Field of the invention

The invention is related to an electrode, which allows, after application on a skin, electrically stimulating suitable nerve plexus localized in a tissue under the skin. Preferably, the electrode is intended for stimulating nerves in lower limbs in treatment of dysfunction of lower urinary tract (urinary incontinence). Further, the invention relates to a detector for automatic adjusting of the neurostimulation pulses frequency to an optimum value. By using the detector it is possible to considerably raise the efficiency of neurostimulation, shorten and streamline duration of such a treatment.

Background of the invention

The existing treatment of urinary incontinence, which affects a substantial part of the population, has not been quite therapeutically successful to date, in spite of its accompanying complications and social impacts. Pharmacological treatment prevails, which is accompanied with frequent undesirable side effects and a gradually reducing efficiency. Surgical treatment in severe cases produces its interventional risks and possible subsequent urological problems.

New therapeutic possibilities were brought by so-called Stoller electrostimulation method (Stoller, M.: Needle stimulation (through the skin) for the treatment of incontinence. Quality care 16:1, 1998). The substance of this method is an introduction of a sterile needle (i.e. a needle electrode) to the close proximity of the nerve nervus tibialis above the ankle of the leg. Negative electric pulses are supplied to the needle, wherein the duration of the pulses is in the order of milliseconds and the current is in the order of mA. One exposition lasts usually half an hour and a therapeutic effect can be observed usually after 12 treatments. Nevertheless, Stoller method, even though only partly invasive, produces a number of application problems, possible side risks and especially painfulness for a patient. Problems consist especially in the necessity of a puncture of the stimulation needle into the closest proximity of nervus tibialis, the localization of which below dermal and muscular tissue can vary in individuals. Finding the effective position of the needle in relation to the nerve requires often several preliminary, tentative punctures at every exposition with a risk of nerve puncture and nerve damaging. Verification of the correct introduction of the needle is possible after reaching a small distance from the nerve according to the corresponding motor reflex on the toes. A repetition of punctures into the near or the same spots results often in traumatic damage of penetrated tissues with a possibility of inducing inflammations and necrosis. It was demonstrated in practice that a part of patients interrupted treatment just due to these painfulness aspects of progressively injured puncture spots.

The document US 5370671 describes an electrode for incontinence treatment. It is a vaginal electrode for electrostimulation of pelvic floor muscles. Electrodes of various types for medical usage, particularly for the application of electric signals on the skin, are described e.g. in US 2004/0225343, GB 2 418 364 or WO 2006/053366.

Problems and imperfections of the prior art techniques are removed by the electrode for fully non-invasive percutaneous neurostimulation treatment, especially urinary incontinence treatment, which is described below.

Neurostimulation treatment as mentioned above generally belongs to electrostimulation techniques in which the electric pulses or oscillations are supplied through a fine electrode directly surgically introduced to the appropriate organ nerve or through the puncture of a needle, or by application of the electrode on the skin in the proximity of the appropriate nerve. Modulation of corresponding nerve control centres can be achieved by induced afference. The data about the success rate of such a modulation in scientific literature considerably differ and are dependent on the technique of stimulation, number of applications and especially on the physical parameters of used commercial apparatus. Their technical characteristics considerably differ in the shape, length (in the extent of two orders) and frequency (from 2 to the 100Hz) of the electric pulses. The reason is that neurological processes induced by the action of pulse current are not fully understood. Therefore in practice, the choice of frequencies is rather an intuitive choice, considerably dependent on individual constitution and other predispositions of patients. However, a wrong assessment may result in an unsatisfactory therapeutic outcome. Hence, there is a strong demand of a device which would help to determine optimal frequency, length and shape of stimulation pulses in electromodulation treatment. This demand is solved by a detector of reflective movements described below.

