation <36 weeks), or a FSIQ below 50. The control group consisted of 11 children with a learning disability (LD), 11 children with a mild intellectual disability (MID), and 6 children with a moderate intellectual disability (MOID). For the MABC, analyses were performed on all 56 subjects. Analyses on the data of the Körperkoordinationstest für Kinder (KTK) were performed on 14 subjects with a 22q11.2DS (mean age = 9.81 years, SD = 1.88; mean IQ = 65.29, SD = 11.32) and 14 controls (mean age = 9.56 years, SD = 1.66; mean IQ = 65.21, SD = 10.80) because for the 22q11.2DS children with a higher IQ (FSIQ >70) no suitable control subjects were available (due to missing KTK data in the LD group). For the analyses of the Beery, 26 children with a 22q11.2DS (mean age = 9.78, SD = 1.89; mean IQ = 74.96, SD = 14.34) and 26 control children (mean age = 9.97, SD = 1.57; mean IQ = 74.04, SD = 13.10) were adopted because of missing data of 2 children of the 22q11.2DS group. For the subtest Visual Perception, data of 25 subjects with 22q11.2DS and 25 controls were available. Movement Assessment Battery for Children (MABC) General motor performance was assessed using the Movement Assessment Battery for Children (MABC; Henderson & Sugden, 1992 ). The MABC is a norm-ranked assessment used to investigate the presence of a developmental motor disorder in school-aged children (4 12 years). The MABC provides quantitative data about a child s performance of age-appropriate tasks with three subsections: manual dexterity (three items), ball skills (two items), and static and dynamic balance (three items). There are two sorts of tasks at each item level: time-related (scored in seconds) and error-related (scored by number of good attempts). The eight items are different for each age band but cover similar skills. The raw performance score of each item is converted into a scaled score ranging from 0 to 5, with lower scores indicating a better performance (manual dexterity: maximum [worst] score of 15; ball skills: maximum [worst] score of 10; static and dynamic balance: maximum [worst] score of 15). A range of percentile scores is matched to these scaled scores. The total impairment score of the test is the sum of scaled scores (with a maximum total score of 40). The higher the total score on the MABC, the worse the motor performance. The manual provides a table for converting the total impairment score into a percentile score. In 1998, Smits-Engelsman translated the MABC into Dutch and validated the instrument for the Dutch population. Because this study is conducted in the Dutch-speaking part of Belgium, the Dutch version of the MABC was used. Körperkoordinationstest für Kinder (KTK) The KTK (Kiphard & Schilling, 1974 ) is used to measure dynamic coordination and body control of children between 5 and 14 years. The KTK consist of four test

5 THE MOTOR PROFILE OF CHILDREN WITH A 22Q11.2DS 535 items: (a) walking backwards on a balance beam (3 cm, 4.5 cm, 6 cm), (b) hopping over an obstacle, (c) jumping sideways over a wooden board, and (d) moving sideways using two wooden boxes. The raw scores of the four test items are each converted in a motor quotient (MQ). The four MQs are summed and transformed into a Total MQ (mean = 100, SD = 15). The manual provides a table for converting the Total MQ score into a percentile score. The higher the score on the KTK, the better the motor performance. Beery-Buktenica Developmental Test of Visual-Motor Integration (Beery) The Visual-Motor Integration test (VMI) and its two supplemental tests, Visual Perception (VIS) and Motor Coordination (MOT), provide the most valid visual-motor screening battery available for children and adolescents (Beery, 1997). The VMI is designed to assess the extent to which individuals can integrate their visual and motor abilities. The VMI is a developmental sequence of geometric forms to be copied with paper and pencil. The full 27-item VMI can be either group or individually administered in about 10 to 15 minutes. In the standardized Visual Perception test (VIS), one geometric form that is exactly the same as each stimulus figure is to be chosen from other figures that are not exactly the same as the stimulus figure. During a 3-minute period, the task is to identify the exact match for as many of the 27 figures as possible. In the Motor Coordination test (MOT), the task is to trace the figure forms with a pencil without going outside double-lined paths. The Motor Coordination task takes about 5 minutes to administer. Raw scores of the three tests are converted into standard scores (mean = 100, SD = 15) and subsequently into percentile scores. The higher the score on the Beery, the better the motor performance. IQ The most recent IQ data of all children were collected from their medical files (school/parents). The following tests were used to collect the IQ scores: Snijder-Oomen Nonverbal intelligence test (SON-R; Snijders & Snijders-Oomen, 1975), Wechsler Intelligence Scale for Children - III (WISC-III; Wechsler, 1999), Wechsler Preschool and Primary Scale of Intelligence- Revised (WPPSI-R; Wechsler, 1992), Leidse Diagnostische Test (LDT; Schroots & Alphen de Veer, 1976), McCarthy Scales of Children s Abilities (MOS; McCarthy, 1972), and Revised Amsterdam Child Intelligence Test (RAKIT; Bleichrodt, Drenth, Zaal, & Resing, 1984). Procedure Data were collected between March 2006 and December 2007 by experienced examiners. Families were addressed by letter or by phone. The children with a 22q11.2DS were tested individually at home or at the child s school in a quiet environment (MABC + KTK + Beery). The children of the control group were tested at the child s school. The MABC and the KTK were administered individually in a quiet environment; the Beery was performed in group (class) except for the children with MOID where the Beery was also administered individually. All tests were administered and scored according to the standardized procedures. Written informed consent was obtained from all participating families. The study protocol was approved by the Ethical Committee of the University Hospital Gasthuisberg.

