GB2518929A - Improvements in and relating to neurostimulating devices for treating pain, improving function and other nervous system related conditions - Google Patents

Abstract

A device 10 for treating chronic pain has one or more rounded stud electrodes 12 (diameter of 3-12 mm) mounted on a support for applying pressure to the electrodes so they indent a patients skin. Preferably the support includes rigid washers 16 of two to three times the diameter of the stud. The stud and washer assemblies may be mounted on a flexible strap having hook and loop patches 30 or may be secured to the patient by an elasticated adhesive fabric stretched over the patients skin. A signal generator, which may be mounted on the support, provides a stimulation signal to the electrodes. The signal may have a frequency of 1 Hz to 50Hz and a current of between 0.2 and 60 mA. The studs may be provided in a strip which can be cut to the required length. An earthing patch (reference electrode) 36 may be provided on the underside of the support.

Description

IMPROVEMENTS IN AND RELATING TO NEUROSTIMULATING DEVICES FOR

TREATING PAIN, IMPROVING FUNCTION AND OTHER NERVOUS SYSTEM

RELATED CONDITIONS

This invention relates to improvements in and relating to devices for treating acute and chronic pain, for cosmetic applications, relieving diseases that aetiologically have a functional or neural component, including gastrointestinal, rectal, urological, gynaecological, musculoskeletal, endocrine and nervous system disorders, to include malignant conditions. Such conditions and disorders will be referred herein and hereafter as the specified conditions' and the invention is described throughout this

specification in this context.

US patent no. 5,449,378 (Scouenbourg) describes a device for relieving chronic and acute pain, which includes a shapable electrode plate through which a plurality of electrodes are fixed and terminate, at their respective free ends, in pointed electrode tip portions for skin penetration. The electrodes are connected to a control unit designed to activate the electrodes. When pressure is applied, the electrode tip portions are designed to penetrate the isolating outer layers of the epidermis to stimulate the receptors of the skin.

In my earlier patent no. GB243521 7 I described the use of transcutaneous electrical stimulation to treat chronic pain and for cosmetic applications using multiple electrodes to apply low frequency, low current electrical stimulation to an identified area on a patient's body. I disclosed that such stimulation should be applied to an area that had been identified using a stimulating signal to a patient to detect a suitable and optimum position. The relief achieved was furthermore significantly improved where firm pressure was applied to the electrode(s) during the electrical stimulation process.

The same electrical currents and pulses described in my patent GB2435217 may be used as a basis for stimulation within the present application, though as in that previous patent, the parameters will be adjusted within the specified ranges to suit the patient and pain profile to achieve the best results. Thus, low, varied and higher frequencies may be employed according to a patient's condition and his or her response to the treatment.

An object of the invention is to provide improved means for applying firm pressure to a stud or studs in order to treat the specified conditions, with the option, when it is practical, to apply electrical stimulating pulses to the stud or studs to enhance the re Ii of.

This invention discloses and claims specific devices for applying sustained pressure to a single or to multiple stud electrodes adapted to be applied to various parts of the anatomy, and to applying electrical stimulating pulses in order to treat the specified conditions.

A device for treating the specified conditions in accordance with the invention comprises a firm, inelastic or semi-elastic, insulating support having one or more rounded or substantially hemispherically-or parabolically-shaped electrically-conducting metallic studs projecting from one side of the support, which support is arranged in use to be held firmly against a patient's skin by mechanical means as herein defined so that the studs indent the patient's skin, the studs being arranged for connection to a power source and a generator of electrical stimulating signals which in use apply the stimulating signals to the patient's skin whilst maintaining pressure on the skin.