Summary of the invention The objective of the present invention was to design an electrode, which would be convenient for fully non-invasive electric nerves stimulation, especially lower limb nerves, with a therapeutic efficiency at least such as achieved by the invasive Stoller method. The objective was achieved by constructing the electrode, which is in more detail described further below and its preferred embodiment is demonstrated in Example 1. A research of the distribution of electromagnetic fields in human tissues in the surroundings of nerve paths suitable for electric stimulation, carried out by the inventors, resulted in the development of the electrode with such a geometry that after placing to the skin enables creating of electric field with enough electric gradient even in considerable depth of some tissues. Sufficient potential gradient in the order of hundreds of millivolts is then capable of activating polarization of neural cells and formation of stimulation impulses transmitted afferently to higher nerve centres. It stems from the laws of physics that electromagnetic field intensity of the point electrode, in comparison with an infinitive area electrode, decreases with the second power of the distance. From the physiological point of view it is therefore not possible with a point electrode placed on the skin surface to increase arbitrarily the electric voltage in order to achieve the polarization of cells of deeper nerve pathways within a few millimetres in the tissue. The reasons are dermal nerve receptors, which in proximity of the high-powered electric field of the electrode would transmit strong painful stimuli, and the current flow would release heat energy destroying adjacent tissue cells. By studying and experimental measuring the conductivity features of tissues in the vicinity of nerve paths suitable for afferent neurostimulation and following neuromodulation and formation of the electric flow by strong magnetic field of intensities of several hundreds G (gauss) and by varying in geometry of the electrode, the compromise was found in the effect of electric pulses on the skin and subdermal tissue layers, that they would not be excited by the intensity of electric current sufficient to stimulating the deeper nerve paths. Especially suitable conditions were found in the area of lower and rear part of thigh and especially in popliteal fossa, where dividing branches of nervus ischiadicus traverse. On the basis of researches mentioned above the inventors designed and engineered the electrode, which fulfils the requirements for fully noninvasive electric stimulation with the same or higher therapeutic efficiency than Stoller method, without the necessity of painful and risky disturbing the tissues by punctures. High efficiency in incontinency treatment while using electrode according to the present invention was confirmed in clinical trials. The treatments were without any undesirable side effects and unpleasant sensations of the treated persons.

The objective of the invention was then achieved by constructing the electrode, which is further generally characterized and the advantageous embodiment of which is described in Example 1.

Hence, the subject-matter of the invention is the electrode for use in percutaneous neurostimulation treatment, especially in urinary incontinence treatment. However, the person skilled in the art will appreciate that the electrode according to present invention can be used also for other kinds of electric neurostimulation treatment, e.g. for treatment of pain.

The electrode comprises a hemispherical contact member, which is the electrode part intended for contact with body surfaces above stimulated nerves and for creation of required distribution of electromagnetic field in tissue. Hemispherical contact member is by its base fixed, by soldering, to the electrode core in the form of a pivot, whereas the hemispherical contact member and the core are conductively joined. A cylindrical permanent magnet is co-axially mounted (pressed on) on the core. For the correct function, i.e. the influence upon the electric field, the permanent magnet must be oriented with its northern pole into the tissue. It means that the magnet is mounted in such a way that it directs by its northern pole to the hemispherical contact member. The term„hemispherical" in the context of„hemispherical contact member" does not have the literal meaning for description of a body shaped as an exact half ball, but it is understood also as a smaller part of a ball, ball segment, the base of which can have a radius smaller than the radius of a corresponding ball cap, or a corresponding ball. The hemispherical contact member of the electrode is made from a biologically inert metal, such as gold, titanium, silver or alloys of these metals, preferably it is made from silver. The contact area of the hemispherical contact member can preferably have a size of 0.5 to

2 2

1.5 cm , more preferably 0.8 to 1.0 cm .

The core of the electrode is made from metal, preferably stainless steel (anticoro) steel used for surgical tools.

The cylindrical permanent magnet is made from a highly magnetizable material, preferably the AINiCo alloy. The material for the magnet must be capable of high degree magnetization and must not corrode during washing and disinfection, or sterilization of the electrode. The cylindrical permanent magnet suitable for the electrode according to the invention exhibits the magnetic surface inductance (i.e. the intensity on the surface of the pole) of at least 300 G, preferably higher values such e.g. 400 G.

A washer in the form of annulus is mounted to the core between the base of the hemispherical contact member and the magnet. The washer prevents infiltration of liquids (e.g. sweat) to the slot between the electrode and the magnet. The washer is made from a biologically inert material, e.g. silicone or teflon, preferably from teflon.

The preferred materials mentioned above are biologically compatible and conform to standards for medical devices, which must be disinfected, or sterilized. The person skilled in the art is aware of the fact that there are many other suitable materials which can be used. The core of the electrode can be provided by a thread on the side opposite to the contact member, which allows mounting of the locking nut, which together with the stabilizing disc may fix the electrode to the carrier means, e.g. the fixation strap. The end part of the core opposite to the contact member is adapted to be connected with an electric cord, e.g. comprises an adapter for setting a cord transmitting electrical signal from the electrostimulation apparatus. The electrode according to the invention may further comprise a stabilizing disc, by means of which it can be firmly fixed to the means serving for fixation of the electrode on the limb, advantageously to the fixation strap. The stabilizing disc is made e.g. from polymethyl methacrylate, polycarbonate, PVC, PE or PET, preferably from a transparent material. The fixation strap can be, as well as the stabilizing disc, easily detachable from the core. The strap is preferably elastic and can be made e.g. from textile or plastic fibres, or their combination.

