Packaging Architecture for an Implanted System that Monitors Brain Activity and Applies Therapeutic Stimulation

Abstract

Deep brain stimulation therapies for Parkinson's disease utilize hardware that, from a packaging perspective, resembles those that are used in cardiac pacemakers. A hermetic package that contains stimulation electronics and a primary battery supply is implanted under the scalp into a recess formed in the skull. Stimulation probes, each with up to four electrodes, are inserted into the brain and connected to the electronics package via a plug and cable system. Unlike single-target devices such as cochlear implants and pacemakers, achieving this type of neuropsychiatric therapy requires the ability to record and stimulate in multiple and distributive areas of the brain, both cortical and subcortical. By contrast, the closed-loop neural stimulator being developed under the DARPA SUBNETS program utilizes probes, each of which carries up to 64 electrodes that can be switched between recording and stimulation functions. This capability necessitates locating low-noise amplifiers, switching and communication electronics in close proximity to each probe site. Each of these satellite electronics packages requires 10 electrical connections to the hub package, which significantly increases the complexity of the interconnect system relative to the current practice. The power requirements of this system preclude the use of a primary battery supply, so a large lithium ion battery is used, with a recharging coil and electronics. The hub system is composed of a connector header, electronics package, and battery pack that are fabricated separately and are interconnected by a flex circuit board, to allow it to conform to the skull for implanting. The standardized feedthrough substrate on the satellite, which can interface with multiple types of electrodes, along the system being reconfigurable, enables our architecture to support this new clinical research. It also allows the clinician to select satellite-electrode system based on a patient's needs, thus providing a customized, patient-specific therapeutic system. In this article, we have described the various packaging components of this system and the design considerations that drove our technology choices.