In this specification and the attached claims mechanical means as herein defined' shall mean any one or more of the following means: -elastic or inelastic straps or the like, e.g. polymeric straps, forming a part of the support or attached to it and arranged to be attached around a patient's limb or body; -Velcro, or the like, patches on the support and arranged to hold the support firmly around a patient's limb or body part; -an adhesive coating arranged to allow the support to be removably stuck to a patient's skin so that the stud(s) are pressed firmly into the patient's skin or -a shaped or formed element arranged to fit tightly over a part of the body by stretching or strapping it in position in each separate case the mechanical means being arranged to hold the support firmly against the patient's skin so that the studs are pressed into the patient's skin; Electrical stimulation via the studs is an essential element of the treatment in order to achieve optimum results, though some relief may continue to be felt by a patient once the electrical stimulating signal has stopped due to the acupressure effect of the pressure of the studs on the patient's skin. Such relief may justify that the device remains in place between treatments with the appropriate electrical stimulating signal.

In some instances, the treatment not only provides significant relief over prolonged periods, but also has the additional benefit of improving function.

The invention extends to a method for treating the specified conditions using substantially hemispherical or parabolic studs projecting from a firm support that is pressed against a patient's skin so that it causes a depression or depressions in the skin, and applying a stimulating signal to the studs substantially as described and claimed herein. The method of the invention extends to the frequency, duration and current of the electrical stimulation applied to the studs.

The invention also extends to locating the studs by means of a stimulating device that is used to optimise the area to be treated prior to applying the studs.

Velcro attachments or polymeric straps allow the device to be attached in such a way that it can be reused; the polymeric straps additionally have the advantage that they can be sterilised for use by a different patient. If an adhesive is used to stick the support to a patient's skin, the adhesive surface will need to be protected by a plastics substrate between uses.

Each stud may have a substantially hemispherical or parabolic shape with a diameter of 3 to 12mm in diameter, and preferably between 6 and 8mm in diameter. In some applications smaller electrodes 4 to 6mm in diameter are to be preferred, for example to provide a higher density of electrodes. In areas where a more generalised relief is required, larger studs of diameter between 8 and 12mm may be preferable. As the studs are substantially hemispherical or parabolic in form their height (from their base to their apex) is equal approximately to their radius or optionally 1 to 2mm more.

The studs need to be capable of transferring an electrical stimulating signal to the patient's skin, and therefore in most cases will be metallic, often plated for appearance or protection. However, the ability to coat plastics with a metallic coating to produce an electrically-conducting surface allows the studs optionally to be made of a plastics material. Whilst the studs must have a non-penetrating, generally rounded surface that abuts the patient's skin, there is no restriction as to their shape, disposition, arrangement on a support, save as required to treat the affected are of a patient, be it large, small, elongated or otherwise, and the density of treatment called for by the physician or specialist.

For rectal, urological, gynaecological and other applications where the studs may be in contact with more delicate tissue, they may be of a shallower and more rounded shape. In such applications they may not need to indent the skin as much in order to make a satisfactory electrical contact. In all applications it may be helpful or necessary to apply a silicone gel or similar product to assist in producing a satisfactory electrical-conducting contact with the patient's skin. These studs may conveniently have a diameter of 8 to 10mm, but have a reduced height (base to apex) of 3 to 5mm. Plastics studs with a metallic coating may be preferred in this application, being potentially softer and having some flexibility.

The diameter of supporting washer or backing plate where required will generally be two or three times the diameter of the studs, say, 15 to 30mm, preferably 20 to 25mm, in diameter. It may equally be of a substantially elliptical, square, hexagonal or octagonal shape as may be dictated by the required application.

The studs may additionally have, or be formed integrally with, surrounding washers that enhance the degree of support and firmness by which the studs may be applied to a patient's skin. Alternatively, the surrounding washers may be formed of a plastics material and attached solidly to the studs.

The device advantageously comprises means for electrically connecting some or all of the studs as electrodes to a stimulating signal generator for producing a stimulating signal or series of pulses for the treatment of the pain by means of transcutaneous electrical stimulation. This electrical stimulation, either intermittently or continuously, combined with the pressure applied to the studs provides in most cases very successful relief of acute and chronic pain and the specified conditions.

The positioning of the stud electrodes may additionally be selected or adjusted by means of the patient's response to a stimulating device, or simply by carful manipulation of the device over the selected area until optimum relief is achieved.

