Rationale: Deficits in processing speed and attention are common in those with epilepsy and are frequently measured using the written Trail Making Test (TMT) and Symbol Digit Modalities Task (SDMT). Oral versions of these tasks are more easily used in a teleneuropsychology (TeleNP) context, increasingly employed now, though the equivalence of oral and written forms is little studied in clinical cohorts. This study aimed to evaluate this in individuals with seizure disorders.
Methods: This study included 91 participants (57.1% female, 41.8% male; M
age = 36.2, SD
age = 12.1, Age Range: 18.3 – 62.7) recruited to the Australian Epilepsy Project (
https://epilepsyproject.org.au/). Participants completed the oral TMT and SDMT during an AEP TeleNP assessment and the written TMT and SDMT in-person during a site visit.
Results: There was a strong positive relationship between the oral and written SDMT, r (84) = .82, p < .001. Both measures were highly correlated with other measures of processing speed and attention. The relationship between the oral and written TMT-B was relatively weaker, r (79) = .55, p < .001. The written TMT-B was more strongly related to measures of sustained attention and spatial working memory than its oral counterpart, reflecting the written task’s longer duration and visual search demands. The relationship between the oral and written TMT-B was also weaker than has been reported in samples of healthy controls (i.e., r = .62,
1 r = .72
2). Participants in our sample made a greater number of errors on the oral (M = 1.2, SD = 1.5) rather than the written TMT-B (M = 0.5, SD = 0.7), and also relative to normative samples (oral TMT-B
1: 0.5, SD = 0.4). Errors took a larger proportion of the completion time to correct on the written TMT-B, as inferred via linear modelling.
Conclusions: The oral and written SDMT appear to measure the same constructs. The oral and written TMT-B, however, measure only partially overlapping cognitive abilities, with the written version placing additional demands on spatial working memory and sustained attention. As such, the interpretation of deficits on oral TMT-B cannot draw straightforwardly upon literature underpinning the written task. The correlation between the oral and written TMT-B in our clinical sample was also weaker than reported elsewhere in healthy samples. This is likely driven, at least in part, by the higher error rates in our clinical cohort: as more errors are made more time is spent correcting those errors, confounding administrative and cognitive determinants of performance, potentially degrading reliability based on completion time. Our data also point to the importance of considering total errors when interpreting oral TMT-B performance in clinical settings.
References:_x000D_
1. Mrazik, Millis, Drane. The oral trail making test: Effects of age and concurrent validity. Arch Clin Neuropsych. 2010;25:236-243. _x000D_
2. Ricker, Axelrod. Analysis of an oral paradigm for the trail making test. Assessment. 1994;1(1):47-51._x000D_
Funding: This project was supported by an Australian Government Medical Research Future Fund Frontier Health and Medical Research Program Stage One grant (MRFF75908).