Management of deep brain stimulator battery failure: battery estimators, charge density, and importance of clinical symptoms.

OBJECTIVE: We aimed in this investigation to study deep brain stimulation (DBS) battery drain with special attention directed toward patient symptoms prior to and following battery replacement.
BACKGROUND: Previously our group developed web-based calculators and smart phone applications to estimate DBS battery life (http://mdc.mbi.ufl.edu/surgery/dbs-battery-estimator).
METHODS: A cohort of 320 patients undergoing DBS battery replacement from 2002-2012 were included in an IRB approved study. Statistical analysis was performed using SPSS 20.0 (IBM, Armonk, NY).
RESULTS: The mean charge density for treatment of Parkinson's disease was 7.2 µC/cm(2)/phase (SD = 3.82), for dystonia was 17.5 µC/cm(2)/phase (SD = 8.53), for essential tremor was 8.3 µC/cm(2)/phase (SD = 4.85), and for OCD was 18.0 µC/cm(2)/phase (SD = 4.35). There was a significant relationship between charge density and battery life (r = -.59, p<.001), as well as total power and battery life (r = -.64, p<.001). The UF estimator (r = .67, p<.001) and the Medtronic helpline (r = .74, p<.001) predictions of battery life were significantly positively associated with actual battery life. Battery status indicators on Soletra and Kinetra were poor predictors of battery life. In 38 cases, the symptoms improved following a battery change, suggesting that the neurostimulator was likely responsible for symptom worsening. For these cases, both the UF estimator and the Medtronic helpline were significantly correlated with battery life (r = .65 and r = .70, respectively, both p<.001).
CONCLUSIONS: Battery estimations, charge density, total power and clinical symptoms were important factors. The observation of clinical worsening that was rescued following neurostimulator replacement reinforces the notion that changes in clinical symptoms can be associated with battery drain.