In use the support, and thus the studs are kept in firm contact with the patient's skin, without penetrating it, either by such mechanical means such as an adhesive, or the straps or Velcro that hold it in place or due to the stretch of the fabric that it is made.

When the pressure is applied by means of the support the rounded tips of the studs are purposely designed to apply a specific pressure so as only to depress or indent the isolating outer surface layers of the epidermis so as to stimulate the receptors of the skin, though not through penetration.

When electrical stimulation is applied the combination of electrical stimulation and the firm pressure on the stud electrodes has been found in many cases to produce a significant relief of the pain that has been targeted, that may endure for hours, if not days. The electrical stimulation may be low frequency, e.g. 1 to 50Hz, or high frequency, e.g. 5 to 10kHz, depending on what works with the particular patient and their condition. At present frequencies of 2 to 10Hz are preferred in many applications.

The device may be provided with a connection or connections or a terminal for attachment to a stimulating unit having a power supply and a signal generator to produce a stimulating signal that can be varied and adjusted to suit the needs of the patient to be treated. Generally the parameters of the stimulating signal will be set by a physician or specialist so that the patient has no or only limited ability to alter the stimulating signal in amplitude or frequency.

As electronics and power sources improve and become smaller and cheaper, in a preferred embodiment the signal generator and the power source form part of the device or may be removably attached to it or arranged to clip onto a terminal that has been provided for a hard-wire connection. In such a case the device may conveniently incorporate a radio frequency transmitter so that the stimulating parameters can be set and modified either by using stimulating unit equipped with a suitable transmitter. Alternatively, the parameters can be set and controlled by an RE link with a computer, tablet or cellular phone using an appropriate application. Such external means for controlling the device by means of an RE link will be referred to herein in the specification and claims as external control means as herein defined'.

The stimulating parameters may be set by a physician or specialist who may allow S room for the patient to switch the device on and off, within permitted limits, and to make small adjustments to the frequency, pulse duration and amplitude as pro-set by the physician. In such an embodiment, the device is effectively self-contained and can be left in place without wires. It may even incorporate a timer so that it applies a stimulating signal at pre-arranged times to treat persistent pain.

Whilst the electrical stimulation is generally applied for a limited time, often between five and 20 minutes, by retaining the studs in place with the applied pressure has been found to enhance and prolong the relief. This may be particularly useful for injured athletes wishing to train or compete in spite of an injury. In such cases it may not be practical (or indeed even permitted) to apply the electrical stimulation during exercise, though a bandage with one or more studs that apply pressure to the skin, muscles and or nerves may be possible. Nevertheless, for some patients it may be necessary for the treatment to be longer, intermittent or even continuous or substantially continuous on a 24 hour basis.

The insulating support may comprise a flexible strip, band or patch and each stud preferably has a stiff surrounding backing plate or a washer several times, say, 2 or 3 to 5 times, the diameter of the stud of the electrode in order to better transmit the pressure firmly from the stud electrode to the skin of the patient.

In a preferred embodiment the stud array is mounted on an insulating support comprising a semi elasticated fabric having an adhesive surface on the side of the studs so that in use the insulating support can be stretched over the patient's skin in the area to be treated and held firmly in place by the adhesive so that the studs are held firmly against and exert pressure on the patient's skin. Such an adhesive elasticated strip may be cut to the desired length and stretched and stuck over a painful muscle, nerve or tendon, on the leg or arm, for example following an injury or surgery.

In specific cases, the device may be formed or constructed to fit a specific part of the anatomy, such as a glove for a hand, or a support for an ankle.

One specific form may be adapted specifically to treat rectal pain; this may require softer or flatter studs to avoid the device causing discomfort in itself.

Where the device is intended for re-use, for example where it is specifically formed to fit an arm, leg or joint and is more costly to manufacture, it may conveniently be held in place by means of one or more plastic or elastomeric straps, so that it can be washed, and sterilised if necessary.

