Predictors of battery life for the Activa Soletra 7426 Neurostimulator.

DBS is increasingly used for Parkinson's disease, essential tremor and other movement disorders. The advertised battery life for Medtronic implantable pulse generators is 4-5 years, but can vary markedly. Theoretical formulas exist to predict battery life as a function of parameter setting, but almost no empiric confirmation of these predictions has been reported. We identified all battery replacements done for actual expired batteries and low voltage batteries. Demographic data were collected and the adjustable settings over the entire life of that battery were formulated longitudinally. The individual contributions of co-variables on the longevity of IPG devices were assessed by survival analysis based on the Kaplan-Meier estimator and log rank test. We have replaced a total of 122 batteries in 73 patients, 50 males (42 PD, 29 ET, two dystonias, one multiple sclerosis). The median life of these replaced batteries was 37.4+/-17.3 months [range: 4-93 months]. The batteries that completely expired were actually replaced sooner at 31.7+/-14.3 months [range: 4-74 months]. In this group, the main predictors of a shorter battery life were greater amplitude (p=0.002), pulse width (p=0.026), and not using exclusive bipolar settings (p=0.029). The implant location, underlying disease, and sex did not affect battery life. Battery life varied but was generally consistent with published predictors.