Publications by authors named "Tjitske F Lawerman"

8 Publications

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Paediatric motor phenotypes in early-onset ataxia, developmental coordination disorder, and central hypotonia.

Dev Med Child Neurol 2020 01 17;62(1):75-82. Epub 2019 Sep 17.

Department of Pediatrics, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.

Aims: To investigate the accuracy of phenotypic early-onset ataxia (EOA) recognition among developmental conditions, including developmental coordination disorder (DCD) and hypotonia of central nervous system origin, and the effect of scientifically validated EOA features on changing phenotypic consensus.

Method: We included 32 children (4-17y) diagnosed with EOA (n=11), DCD (n=10), and central hypotonia (n=11). Three paediatric neurologists independently assessed videotaped motor behaviour phenotypically and quantitatively (using the Scale for Assessment and Rating of Ataxia [SARA]). We determined: (1) phenotypic interobserver agreement and phenotypic homogeneity (percentage of phenotypes with full consensus by all three observers according to the underlying diagnosis); (2) SARA (sub)score profiles; and (3) the effect of three scientifically validated EOA features on phenotypic consensus.

Results: Phenotypic homogeneity occurred in 8 out of 11, 2 out of 10, and 1 out of 11 patients with EOA, DCD, and central hypotonia respectively. Homogeneous phenotypic discrimination of EOA from DCD and central hypotonia occurred in 16 out of 21 and 22 out of 22 patients respectively. Inhomogeneously discriminated EOA and DCD phenotypes (5 out of 21) revealed overlapping SARA scores with different SARA subscore profiles. After phenotypic reassessment with scientifically validated EOA features, phenotypic homogeneity changed from 16 to 18 patients.

Interpretation: In contrast to complete distinction between EOA and central hypotonia, the paediatric motor phenotype did not reliably distinguish between EOA and DCD. Reassessment with scientifically validated EOA features could contribute to a higher phenotypic consensus. Early-onset ataxia (EOA) and central hypotonia motor phenotypes were reliably distinguished. EOA and developmental coordination disorder (DCD) motor phenotypes were not reliably distinguished. The EOA and DCD phenotypes have different profiles of the Scale for Assessment and Rating of Ataxia.
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http://dx.doi.org/10.1111/dmcn.14355DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6916203PMC
January 2020

Construct Validity and Reliability of the SARA Gait and Posture Sub-scale in Early Onset Ataxia.

Front Hum Neurosci 2017 13;11:605. Epub 2017 Dec 13.

Departments of Pediatrics and Neurology, Beatrix Children's Hospital, University Medical Center Groningen, Groningen, Netherlands.

In children, gait and posture assessment provides a crucial marker for the early characterization, surveillance and treatment evaluation of early onset ataxia (EOA). For reliable data entry of studies targeting at gait and posture improvement, uniform quantitative biomarkers are necessary. Until now, the pediatric test construct of gait and posture scores of the Scale for Assessment and Rating of Ataxia sub-scale (SARA) is still unclear. In the present study, we aimed to validate the construct validity and reliability of the pediatric (SARA) sub-scale. We included 28 EOA patients [15.5 (6-34) years; median (range)]. For inter-observer reliability, we determined the ICC on EOA SARA sub-scores by three independent pediatric neurologists. For convergent validity, we associated SARA sub-scores with: (1) Ataxic gait Severity Measurement by Klockgether (ASMK; dynamic balance), (2) Pediatric Balance Scale (PBS; static balance), (3) Gross Motor Function Classification Scale -extended and revised version (GMFCS-E&R), (4) SARA-kinetic scores (SARA; kinetic function of the upper lower limbs), (5) Archimedes Spiral (AS; kinetic function of the upper limbs), and (6) total SARA scores (SARA; i.e., summed SARA, SARA, and SARA sub-scores). For discriminant validity, we investigated whether EOA co-morbidity factors (myopathy and myoclonus) could influence SARA sub-scores. The inter-observer agreement (ICC) on EOA SARA sub-scores was high (0.97). SARA was strongly correlated with the other ataxia and functional scales [ASMK ( = -0.819; < 0.001); PBS ( = -0.943; < 0.001); GMFCS-E&R ( = -0.862; < 0.001); SARA ( = 0.726; < 0.001); AS ( = 0.609; = 0.002); and SARA ( = 0.935; < 0.001)]. Comorbid myopathy influenced SARA scores by concurrent muscle weakness, whereas comorbid myoclonus predominantly influenced SARA scores. In young EOA patients, separate SARA parameters reveal a good inter-observer agreement and convergent validity, implicating the reliability of the scale. In perspective of incomplete discriminant validity, it is advisable to interpret SARA scores for comorbid muscle weakness.
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http://dx.doi.org/10.3389/fnhum.2017.00605DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5733344PMC
December 2017

Age-related reference values for the pediatric Scale for Assessment and Rating of Ataxia: a multicentre study.

