Field of the Invention
This invention pertains in general to the field of stimulation devices, and especially to conductive implantable stimulation devices.
Description of the Prior Art
Transcranial direct current stimulation (tDCS) is a non-invasive technique that can be used to modulate brain activity and to promote neuroplastic changes for therapeutic aims. Recent advances include therapeutic success in major depression treatment, potential in chronic pain treatment and stroke rehabilitation. Specific targeting of electrical current is hampered by the skull, which has poor conductivity. This is a well-known problem in brain bio-electromagnetism. The skull thickness and conductivity properties are unknown, which makes the prediction of current flow into the brain a very difficult task that require detailed measurements and modelling of electrical properties of the anatomy and structure of brain and skull.
Moreover, in animal studies with tDCS has been shown that nearly 50% of the electrical current of tDCS does not reach the brain, but rather flows from anode to cathode on the skull 11 surface. Therefore, the output current from the device needs to be increased to reach a desired target levels in the target brain tissue. This, in turn, creates complications such as adverse sensations, skin irritation and possibly skin burns.
In chronic diseases, such as Parkinson's disease or chronic pain, one potential treatment approach is to implant a deep brain stimulation (DBS) device (Parkinson's) or an epidural motor cortex stimulator (MCS, chronic pain). In DBS, the electrodes are installed close to deep brain structures (subthalamic nucleus or globus pallidus) to specifically target these structures. In MCS, the aim is to reach specific cortical areas to modulate cortical activity associated with the pain relief. Installation of a DBS electrode is expensive and can lead to serious adverse effects, such as stroke, cerebral infections. Moreover, technically complicated equipment requires periodical maintenance, battery charging or changing that needs to be completed in an operation. Similar complications are present in the MCS implantation.
Thus, a need for an improved stimulation device solving or at least mitigating the above problems is needed.