6 536 K. VAN AKEN ET AL. Analyses All analyses were done using the SAS computer program (SAS version 9.1). The scaled scores of the MABC and the Beery and the MQ scores of the KTK were used in the analyses. Descriptive statistics of all groups were calculated. First, the motor performance of the 22q11.2DS group on the MABC, KTK, and the Beery was compared with an ageand IQ-matched control group (subject-matched) using a Wilcoxon signed-rank test. Next, Spearman correlations were calculated to investigate the relation between IQ and motor performance. Level of significance was set at p <.05. RESULTS First, the motor performance on the MABC, the KTK, and the Beery of primary school-aged children with a 22q11.2DS and an age- and IQ-matched control group were compared. The 22q11.2DS group scored significantly higher than the control group for the subtest Manual Dexterity (MABC; p =.038), meaning that the 22q11.2DS group performed significantly worse than the control group on the manual dexterity tasks of the MABC. Next, significant differences were found between the 22q11.2DS and the control group for the subtests VIS (p =.008) and MOT (p <.001) of the Beery. The 22q11.2DS achieved lower scores for these tests than the controls and thus again the 22q11.2DS performed worse than the control group. On the KTK no significant differences between the two groups were found (Table 1). Second, the relation between IQ (FSIQ, Verbal Intelligence Quotient [VIQ], and Performance Intelligence Quotient [PIQ]) and motor performance was investigated by calculating Spearman correlations. In the 22q11.2DS group high scores on the total Table 1 Comparison of the Motor Performance (MABC, KTK, Beery) of a 22q11.2DS Group and an Age- And IQ-Matched Control Group (Wilcoxon signed-rank test). n 22q11.2DS group Mean ± SD n Control group Mean ± SD MABC Manual dexterity ± ± * Ball skills ± ± Balance skills ± ± Total score MABC ± ± KTK MQ ± ± MQ ± ± MQ ± ± MQ ± ± Total MQ ± ± LD Total MQ ± ± Beery VMI ± ± VIS ± ± ** MOT ± ± <.001** p *p <.05. **p <.01. LD = learning disabled; MQ = motor quotient; VMI = visual motor integration subtest; VIS = visual perception subtest; MOT = motor coordination subtest.

7 THE MOTOR PROFILE OF CHILDREN WITH A 22Q11.2DS Total MABC FSIQ 22q11.2DS Linear (22q11.2DS) r = r = age- and IQ matched controls Linear (age- and IQ matched controls) Figure 1 Spearman correlations between FSIQ and total score MABC: 22q11.2DS versus age- and IQ-matched control group. Scatterplot of the total score MABC-FSIQ of the 22q11.2DS group and the control group. Spearman correlation coefficients between total score MABC and FSIQ of the 22q11.2DS group (r =.50) and the age- and IQ-matched control group (r =.57) are shown. score MABC and the Ball Skill subscore (MABC) coincided with low FSIQ, r =.50 and r =.41, respectively (Figure 1). VIQ was negatively correlated with the Manual Dexterity subscore (MABC; r =.47) and the total score MABC (r =.59). Moreover, high scores on Ball skills (r =.39) and on the total score MABC (r =.59) correlated with low PIQ. Since the MABC high scores resemble bad performance, negative correlations between IQ and the MABC were found. Lower scores on the VIS subtest (Beery) were associated with lower FSIQ (r =.40). Finally, VMI (r =.46) and MOT (r =.50) were positively correlated with PIQ. No significant correlations were found between IQ (FSIQ, VIQ, PIQ) and the KTK (Table 2). In the control group the total MABC score (r =.57) as well as the Manual Dexterity subscore (MABC; r =.61), the Ball Skill subscore (MABC; r =.57) and the Balance subscore (MABC; r =.51) were negatively correlated with FSIQ. Poor scores on the VMI subtest (Beery; r =.49) and the MOT subtest (Beery; r =.51) coincided with low IQ. Between PIQ and Manual Dexterity (MABC; r =.43), between PIQ and total score MABC (r =.43), and between PIQ and the VIS subtest (Beery: r =.46), significant correlations were found. No significant correlations were found between VIQ and motor performance nor between IQ (FSIQ, VIQ, PIQ) and the KTK (Table 2). DISCUSSION The aim of this study was to compare the motor performance of primary school-age children with a 22q11.2DS and age- and IQ-matched controls, using the MABC, the KTK, and the Beery. A 1/1-subject matching was performed (based on FSIQ and age) and the motor performance of the 22q11.2DS group and the age- and IQ-matched control group