Dev Med Child Neurol 2017 10 17;59(10):1077-1082. Epub 2017 Aug 17.

Department of Pediatrics, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.

Aim: For reliable assessment of ataxia severity in children, the Childhood Ataxia and Cerebellar Group of the European Pediatric Neurology Society aimed to validate the Scale for Assessment and Rating of Ataxia (SARA) according to age.

Method: Twenty-two pediatric ataxia experts from 15 international institutions scored videotaped SARA performances in 156 typically developing children (4-16y: m/f=1; 12 children per year of age; including nine different nationalities). We determined age-dependency and reliability of pediatric SARA scores by a mixed model.

Results: In typically developing children, age was the only variable that revealed a relationship with SARA scores (p<0.001). The youngest children revealed the highest scores and the highest variation in scores (<8y; p<0.001). After 11 years of age, pediatric scores approached adult outcomes. The interobserver agreement of total SARA scores was substantial with an intraclass correlation coefficient of 0.63 (95% confidence interval 0.56-0.69; p<0.001).

Interpretation: In typically developing European children, both SARA scores and interobserver agreement are age-dependent. For reliable interpretation of pediatric SARA scores, consideration of the underlying test construct appears prudent. These data will hopefully contribute to a correct and uniform interpretation of longitudinal SARA scores from childhood to adulthood.
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http://dx.doi.org/10.1111/dmcn.13507DOI Listing
October 2017

Automatic classification of gait in children with early-onset ataxia or developmental coordination disorder and controls using inertial sensors.

Gait Posture 2017 02 2;52:287-292. Epub 2016 Dec 2.

The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy.

Early-Onset Ataxia (EOA) and Developmental Coordination Disorder (DCD) are two conditions that affect coordination in children. Phenotypic identification of impaired coordination plays an important role in their diagnosis. Gait is one of the tests included in rating scales that can be used to assess motor coordination. A practical problem is that the resemblance between EOA and DCD symptoms can hamper their diagnosis. In this study we employed inertial sensors and a supervised classifier to obtain an automatic classification of the condition of participants. Data from shank and waist mounted inertial measurement units were used to extract features during gait in children diagnosed with EOA or DCD and age-matched controls. We defined a set of features from the recorded signals and we obtained the optimal features for classification using a backward sequential approach. We correctly classified 80.0%, 85.7%, and 70.0% of the control, DCD and EOA children, respectively. Overall, the automatic classifier correctly classified 78.4% of the participants, which is slightly better than the phenotypic assessment of gait by two pediatric neurologists (73.0%). These results demonstrate that automatic classification employing signals from inertial sensors obtained during gait maybe used as a support tool in the differential diagnosis of EOA and DCD. Furthermore, future extension of the classifier's test domains may help to further improve the diagnostic accuracy of pediatric coordination impairment. In this sense, this study may provide a first step towards incorporating a clinically objective and viable biomarker for identification of EOA and DCD.
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http://dx.doi.org/10.1016/j.gaitpost.2016.12.002DOI Listing
February 2017

Reliability and discriminant validity of ataxia rating scales in early onset ataxia.

Dev Med Child Neurol 2017 04 21;59(4):427-432. Epub 2016 Oct 21.

Department of Pediatrics, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.

Aim: To determine whether ataxia rating scales are reliable disease biomarkers for early onset ataxia (EOA).

Method: In 40 patients clinically identified with EOA (28 males, 12 females; mean age 15y 3mo [range 5-34y]), we determined interobserver and intraobserver agreement (interclass correlation coefficient [ICC]) and discriminant validity of ataxia rating scales (International Cooperative Ataxia Rating Scale [ICARS], Scale for Assessment and Rating of Ataxia [SARA], and Brief Ataxia Rating Scale [BARS]). Three paediatric neurologists independently scored ICARS, SARA and BARS performances recorded on video, and also phenotyped the primary and secondary movement disorder features. When ataxia was the primary movement disorder feature, we assigned patients to the subgroup 'EOA with core ataxia' (n=26). When ataxia concurred with other prevailing movement disorders (such as dystonia, myoclonus, and chorea), we assigned patients to the subgroup 'EOA with comorbid ataxia' (n=12).

Results: ICC values were similar in both EOA subgroups of 'core' and 'comorbid' ataxia (0.92-0.99; ICARS, SARA, and BARS). Independent of the phenotype, the severity of the prevailing movement disorder predicted the ataxia rating scale scores (β=0.83-0.88; p<0.05).

