Butson and McIntyre
(from the Cleveland Clinic Foundation) published in 2006 an article in which they describe the results of a computer calculation of the consequences of the electrode design on the (electric) field shape – which is the region receiving electrical stimulation. Butson and McIntyre calculated the result of changing the dimensions of the supporting wand (that is, the thin, drinking straw-like structure that is implanted in the brain, which Medtronic calls “lead”) and electrode (that is, the ring-like conductive surface at the extremity of the implanted lead), but they did not consider the possibility of asymmetric field shapes, let alone the possibility of changes on the electrode shape after the surgery is completed and the lead fixed in place. Most likely such changes were not contemplated by the authors because they could not image it physically possible to depart from the Meditronic lead design: a long cylinder with four ring-like electrodes at the end. Butson and McIntyre’s calculation is limited to this constraint. Even with this limitation they show how a smaller diameter lead and long electrode could fit better the needs of a particular patient. Butson and McIntyre’s calculation is useful as an indication of the medical consequences of lead and electrode design on the stimulated area, even though their calculations were not carried to the ultimate consequences of asymmetrical fields.
Their article does not go to the ultimate advantages, which are asymmetric fields and post-surgery choice of field shape, that is, to create an arbitrary volume shape after the lead is fixed in place, also adapted to the particular positioning of the lead within the desired volume, both to correct for failure to insert the lead exactly on the target area, and to inherent locus asymmetries, possibilities that exist with the adoption of our invention, but not with current devices. Click here to see Butson & McIntyre Field Simulation
In this article, Kenneth Follett et al. publish the results of their statistics on side effects of DBS. The side effects probability depends on the implant locus, which in this study is either the globus pallidus interna (GPi) or the subthalamic nucleus (STN), and Follett’s article contains both numbers, separated for each locus and consequences. Depression frequency runs from 26% (GPi) to 37% (STN), speech problems frequency runs from 28% (GPi) to 35% (STN), and confused states frequency runs from 20% (GPi) to 22% (STN), for each, respectively (table 4, page 2088). Click here to see Kenneth et al. article
Index_101008 12:56 p.m.