The Example 1 presents a preferred embodiment of the electrode for electric stimulation of nerve plexus of lower limbs in treatment of urinary incontinence. The person skilled in the art will appreciate that the electrode described herein can be modified in various ways without diverting from the features of the electrode defined in the patent claims.

Further, the invention relates to the electrostimulation device, preferably neurostimulation device, which comprises the electrode for percutaneous electrostimulation as described above. Further, the present application is related to a detector of reflective movements, which detects and reads out motor reflexes of muscle groups that are innerved by nerve path affected by electric stimulation currents. In the detector, reflective movement evokes an electric pulse that is led from the output connector of the detector to the electronic apparatus, which generates stimulation pulses, and initiates the starting of the next stimulation pulse. By using the detector of reflective movements in the electrostimulation, positive feedback is formed, so that the whole process is constantly repeated and is controlled by a natural process that depends on the rate of transmission of the impulse in the initiated nerve paths and the resulting muscle reflection. The process will stabilize on characteristic frequency, shape and length of pulses corresponding to the optimum and natural neurophysiological transmission conditions of every stimulated individual and forms optimum circumstances for effective afferent modulation of corresponding nerve control centres participating in incontinence causes. The detector can adapted by the value of the output signal to the most of commercially available stimulation apparatus and thus to optimise substantially their stimulation efficiency and thereby successfulness of the treatment. The detector according to the present invention for use in electric neuromodulation treatment, preferably urinary incontinence treatment, is intended for touch reading of reflective movements of muscle groups and generation of electric signal for feedback control of frequency, shape and length of stimulation pulse in the resonance regime. The detector allows automatic adjustment of all parameters of neurostimulation pulses on the optimum value, which matches the resonance of stimulation electric impulses with induced motor reflexes of corresponding muscle groups.

The detector comprises a ball placed in a tubular case, which is closed at one end using non-elastic plug and on the other end a piezoelectric sensor is located. The diameter of the ball is only a little smaller than the inside diameter of the tubular case, so that the ball is able to move freely in the tubular case along the longitudinal axis by rolling and sliding (gliding) motions. The tubular case comprising the ball is built into the outer casing (together with electronic components), which is adapted for fixation on a reflective active part of limb. If the detector is fixed on the reflective active part of limb, then the movement of the limb initiates the motion of the ball and the ball evokes an electrical signal by hitting the piezoelectric sensor. The signal generated this way can be used for feedback control of the electric stimulation pulse generator. The non-elastic plug is inserted in the tubular case in a sliding way along the longitudinal axis of the tube so it is possible to adjust the current length of the ball motion track. The adjustment of the length of the ball motion track allows setting the respective resonance frequency out of the region of stimulation resonance frequency.

The signal from the piezoelectric sensor is led to the electronic part of the detector, which comprises a preamplifier/amplifier and which allows transmission of a modified signal to the electrostimulation apparatus. Therefore, the detector includes also suitable connecting means for connecting the electrostimulation apparatus. With respect to the electronic part of detector, its construction is a routine matter for the person skilled in the art of electronics.

The ball can be made from any suitable material such as metal, glass, plastic, however, it must have a sufficient weight to generate signal after hitting the piezoelectric crystal and must be finished precisely enough in order to move within the tubular case without restrains. Preferably the ball is made from steel. Advantageously the ball-bearing ball is used which is precisely finished and polished, and additionally, such balls are easily available virtually in any sizes.

The tubular case can be made from any suitable material such as metal, glass, plastic, however, the interior surfaces of the case must be finished precisely enough and must be smooth enough not to obstruct the ball movement. Preferably the tubular case is transparent, which allows visual checking of the free mobility of the ball. Hence, the preferred tubular case is made from glass. Advantageously a glass tube originally intended for a rotameter (rotary gas flowmeter) which is precisely grinded inside is used.

In a preferred embodiment the glass tube with the inner diameter of 5 mm and a steel ball with a diameter of 4.9 mm were used.

