Authors :
Presenting Author: Taylor Jones, – University of Tennessee Health Science Center, Le Bonheur Children's Hospital, Memphis TN
Talitha Boardman, BS – Univ of Tenneessee Health Science Center, Le Bonheur Children's Hospital Neuroscience Institute; Savannah Gibbs, BS – Department of Psychology – Middle Tennessee State University, Murfreesboro, TN; Shalini Narayana, PhD – Professor, Pediatrics, Univ of Tenneessee Health Science Center, Le Bonheur Children's Hospital Neuroscience Institute; James Wheless, MD – Professor, Pediatrics, University of Tennessee Health Science Center, Le Bonheur Children's Hospital Neuroscience Institute
Rationale: Transcranial Magnetic Stimulation (TMS) is a non-invasive language mapping technique that is being increasingly implemented in pediatric epilepsy centers to identify key areas of language. TMS does this by temporarily disrupting cortical function, causing speech errors during picture-naming tasks. The frequency, region, and classification of these errors are used to calculate language laterality index (LI), crucial information in neurosurgical planning. In this study, we longitudinally analyzed change in laterality index to understand the effects that age of seizure onset and surgical intervention have on language plasticity.
Methods: In a retrospective database review, we identified 18 patients with intractable epilepsy whose laterality index was measured at two timepoints. Patients were categorized by age of seizure onset, before and after the age of 10 years. They were also grouped by whether they underwent surgical intervention between the TMS assessments of laterality (Table 1). Repeated measures ANCOVA and profile plots were used to explore the significance of these between-subjects factors. Age was considered as a covariate at each level of assessment.
Results: Analysis of laterality index by age of seizure onset showed that patients with a seizure onset before the age of 10 years experienced typical language development in the left hemisphere. In another analysis of laterality index – this time by the factor of intervention – we observed that patients who received intervention between measures of laterality became more dominant in the left hemisphere while those who did not remained more bilateral. When factored together, age of seizure onset and intervention had a significant effect on the sample group (p = .041). Early onset and intervention caused a drastic increase in left-sided lateralization; while late onset and no intervention caused a considerable decrease in left-sided lateralization and a greater recruitment of right hemisphere regions (Figure 1).
Conclusions: Our findings shed light on the potential of TMS as a valuable tool in understanding the mechanisms of language plasticity and informing clinical decisions regarding the optimal timing for surgical intervention in patients with epilepsy. The joint effect of age of seizure onset and intervention suggests that earlier interventions likely facilitate normal language development, while ongoing epilepsy burden may lead to reorganization. While onset age and intervention were not significant factors individually, we anticipate that our findings can be corroborated by larger datasets. Monitoring laterality changes over multiple timepoints in individuals using TMS is a viable approach for constructing models of language plasticity and clarifying the compensatory behaviors of language development in response to epilepsy.
Funding: N/A