In one embodiment of the invention the support comprises several perforated strips each of which has a number of studs arranged in a desired pattern. The support may be used either as a single patch having a relatively large number of stud electrodes, or it may be cut or torn into single or multiple strips as desired and optionally stretched to fit over a part of a patient's body. Studs may be chosen or activated to correspond with specific locations on a patient that can be identified by a practitioner by using a stimulating device. In this way a very effective treatment may be achieved without activating ineffective electrodes, thus prolonging the life of the power source.

Studs on adjacent strips may be operated in association with each other or independently.

The stud(s) may be placed appropriately for the injury.

In another form, the insulating support may advantageously incorporate an internal electrical conducting means arranged to make electrical contact with the desired electrodes on the support. This may be in the form of a conducting strip, band or web formed of an electrically conducting material. The stimulating electrodes may thus be selectively riveted through the insulating support in such a way that they make contact with the electrical conducting means. Alternatively, the insulating support may be provided with pre-formed holes adapted to receive the electrodes in such a way that they make electrical contact with the electric conducting means disposed within the insulating support.

An electrical reference or earthing signal may be applied to the patient's skin either through a conducting silicone patch, or by connecting one or more of the studs to the reference signal or by incorporating an earthing patch on the support itself for the reference signal.

In another embodiment selective bands of conductors within the insulating support are arranged to carry a stimulating signal and a reference signal so that stimulating electrodes are in electrical contact with a stimulating signal and reference electrodes are in contact with a reference signal.

In its simplest form the insulating support may comprise a pro-formed band, strip, belt or bracelet so dimensioned that it can be attached around a limb, wrist, ankle, head or torso of a patient in a way that the electrodes are brought into and maintained in firm contact with the patient's skin while an electrical stimulating signal is applied.

The electrodes (studs) can be incorporated in any design, shape or form required for specific applications. For example, the insulating support may be so configured as to fit closely around a part of a patient's anatomy where treatment is to be applied so that the electrodes are held and maintained in firm contact with the patient's skin. In fact, the stud electrodes can be incorporated in clothes, underwear, shoes, braces, attelles. Fabric, elasticated or plastic bands of different shapes, may be shaped and form an integral or replaceable element of the item. The studs may even be incorporated into bijuterie, e.g. for facial or cranial stimulation. Such may be suitable for covering, dissimulating or making the electrical stimulating device effective, though discrete and less evident to third parties.

The number, spacing and disposition of the studs may be arranged and adapted to the patient's pain profile.

Specifically the physician or specialist may select either the standard diameter studs (8 to 10mm in diameter), or the smaller studs (5 to 6mm in diameter) for more sensitive areas or where a higher density of studs is required. As mentioned above for rectal, urological, gynaecological applications the flatter studs may be chosen for reasons of comfort and practicality.

In another embodiment, the stud electrodes may be attached to the insulating support by means of a Velcro (Registered TM -3M Corp. Inc.) or similar backing which grabs' the support.

In one other variant of the invention the insulating support incorporating the desired stud array comprises a patch or liner, for example in the form of a mitten, that is arranged to be held firmly over a hand, or a sock that can be held over an ankle or an amputation by means of a semi-rigid or rigid formed shell permitting it be clipped or clamped around a part of a patient's anatomy that is to be treated.

In some instances it may be helpful to encase the support in a shell may comprising a casing provided with foam or fabric liner or sleeve in order to more comfortably adapt it to the patient's anatomy, and to provide the desired level of pressure on the electrodes. This may be particularly well adapted for treating an ankle injury, an amputation or a wrist or other limb injury or associated chronic pain.

Whilst a number of different applications have been alluded to, the invention may be used in various embodiments where a pre-formed insulating support with an array of electrodes may be adapted to fit the area to be treated and to the treat localised pain.

In another application the insulating support comprises a sleeve or suitably-shaped patch for treating rectal, urological, gynaecological pain.