8 538 K. VAN AKEN ET AL. Table 2 Spearman Correlations Between IQ (FSIQ, VIQ, PIQ) and Motor Performance. 22q11.2DS Group Control Group FSIQ VIQ PIQ FSIQ VIQ PIQ MABC n Manual dexterity.36.47*.33.61** Ball skills.41*.38.39*.57**.05.43* Balance skills ** Total score MABC.50**.59**.59**.57**.10.43* KTK n MQ MQ MQ MQ Total MQ LD total MQ Beery n VMI *.49* VIS.40* * MOT *.51** *p <.05. **p <.01. FSIQ = Full Scale Intelligence Quotient; VIQ= Verbal Intelligence Quotient; PIQ= Performal Intelligence Quotient; MQ = motor quotient; LD = learning disabled; VMI = visual motor integration subtest; VIS = visual perception subtest; MOT = motor coordination subtest. was compared. Children with a 22q11.2DS scored significantly worse than the controls on the subsection Manual Dexterity of the MABC and the subtests VIS and MOT of the Beery. These data suggest that the visual-perceptual and visuomotor integration skills are specifically affected in children with a 22q11.2DS compared to age- and IQ-matched controls. These findings are similar to the findings by Sobin and colleagues (2005), who reported lowered scores in visual attention, working memory, and motor function (fine motor dexterity, kinesthetic awareness and visual-motor precision) in primary school-aged children with 22q11.2DS compared to age-matched controls. In our study the children with 22q11.2DS were matched for FSIQ, therefore the deficits in visual-perceptual and visuomotor integration cannot be attributed to a general developmental delay and may be specific for the 22q11.2DS. Because of the frequently reported problems in visuomotor integration in children with 22q11.2DS, different aspects of visual perceptual and visuomotor integration skills in subjects with 22q11.2DS have been recently investigated. Bearden and colleagues (2001) found a selective deficit in visual-spatial memory in 22q11.2DS, which was mirrored by deficits in arithmetic and general visual-spatial recognition. When investigating the temporal reproduction and perception skills in subjects with 22q11.2DS, it was found that subjects with 22q11.2DS are less accurate and show a greater variability in reproducing a fixed tapping cadence than typically developing controls (age range = 6 39 years; Debbane, Glaser, Gex-Fabry, & Eliez, 2005). Simon, Bearden, Mc-Ginn, and Zackai

