A-096 Reliable Change Indices as a Measure of Neurocognitive Change following Deep Brain Stimulation for Essential Tremor

Abstract

Abstract Objective Deep brain stimulation (DBS) is a widely used treatment for essential tremor (ET). To assess for neurocognitive decline following DBS, most studies use statistical methods that directly compare changes in test scores between pre- and post-surgical evaluations. By contrast, reliable change scores are calculated using regression-based models that account for practice effect and systematic error that can occur between repeat test administrations. We sought to determine the utility of reliable change scores in monitoring neuropsychological function following DBS. Method Twenty-eight ET patients (M age = 70.2 ± 6.3, 57% female) completed neuropsychological evaluations at an outpatient clinic 6.4 ± 3.6 months before and 6.7 ± 1.9 months after DBS placement within the ventral intermediate nucleus of the thalamus (71% left-sided). Wilcoxon signed rank tests were used to identify differences in performance using absolute change versus reliable change scores. Results There were no significant absolute differences between pre- and post-surgery scores on tests of attention, processing speed, executive function, object naming, verbal fluency, or learning and memory. By contrast, significant differences in reliable change scores from zero were identified on tests of phonemic fluency (p < .001), semantic fluency (p = .05), and verbal learning (p = .005). Conclusions Analyses that used reliable change scores identified post-surgical declines that were not evident in traditional statistical comparisons. Results suggest that reliable change indices are useful tools for monitoring changes in neurocognitive functions that can occur following DBS and related neuromodulation treatments.