One or more light-emitting diodes LEDs) may be included on the outer surface of the support. These are included in the electrical stimulating circuit so that they light up when a stimulating signal is applied to the circuit. Where several discrete circuits are present, supplying different studs or groups of studs, LED5 may be included in each circuit; if desired, differently coloured LEDs may be used.

The invention will now be described by way of example with reference to the accompanying diagrammatic drawings, in which: Figure 1A illustrates a device for treating the specified conditions comprises an adhesive support having a single stud that can be adapted in form and size to be attached to a patient; Figure 1 B shows the support in Figure 1A in cross section in use applying pressure to a hemispherical stud with an indentation in a patient's skin; Figure 1C shows the support in Figure 1A in cross section in use applying pressure to a rounded stud with an indentation in a patient's skin: Figure 2A is similar to Figure 1 A but shows a support having a plurality of studs; Figure 2B is similar to Figure 1B, and shows the support attached and applying pressure to studs with a hemispherical distal end applied to and making an indentation on a patient's skin; Figure 2C is a side view of a support having studs suitable for rectal, urological, gynaecological applications; Figure 2D is side view similar to Figure 2B of a support having rounded studs.

Figure 3 shows the contact side of a device in the form of multiple support strips that can either be used as a single support to treat an enlarged area; the support is dimensioned to be attached around a limb or neck of a patient, and held in place by Velcro Figure 4A shows the external side of a device in the form of multiple support strips that can either be used as a single support to treat an enlarged area, or torn or cut into single or multiple strips according to the area to be treated; the support is arranged to be adhesively attached to a patient; Figure 4B shows diagrammatically a LED arrangement that can be used with the support; and Figure 5A illustrates various ways that a device can be positioned to treat a patient; Figure 5B illustrates a support comprising a pair of bands attached round a patient's wrist.

Figures 1A and 1 B (and an alternative in Figure 1C) illustrate respectively a plan of the external surface and a centre cross-section of a device 10 in accordance with the invention having a single stud 12 mounted on a semi-elasticated adhesive support 14, for use in the treatment of the specified conditions. In Figure lB the stud 12 has a smooth, substantially hemispherical form for contact with a patient's skin 20, and in Figure 1C the stud has a rounded distal end where a lesser indentation is required or is necessary to achieve the desired indentation of the patient's skin. The stud 12 has a flat backing washer 16 flush with the exterior surface of the support 14 in order better to transfer pressure from the support to the stud 12.

In use, the support is stretched and stuck by means of its adhesive surface 18 to the patient's skin in the desired location so that the hemispherical stud is pressed against the patient's skin due to the adhesive grip of the support 14. (Note: in the drawings the adhesive surface of the support, and the stud(s), may not be shown as actually touching the skin, for clarity of illustration.) But in use the adhesive grips the skin -with no gap between the two -so that the studs are pressed firmly into the skin; similar interpretation should be made where other means of attachment are used.) In practice the depth (from its rounded distal surface to its back in line with the backing washer 16) of the stud 12 (as in the other applications described below) will be chosen according to the diameter of the studs, the application to be treated and the desired pressure on the studs against a patient's skin required to achieve the benefit of the electrical stimulation. For applications where a deeper indentation is required, for example on the abdomen of an obese patient, the depth of the studs may need to be increased or the studs prolonged. Improved electrical conductance can be achieved by using a conducting gel.

The stud 12 may be positioned for optimum effect using a stimulating signal applied to stimulating probe (not shown). The amplitude, frequency, pulse duration and length of each treatment will be determined by the patient's reaction to the initial stimulating signal and that applied in use to the stud 12.

The stud has an electrical connection 22 to a terminal or control unit 24. Where the device is hard-wired to an external stimulating unit, it is connected via the terminal 24.

Alternatively a signal generator and power source are provided at 24 and form part of the device or may be removably attached to it. The signal generator 24 incorporates a radio frequency transmitter so that the stimulating parameters can be pre-set by a physician or specialist external means as herein defined.

An earthing patch or reference electrode may be provided on the sticky surface 18 of the support, or as a separate silicone gel electrode attached nearby (not shown).