9 THE MOTOR PROFILE OF CHILDREN WITH A 22Q11.2DS 539 (2005) reported that a 22q11.2DS group performed more poorly on tests of visual orienting, visual enumeration, and relative numerical magnitude judgement than a control group of siblings and typically developing children (age range = 7 15 years). Bish, Chiodo, Mattei, & Simon (2007) confirmed the problems in visuomotor integration skills in children with 22q11.2DS. Surprisingly, children with a 22q11.2DS showed significant facilitation in performance when using object-based attention. Rather than being equally impaired in using attentional visuospatial processes, they appear to have a relative strength in using object boundaries to structure visual space (Bish et al.). Studies that investigate visual perception skills in a 22q11.2DS population are scarce (Andersson et al., 2008; Lajiness-O Neill et al., 2005; van Amelsvoort et al., 2006). In these recent studies marked impairments in face and emotional processing (especially face memory) in 22q11.2DS were found. Also in the present study the problems in visualperception and visuomotor integration skills in children with 22q11.2DS were confirmed. The reported problems cannot solely be attributed to a general developmental delay because an age- and IQ-matched control group was used and hereby the effect of FSIQ on the motor performance was corrected for. There are several possible explanations for the visual-perceptual and visuomotor integration problems seen in children with a 22q11.2DS. One is that these problems could be influenced by a visual disorder. Two sorts of visual disorders exist namely the ocular visual impairment (OVI), which is caused by pathology of the eye, and the neurological visual disorder (cerebral visual impairment [CVI]), which is caused by various brain abnormalities. OVIs can be traced by performing an (standard) ophthalmological examination. In subjects with 22q11.2DS there is a high incidence of ophthalmological abnormalities and often refractive correction in those subjects is needed (Casteels et al., 2007; Forbes et al., 2007). In the present study no systematic ophthalmological examination was performed in the 22q11.2DS subjects and thus part of the problems seen in our study population may be caused by an uncorrected OVI. Therefore, in the future it is recommended to incorporate a systematic ophthalmological screening of all children with 22q11.2DS when studying their neuropsychological profile. The presence of a CVI in some children with an OVI could also be possible. In the visual-information processing system of the human brain two broad streams of projections from the primary visual cortex can be distinguished: a ventral stream (from visual cortex to occipital and temporal brain areas: what stream), concerned with the appearance of individual objects, and the dorsal stream (from visual cortex to occipital and parietal brain areas: where stream), concerned with the location and movement of objects in space (Bearden et al., 2001; Mishkin & Ungerleider, 1982). To our knowledge, there are no systematic studies on the incidence/prevalence of CVI in the 22q11.2DS population (except for a case study by Stiers et al. (2005) but the visual-perceptual and visuomotor problems seen in the 22q11.2DS population suggest a dysfunction of both the occipital-temporal pathway (ventral stream; Andersson et al., 2008; Lajiness-O Neill et al., 2005; van Amelsvoort et al., 2006) and the occipital-parietal stream (dorsal stream; Bearden et al., 2001; Bish et al., 2007; Simon et al., 2005), possibly due to dysmaturation of white-matter tracts in this syndrome (Lajiness-O Neill et al.; van Amelsvoort et al.). The abnormal connectivity in the brain may influence different areas of development (motor functioning, social functioning, etc.) and can be an explanation for the wide variability of impairments seen in 22q11.2DS. However, this suggestion is pure hypothetical because the tests used in the present study are not sufficiently specific to determine whether the impairments seen in the 22q11.2DS are due to differential impairment of a particular pathway. Future studies

10 540 K. VAN AKEN ET AL. that investigate the specificity of the visual-perceptual problems both on the behavioral and brain level (fmri and DTI) are necessary to answer this question. Secondly, the typical impaired nonverbal profile in children with 22q11.2DS could be another explanation for the findings. Children with 22q11.2DS show higher VIQ than PIQ scores (Bearden et al., 2001; Moss et al., 1999; Swillen et al., 1999; Wang, Woodin, Kreps-Falk, & Moss, 2000). The weaker nonverbal abilities and impairments in visuomotor skills in the 22q11.2DS group can partly be explained by the deficits in visuospatial memory capacity in the 22q11.2DS (Bearden et al.). Because the children of the 22q11.2DS and the controls were matched on FSIQ, the typical nonverbal profile (VIQ> PIQ) of the 22q11.2DS may be responsible for the differences in correlations between IQ and motor functioning in the 22q11.2DS group and the controls (Table 2). A possible explanation for the higher correlations between VIQ and motor performance in the 22q11.2DS is that children with a 22q11.2DS develop and use verbal compensation strategies, because of their relatively stronger verbal capacities, to talk themselves through motor tasks and ameliorate their performance on certain motor tasks. However, this will need to be an area of further investigation in future studies. Strengths and Limitations Strengths. The use of age- and IQ-matched controls and the 1/1-subject matching are important strengths of this study. Since children with a 22q11.2DS have an average FSIQ of 70 the use of appropriate controls (age- and IQ-matched, no specific genetic disorder) is crucial. Limitations. First, in this study only global aspects of motor performance in 22q11.2DS were studied. More studies that investigate different aspects of motor functioning and specific neuromotor processes in more detail are necessary. Secondly, three standardized motor batteries (MABC, KTK, Beery) were used to investigate the general motor performance in children with 22q11.2DS. The use of more appropriate tests, adapted to the population of children with an intellectual disability (ID), would be advisable. Because no such tests are available we tried to correct for possible measurement errors by using an IQ-matched control group. Third, there is a slight difference between the 22q11.2DS group and the control group regarding boy-girl ratio. However, no significant differences in motor performance (MABC, KTK, Beery) were found between boys and girls within the two groups. Therefore it is assumed that boy-girl ratio did not influence the results of this study. CONCLUSION Primary school-age children with a 22q11.2DS show impairments in visual-perception and visuomotor integration skills when compared with age- and IQ-matched controls. These problems cannot be (fully) attributed to a general developmental delay but seem to be specific for the 22q11.2DS. Future studies that investigate the specificity of the visual-perceptual and visuomotor problems both on the behavioral and brain level (imaging) are necessary to answer this question. However, the importance of incorporating motor functioning into the study and interpretation of the neuropsychological profile of children with a 22q11.2DS has to be stressed. To rule out possible

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