Apparatus for treating neurological disorders by means of chronic adaptive brain stimulation as a function of local biopotentials

#The object of the present invention is an apparatus for treating neurological disorders by means of adaptive electro-stimulation.

#The invention relates to a system of feedbacked deep brain stimulation which is able to detect biopotentials from the stimulating electrode or by adjacent electrodes, to correlate such signals to the stimulation effects and feedback the stimulus parameters in order to optimize the therapy. Under local biopotentials, the electrical potentials produced by groups of neurons proximate the recording and stimulation electrodes are meant. As it is known the Deep Brain Stimulation (or DBS) is a therapeutic method based upon the modulation of the activity of structures of the central nervous system by means of the chronic electric stimulation supplied locally. The electrodes are implanted for treating the disorders of movement, epilepsy, headache, some psychiatric and pain disorders, by means of a stereotactic neurosurgical procedure. The methodology allows improving the patients to the benefit of the functional autonomy and the life quality. Since currently the Parkinson Disease is the disorder therefor the methodology use is consolidated, the present invention will be mainly referred thereto. The surgical treatment of the Parkinson disease historically started with lesional ablative procedures such as the pallidotomy and the thalamotomy. With the arrival of L-Dopa pharmacological treatment during the '70s, one observed a progressive abandonment of the surgical therapy. It was then taken into account again around mid '80s, with the pioneer studies of Benabid and Pollack in Grenoble, who proposed the high-frequency brain stimulation methodology. The principle is that of functional inactivation of the target structure. At first DBS had as targets the thalamic nuclei for the treatment of the Essential Tremor, then it was also used in the inner globus pallidus and in the subthalamic nucleus for the dystonia and the Parkinson disease. The system implantation procedure is relatively sure, little invasive and, at least in the Parkinson disease, it is carried out under local anesthesia. Once detected the target structure, one proceeds with the stereotactic localization thereof with the procedures of pre-surgical identification mainly based upon the encephalon's computed tomography and magnetic resonance. Subsequently, one proceeds with the trapanation of the cranial theca by inserting into the brain parenchyma exploring electrodes for the intra-surgical monitoring which allow recording the cellular activity during the systems of adaptive stimulation feedback by physiological signals. The U.S. Pat. No. 6,480,743, in the name of Benjamin D. et al., describes an adaptive stimulation system, in case equipped with a single electro-catheter, which analyses the electro-encephalographic signals to detect the presence of epileptic crises and consequently it activates a brain stimulation apt to inhibit the epeleictogen focus before the clinical crisis. However, such methodology excludes the in-chronic stimulation, necessary for the Parkinson disease, not providing any system for the contemporary recording of local biopotentials from the stimulating electrodes or from contiguous electrodes. The U.S. Pat. No. 5,683,422, in the name of Rise, describes a deep brain stimulation system, currently utilized as definitive implantation for the Parkinson's disease, which in case is feedback by a signal generated by sensors in case integrated in the same stimulation electro-catheter. Such sensors measure the superexcitation of a subthalamus portion proximate the stimulation site. In the preferred configuration such superexcitation is measured through an electro-chemical sensor which generates an electric signal utilized for feedbacking the stimulation coupled to an analog-to-digital converter by means of two conductors. The method proposed by Rise differs substantially from what proposed hereinafter in that it is based upon the use of an electro-chemical/biochemical, and not bioelectric, signal. The limits of the Rise invention are given by the nature of the electro-chemical signals therefor, apart from the currently available partial information about the biochemical processes of the nervous tissue in relation to the phenomenology of the Parkinson's disease, there is a latency time, given by the current technologies and by the tissue physiology, between the alterations of the subject's pathologic state and the tissue biochemical variations which makes difficult a sufficiently quick feedback stimulation avoiding system oscillations. On the contrary, the use of local biopotentials, the features thereof correlated to subject's pathologic states are known more in details, involves a minimum latency between the modification of the patient's clinic conditions and the time wherein the variation of the local biopotentials can be detected. In order to measure such local biopotentials, a system for removing the artefact not mentioned in the Rise's claims is strictly necessary, therefore the present invention provides important innovation features to the method proposed by Rise. Additional features and advantages will be more evident from the detailed description of a preferred, but not exclusive, embodiment of an apparatus for treating neurological disorders according to the present invention. Such description will be given hereinafter by referring to the enclosed drawings, provided by way of example and not for limitative purposes, wherein:

#FIG. 1 shows a schematic view of the apparatus for treating the neurological disorders by means of brain stimulation according to the invention;

#FIG. 2 shows a possible electric stimulus signal sent to a patient's brain;

#FIG. 3 shows the stimulus artefact received by the apparatus after the initial stimulating signal sending;

#By referring to the mentioned figures, an apparatus for treating neurological disorders by means of brain stimulation has been designated as a whole with 100.

#In particular, the apparatus illustrated in FIG. 1 is suitable for the feedbacked deep brain stimulation able to detect biopotentials from the stimulating electrode or from contiguous electrodes, for correlating such signals to the stimulation effects and for feedbacking the stimulus parameters in order to optimize the therapy onto the patient.

#The apparatus described and represented hereinafter has been mainly developed for the chronic treatment (that is with stimulating signals substantially sent continuously) of the Parkinson's disease, although the same apparatus is not to be considered limited to such particular application.