This to be understood in respect of all the examples of the invention shown and described herein with reference to the accompanying drawings. Where a plurality of electrodes is shown, some of the electrodes may be connected either to be used as reference electrodes or for the polarity to be alternated between electrodes, or for an external, suitably-dimensioned patch to be provided, or for a part of the adhesive surface of the support to comprise an earthing or reference electrode.

Generally the parameters of the stimulating signal will be set by a physician or specialist by hard wire or via an RE link so that the patient has no or only limited ability to alter the stimulating signal in amplitude or frequency. Where the patient is able to fine tune the stimulating signal this is achieved by means of an RE link to a cellular device, or by other external means as herein defined.

A timer may be incorporated so that the stimulation takes place at regular intervals.

The lack of hard wiring to the device greatly improves its acceptance and convenience for the patient. The power source may be battery powered, rechargeable, or fed by RE means.

Eigures 2A, 2B and 2D similarly show diagrammatically a device 10 comprising a plurality of electrically-conducting hemispherical studs 12 projecting from an insulating support 14 to which the studs are attached or inserted with a formed or attached backing washer 16 as described under Eigure 1 above.

As in Eigure 1 each stud 12 that is to be used for the electrical treatment is provided with an electrical conductor 22 linking it to a terminal or signal generator and power source at 24.

In use pressure is applied to the studs 12 in order to keep them in firm contact with the with the patient's skin; this in itself may produce significant relief. In order to enhance the relief, low, varied or high frequency electrical stimulation may be applied to the studs as detailed below. The combination of multiple electrical stimulation and firm pressure on the stud electrodes produces in many cases a significant relief of the pain that has been targeted, that may endure for hours, if not days.

Figure 2C is a diagrammatic side view of a support 14 having shallower studs 12 suitable for use in rectal, urological, gynaecological applications. The studs may be 8 to 10 mm in diameter, but only 3 or 4mm high (from base to apex) so as to minimise discomfort. Equally, the support may be specifically shaped and adapted to its purpose. It has a suitable adhesive coating at 18 for achieving suitable adhesion to the patient's skin and for the studs 12 to have adequate contact without damaging the tissue. This is an application where he studs may be made of a softer plastics material, coated with an electrically-conducting surface may be preferred over harder metallic studs.

Figure 3 shows the under-side surface of a devicelO similar to the one shown in Figure 2. In this Figure, four studs 12 are shown, though there may be any number as required, and the support 14 may be dimensioned such that the device may be attached, by means of Velcro patches at 30 and 30', to a limb or the neck of a patient. In this example, the support 12 is shown as forming one of three similar supports, formed as a single support. In use it may be employed as a single device to treat a painful area, such as a patient's lower back, or may be cut down or torn along the markings or perforations 32 to form a double or single support, as desired.

Where the support comprised 4 electrodes, and is three strips wide, it will typically measure 10 to 100 cm long, and each strip will be 2 or 3 cm wide. The reference numerals are those identifying similar items in Figures 1 and 2 and relate accordingly.

Figure 4A shows the outer surface of a multiple adhesive device 10. Figure 4B shows an LED arrangement as used to produce a light effect when a stud electrode receives a stimulating signal of either polarity.

Although the device in Figure 4A is provided with an adhesive surface on its underside from which the studs project, it is otherwise similar in dimensions and characteristics to the device shown in Figure 3. The two differences are that an LED 34 (or pair of LEDs in the case of an alternating polarity of the stimulating signal) is provided above one of the stud electrodes 12. Also an earthing or reference patch 36 is provided on the underside of the support 14 and electrically connected to the terminal or stimulating unit at 24. As the device in Figure 3, the device may be used as a single strip of the support, or cut or torn along the perforations 32 to provide a single or multiple strips.

Figures 5A and 5B illustrate figuratively how single or multiple strips of the support 12 S as described with reference to Figures 3 and 4 may be employed in practice on a patient.