Interpretation: In patients with EOA, the reliability of ataxia rating scales is high. However, the discriminative validity for 'ataxia' is low. For adequate interpretation of ataxia rating scale scores, application in uniform movement disorder phenotypes is essential.
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http://dx.doi.org/10.1111/dmcn.13291DOI Listing
April 2017

Reliability of phenotypic early-onset ataxia assessment: a pilot study.

Dev Med Child Neurol 2016 Jan 21;58(1):70-6. Epub 2015 May 21.

Paediatrics, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.

Aim: To investigate the interobserver agreement on phenotypic early-onset ataxia (EOA) assessment and to explore whether the Scale for Assessment and Rating of Ataxia (SARA) could provide a supportive marker.

Method: Seven movement disorder specialists provided independent phenotypic assessments of potentially ataxic motor behaviour in 40 patients (mean age 15y [range 5-34]; data derived from University Medical Center Groningen medical records 1998-2012). We determined interobserver agreement by Fleiss' kappa. Furthermore, we compared percentage SARA subscores ([subscore/total score]×100%) between 'indisputable' (primary ataxia recognition by at least six observers) and 'mixed' (ataxia recognition, unfulfilling 'indisputable' criteria) EOA phenotypes.

Results: Agreement on phenotypic EOA assessment was statistically significant (p<0.001), but of moderate strength (Fleiss' kappa=0.45; 95% CI 0.38-0.51). During mild disease progression, percentage SARA gait subscores discriminated between 'indisputable' and 'mixed' EOA phenotypes. In patients with percentage SARA gait subscores >30%, primary ataxia was more frequently present than in those with subscores <30% (p=0.001).

Interpretation: Among movement-disorder professionals from different disciplines, interobserver agreement on phenotypic EOA recognition is of limited strength. SARA gait subscores can provide a supportive discriminative marker between EOA phenotypes. Hopefully, future phenotypic insight will contribute to the inclusion of uniform, high-quality data in international EOA databases.
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http://dx.doi.org/10.1111/dmcn.12804DOI Listing
January 2016

Assessment of speech in early-onset ataxia: a pilot study.

Dev Med Child Neurol 2014 Dec 18;56(12):1202-1206. Epub 2014 Jun 18.

Department of Paediatrics, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.

Aim: The aim of the study was to determine whether paediatric ataxia speech subscores are reliably applicable for international early-onset ataxia (EOA) databases. If so, we reasoned that ataxia speech subscores should be associated with ataxia scores and involve high interobserver agreement, including those for internationally applicable Scale for Assessment and Rating of Ataxia (SARA) syllable repetition tasks (SARASRT).

Method: Three independent paediatric neurologists and a speech therapist scored speech in 52 healthy children (mean age 10y, range 4-16y) and 40 individuals with EOA (mean age 15y, range 5-34y). We compared ataxia speech subscores for the association with age and ataxia scores as well as interobserver reliability.

Results: In healthy children, ataxia speech subscores were moderately associated with age (International Cooperative Ataxia Rating Scale [ICARS]: r=-0.515; SARA: r=-0.321; p<0.05) and with ataxia scores (ICARS: r=0.552; SARA: r=0.336; p<0.05), and revealed slight to moderate interobserver agreement (ICARS-intraclass correlation coefficient [ICC]: 0.380; SARA-ICC: 0.185; SARASRT-ICC: 0.509). In EOA, speech subscores have a strong association with ataxia scores (ICARS: r=0.735; SARA: r=0.730; p<0.001) and revealed substantial to nearly perfect interobserver agreement (ICARS-ICC: 0.812; SARA-ICC: 0.854; SARASRT-ICC: 0.724).

Interpretation: Early-onset ataxia speech subscores are associated with ataxia and also reveal high interobserver agreement, including those internationally applicable to SARASRT. We conclude that SARASRT appears to be applicable for EOA databases. However, before syllable repetition tasks are included, we would advise to wait for the results published by the international Childhood Ataxia and Cerebellar Group.
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http://dx.doi.org/10.1111/dmcn.12517DOI Listing
December 2014

Yet another role for SIRT1: reduction of α-synuclein aggregation in stressed neurons.

J Neurosci 2012 May;32(19):6413-4

Department of Neuroscience, University Medical Centre Groningen, Graduate School for Behavioral and Cognitive Neurosciences, University of Groningen, 9713 AV Groningen, The Netherlands.

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http://dx.doi.org/10.1523/JNEUROSCI.0959-12.2012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6621114PMC
May 2012
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