Introduction: Accelerometery can be used to objectively monitor tremor, though lack of clinical validity and cumbersome devices have limited widespread adoption. With ongoing maturity, smartphones and wearable devices are shaping personalized medicine, especially in movement disorders. The current study reviews the correlation of intraoperative tremor as measured by an iPhone© accelerometer to postoperative tremor, functional outcomes and quality of life.
Methods: The authors retrospectively reviewed a prospective series of seven consecutive patients (13 hemispheres) who underwent tremor measurements using a publicly available accelerometer app (ParkinsonMeter) for the iPhone©. Tremor magnitude was measured preoperatively and intraoperatively during Vim DBS surgery. Patients were clinically evaluated during a median follow-up period of 13.6 (range 5.9 – 18.9) months using the Clinical Rating Scale for Tremor and Quality of Life in Essential Tremor Questionnaire.
Results: All but one patient (unilateral) presented with bilateral medically refractory action-induced tremor at an average age of 65.6. Linear regression analysis of CRST and QUEST scores compared to tremor measurements revealed a statistically significant correlation between improvement in total CRST score and intraoperative change in tremor score (slope=0.5, p=0.0361, R2=0.3). Analysis of individual CRST components (A: Tremor Severity; B: Motor Tasks; and C: Functional Disabilities) illustrated a positive correlation between change in tremor score and each component, though this did not reach statistical significance (A: slope=0.53, p=0.14, R2=0.14; B: slope=0.65, p=0.069, R2=0.2 C: slope=0.65, p=0.058, R =0.22). Similarly, a positive correlation between change in tremor and quality of life was observed (slope=0.28, p=0.65; R2=0.03).
Conclusions: In the current study, patients exhibiting the greatest improvement in intraoperative tremor showed a statistically significant improvement in overall disease burden and a positive correlation with quality of life. This data suggests that simple devices can be used intraoperatively to evaluate tremor quantitatively and possibly assist with lead placement to improve outcome.
Patient Care: The current study provides evidence that commercially available smartphone hardware and software technology can be used intraoperatively to evaluate tremor during DBS surgery for ET patients and that this measurement correlates with subjective and objective outcomes. With further validation, this simple technique could provide insight into optimizing intraoperative electrode localization and further improve outcomes of DBS surgery.
Learning Objectives: 1. Understand that intraoperative accelerometer measurement is simple and effective and can easily be implemented during DBS surgery
2. Acknowledge that intraoperative tremor measurement correlates with postoperative quality of life assessment and tremor assessment
3. Recognize that intraoperative accelerometer measurement predicts outcome in ET patients undergoing DBS and with further validation potentially could be used to assist with electrode localization
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