GENERAL INFORMATION:
NEUROSTIMULATORS, NEUROIMPLANTS AND TULGAR IMPLANTS

Neurostimulation is a process, by which nerves partially loosing their function as a result of disease or travma, are depolized by artificial electrical pulses for regeneration. Neuro-implant is a clinical tool that electronically stimulates the nerves system under the skin following surgery. Therapeutic signals, used for this purpose, must be consistent with the nature of human neurophysiology [1].

Transcutaneous Electrical Nerve Stimulators (TENS) have long been used in clinical applications [2-3]. Implanted electrical stimulators were primarily developed for the management of pain [4]. In case of persistent and extensive pain, transcutaneous stimulation is not adequate due to the need for multiple electrode placement and increased skin impedance. In order more effectively to cover the painful area, direct stimulation of the spinal cord is necessary via an implantable electrode system [5]. Further clinical studies showed that, in addition to control of pain, this method could also be effective on other conditions, e.g. vagus nerve stimulation for the management of epilepsy, depression and alzheimer disease, phrenic nerve stimulation for diaphramme pacing in breathing disables, deep brain stimulation to control parkinson’s disease [6-10].

To date, almost all implantable stimulators have exclusively been manufactured by a few US companies, and mainly used in USA, Canada, Japan, Australia and Western European countries (England, Germany, France, Italy, Spain, Holland, Belgium, Austria, Sweeden).

The existing implants operate utilizing either radio-frequency (RF) transmission or fully implantation technics [11]. In both case, implantable parts include miniature electronic components. Totally implantable systems, in addition, have a long-life battery that evantually (2-5 years) needs replacement by another surgical procedure.

A fundamental requirement for successful neurostimulation is to deliver and maintain effective stimulation to the appropriate regions of the body, stimulation paraesthesia must cover completely the area of target neurons, and it must not trigger unwanted segmental sensations [12-14]. There have been many reports about the successful application of neuroimplants which have been around for 40 years, but some complaints of their performance have also been voiced [15]. The problems encountered with the present systems can be classified as follows: 1) Breakdown in the electronic components: The existing systems rely on the implantation of a circuit which include electronic components and, as component failure is not unknown, patients can be subjected to further surgery to replace a defective part. 2) Expiration of battery: totally implantable devices powered by a long-life battery that eventually needs replacement at approximately 2-5 year intervals, apart from component failure, also require extra surgery to replace the used battery. 3) Programming difficulties: patients wearing a fully implantable system have to go to hospital at certain times for the arrangement of stimulation parameters, and sometimes there are difficulties in externally programming the implanted circuit. 4) Expense of the equipment: The high cost of commercially available implants ($10000-50000) severely limits widespread use of this clinically approved method.

To overcome these problems, encountered with the present implants, a new system, namely the tulgar implant, based on trans-dermal inductive coupling principles, has been developed [16-17]. The new system, that is externally powered and controlled, consists of implanted compact passive element - electrode and external active element – stimulator. Therapeutic signals produced by the external stimulator unit are linked to the active element, then they are transmitted by inductive coupling across the skin of patient. The main goal of the present invention is that there are neither any electronic components nor a battery in the internal part of the system. Therefore, no breakdown due to component failure should be expected, and patients can use such a system along life-time. On the other hand, 80 % reduction in size, that is very important from the surgical point of view, especially in children, has been achieved (the passive element is of 21 mm in diameter, and 6 mm in height). When the power of battery goes down, the system can easily be recharged using the portable charger unit provided, as in a gsm mobile phone. The new system is versatile and can be used to transmit any form of electro-therapeutic signals which are known to be safe and effective [18-20]. In addition to solutions of the problems of the present implants, the other important advantage provided by the new system is the elimination of unwanted electrolysis phenomena which may lead to tissue necrosis [21]. Because the signal transmitted by RF based implants is mono-phasic in nature which means involment of direct current (DC), whereas pulses induced by the new system are DC free. All these factors reduce the cost (at least 2 fold) of the new implant system, while conveying the additional advantages of safety and reliability.

Tulgar implants were based on a 7-step long-term study project: 1) Development of prototype, 2) Laboratuary tests, 3) Safety tests, 4) Pre-clinical tests, 5) Preparation of clinical models that can be applied in the living tissue, 6) Animal tests [22], 7) Pilot implantation in human body. After the completion of EMC (electromagnetic compitability) and safety tests in accordance with EN 45502-1-2 and EN 60601-1-2-4 standards, full quality assurance certificates (CE, ISO 9001:2000, EN ISO 13485) have been obtained from a Notified Body namely EZU (number: 1014) located in European Community, Chzeck Republic. Then all products have been entered to Medical Device Registration System of Republic of Turkey, General Management of Treatment Services, Department of Medical Devices, Division of Market Monitoring. Therefore all necessary legal procedure for serial manufacturing has been undertaken. Also, Tulgar Neuro-Implant System is already under international patent protection, Turkish (TR 2005 01692 B) and European Patent Certificates (1575665) and PCT (Patent Cooperation Treaty) report (PCT/TR 03/00092) are available. Top national patent award by Turkish Patent Institute has been given to Prof. Dr. Metin TULGAR, Founder and President of Neurotechnology Center, care/off Prime Minister of Turkey, Mr. Recep Tayyip Erdogan. Based upon thirty years of experience in the field, Professor TULGAR keeps working for Neurotechnology Center where he is also founder.

REFERENCES:

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