Handwriting Deficits and Tourette’s Syndrome (TS): Is There a Connection?

Studies have reported high prevalence of children with Tourette syndrome (TS) having difficulties in academic performance.^1-3 The exact mechanism contributing to poor academic performance is not known. However, difficulty with writing, homework, and completing exams are among the major contributors that affect academic performance of children with TS.^1,3 Although circumstantial evidence suggests children with TS experience challenges in handwriting which may be attributed to their tics, few studies systematically investigated handwriting performance among children with TS. The purpose of this study was therefore to examine the link between TS and handwriting in children. It was hypothesized that the median percentile rank achieved by children with TS in a standardized handwriting skills assessment is significantly lower than that (i.e., median = 50) of the general children population.

This study employed a causal comparative research design. A convenience sample of children with TS were recruited from two clinical sites to participate in the handwriting assessment. Participants eligible for the study were school children 7 to 19 years of age, with a diagnosis of TS with or without co-morbidities, except excluding children with autism spectrum disorder, learning disability or dysgraphia.

Handwriting performance among children with TS was assessed using the Test of Handwriting Skills-Revised (THS-R),⁴ a norm-referenced standardized assessment. The THS-R also measures speed of writing, errors in letter reversal, touching letters or numbers, and case errors. The trained occupational therapists followed the guidelines in the THS-R manual to administer and score the writing samples. All writing samples were subjected to inter-rater agreement checks. The intra-class correlation coefficient (ICC [2,1]) between the occupational therapists’ overall percentile rank scores and the independent raters’ scores was .80 and the ICC score was comparable to the value reported in the THS-R manual.⁴

Since no significant differences in participants’ THS-R scores, age, school grade level, gender, and handedness between the two study sites were observed, the data from the two sites were combined for analysis. The primary outcome measure used in this study was the overall percentile rank. As percentile rank is an ordinal measure, a non-parametric statistical method was used to analyze the data.

Thirty-four children with TS completed the THS-R. A one-sample Wilcoxon signed-rank test revealed the median percentile ranks of the THS-R for participants (median = 24) were significantly lower than the median percentile score (median = 50) of the general children population. Close to 80% (n=27) of writing samples were scored below 50^th percentile. More than one-third (35.3%, n=12) of the writing samples were scored below 16^th percentile (one standard deviation, SD, or z-score of 1). Furthermore, more than 60% (n=21) of the participants’ writing samples scored one SD below the normative mean in either writing speed or case errors, with 29.4% (n=10) scored one SD below the normative mean in both case errors and writing speed.

The results of this study supported the hypothesis that children with TS demonstrated handwriting deficits when compared to the general children population. In addition to illegibility issues in handwriting as indicated by the low score on the THS-R, children with TS also demonstrated writing deficits in the areas of speed of writing and correct letter case formation. With the evidence provided in this study, practitioners should assess for handwriting limitations with this population, with particular focus on letter formation, legibility and writing speed.

References

1. Claussen, A. H., Bitsko, R. H., Holbrook, J. R., Bloomfield, J., & Giordano, K. (2018). Impact of Tourette Syndrome on School Measures in a Nationally Representative Sample. J Dev Behav Pediatr, 39(4), 335-342. doi:10.1097/dbp.0000000000000550

2. Conelea, C. A., Woods, D. W., Zinner, S. H., Budman, C., Murphy, T., Scahill, L. D., . . . Walkup, J. (2011). Exploring the impact of chronic tic disorders on youth: results from the Tourette Syndrome Impact Survey. Child Psychiatry Hum Dev, 42(2), 219-242. doi:10.1007/s10578-010-0211-4

3. Wadman, R., Glazebrook, C., Beer, C., & Jackson, G. M. (2016). Difficulties experienced by young people with Tourette syndrome in secondary school: a mixed methods description of self, parent and staff perspectives. BMC Psychiatry, 16, 14. doi:10.1186/s12888-016-0717-9

4. Milone, M. (2007). Test of Handwriting Skills-Revised. Novato, CA: Academic Therapy Publications.