The piezoelectric sensor is preferably a piezoelectric crystal, e.g. quartz crystal. Suitable piezoelectric crystals are readily available. In a preferred embodiment the piezoelectric crystal (from an ordinary lighter) of the sizes 5 mm x 5 mm x 8 mm was used, generating electric pulse about 5 to 8 V after the ball hit. The non-elastic plug is made from a material which is preferably acoustic damping. A preferred plug is made from foam polyethylene.

The person skilled in the art will readily find other suitable materials for production of the components of the detector described above, which may be used while maintaining the functionality of the detector. The detector according to the present invention is useful in various electromodulation treatments, especially in electromodulation treatment of urinary incontinence.

The person skilled in the art is aware of the fact that the detector may be modified in various ways without departing from the detector defined in patent claims.

Further, the present invention relates to the electrostimulation device, preferably neurostimulation device, which comprises the detector of reflective movements described above.

In addition, the present invention relates also to the electrostimulation device, preferably neurostimulation device, which comprises the electrode for percutaneous electrostimulation and the detector of reflective movements, both as described above. Brief description of the drawings

Fig. 1: Scheme of the neurostimulation electrode comprising the hemispherical contact member, core and permanent magnet. A. Longitudinal central section. B. Top view.

Fig. 2: Scheme of the detector of reflective movements for use in resonance neuromodulation treatment.

Examples of the embodiments of the invention Example 1

A preferred embodiment of the electrode according to the invention is demonstrated on Fig. 1. The hemispherical contact member I for contacting the electrode with a skin surface is conductively joined to the core 4 of the electrode. The hemispherical contact member 1 is made from silver. The hemispherical contact member has a surface of 0.8 to 1.0 cm ² .

The electrode core 4 shaped as a cylinder is made from stainless steel. The junction of the contact member 1 with the electrode core 4 is made by soldering with silver solder. At the end opposite to the contact member 1, the core 4 is provided by a thread (for setting a nut 7) and ended with the adapter 9 for connecting of the wire supplying electrical signal from the electrostimulation apparatus. The permanent magnet 3 in the form of a hollow cylinder made from the highly magnetizable AINiCo alloy is mounted (pressed on) on the core 4. The base of the contact member 1 is separated (watertight) from the magnet 3 by the annular washer 2, which is made from teflon. The magnet 3 is oriented such that its north pole is directed to the end with the hemispherical contact member h

The electrode assembly consisting of elements I, 2, 3, 4 and_9 is further provided with the stabilizing disc 6 _± which is made from transparent plastic, and by the help of the nut 7 and the washer 8 is fixed to the elastic strap 5, which enables fixing the electrode on the selected position on the limb. The elastic strap is made from POP (polypropylene) and is provided with a fastener. Example 2

Fig. 2 schematically represents the detector of reflective movements for use in resonance neurostimulation, particularly intended for urinary incontinence treatment.

The basis of the detector is the tubular case 12 containing the ball H. At one end, the tube 12 is closed by the piezoelectric crystal 14 and on the other end by the non-elastic plug 13. The tube 12 is a glass tube intended for use in rotary flowmeter, which has a precisely grinded and smooth inner surface. The ball H is a steel ball for bearings, which has a smoothed surface. The inside diameter of the tube 12 is 5 mm, the diameter of the ball Π. is 4.9 mm, so that when deflecting the tube 12 from its horizontal position the ball ϋ is able to move freely in the tube 12 by rolling, or sliding motions. The plug 13 is made from foam polyethylene. The length of the motion track of the ball H is adjustable by shifting the plug 13 so that the respective resonance frequency of the detector lay as far as possible from the frequencies of the stimulation signal.

The piezoelectric crystal 14 which was used is the piezoelectric crystal for ordinary gas lighters with a size of about 5 mm x 5 mm x 8 mm. The crystal 14,_after hitting by the ball 11, generates an electric pulse of about 5 to 8 V.

The tube 12 is built into the casing 18, which enables fixing the detector to the reflectively active part of the limb by using an elastic bandage. By the transmission of the reflective movement of the limb on the casing 1_8, the ball I I starts its motion and in one of the extreme positions will hit the crystal 14, whereby it induces electrical signal, while in the other extreme position it will hit the plug 13, where it stops without any acoustic manifestation. The next reflexive movement of the limb causes a new hit of the ball 11 on the piezoelectric crystal 14. This process repeats in the rhythm of reflective movements and electrical signal from the piezoelectric crystal 14 is led by the connection 15 to the electronic preamplifier 7, where it is modified to the suitable carrying signal form and is further led by connection 16 to the output connector 19 for connecting of the electrostimulation apparatus.