In another embodiment the studs in the form of sticky patches or Velcro-backed patches can be selectively attached to the support 14, positioned as desired for the treatment. Positioning may be refined by using a stimulating probe to locate the nerve and muscle locations so that the patches with the stud electrodes may be positioned appropriately on the support. Such patches may be moved to adapt to the patient's response to treatment, or to accommodate a new patient.

In general, selective rows of studs on the insulating support are arranged to carry a stimulating signal and return path electrodes allow for a completion of the electrical circuit. If desired the signal to the stimulating and return electrodes may be reversed, either alternately or in sequence or in an arbitrary fashion. The device may be moved if desired in order to optimise treatment or extend the area of treatment.

Alternatively, the return path connection may be applied to the patient by means of a conducting silicone carbon patch (not shown): in view of the larger number of stimulating electrodes the conducting area of the patch may be significantly greater than that of each of the stimulating electrodes in order to avoid an excessive localised current that could cause discomfort.

Whilst a number of different applications have been alluded to, the invention may be used in various forms where a formed insulating support with an array of studs may be adapted to fit the area to be treated.

For example, the insulating support may be formed for treatment of a specific location. For example, the support may incorporate an electrode array in a suitable shape or sleeve for treating severe rectal distress.

In the device according to the invention the power supply may be arranged to apply a locating pulse to one or more of the stud electrodes in order accurately to locate the relevant nerve group in a patient in order to maximise the relief to the patient yet using the smallest possible current.

The tact that the studs are arranged to be applied externally for non-invasive use permits the device to be used and, to a certain extent, controlled by a patient, although the initial set-up of the device will generally be performed by a medical practitioner or specialist. The very low current which has been found to be effective allows the device to be manipulated sately by older people -the most trequent sufterers trom chronic pain -or even by children or people who are handicapped, without endangering them. Alternatively, the reliet provided by the pressure of the studs may be sufficient to relieve the pain or discomfort, so that no electrical stimulation is required, or is required only infrequently.

The device is most etfective when the stimulating electrodes comprise substantially hemispherical contacts which are dimensioned to project in such a way that they can be applied to an atfected area with sutticient pressure that they produce small indentations in the skin. The electrodes are preterably mounted on a non-conducting, semi-rigid support or supports. The firm pressure, sutticient to produce small indentations in the skin, together with the stimulating signal contributes significantly to the eftective treatment of the pain.

In a preterred torm of the invention a number ot stimulating electrodes is used to treat an extended area. There may be between 2 and 24, though generally not more than 16, stimulating electrodes whose centres are between 30 and 150mm apart according to the application. In practical terms there are ideally 4 to 6 stimulating electrodes with an enclosed area of 150 to 200 cm2. For treatment ot the back or spine, however, typically 16 electrodes may be required, arranged in 8 pairs and covering up to 1,000cm2.

Where narrower studs (4 to 6mm in diameter) are used narrower spacing may be used, from 10 to 15mm apart.

Each stud may have a substantially hemispherical or parabolic shape with a diameter of 3 to 12mm in diameter, and preferably between 6 and 8mm in diameter. In some applications smaller electrodes 4 to 6mm in diameter are to be preferred, for example to provide a higher density of electrodes or for more delicate tissue. In areas where a more generalised relief is required, larger studs of diameter between 8 and 12mm may be preferable.

The diameter of supporting washer or backing plate will generally be two or three times the diameter of the studs, say, 15 to 30mm, preferably 20 to 25mm, in diameter. It may equally be of a substantially elliptical, square, hexagonal or octagonal shape as may be dictated by the required application.

A stimulating signal may be applied to different electrodes or pairs or selected groups of electrodes alternately, sequentially or in rotation to improve the level of relief to the patient, and the power supply is conveniently arranged to offer this feature. This also has the advantage of reducing the current density at the reference electrode(s) and the overall required power output of the power supply.

The stimulating signal applied to each electrode may be applied sequentially with such a shod delay between each electrode that it is indiscernible by the patient that not all the electrodes are activated simultaneously.

In general the stimulating electrodes will be anodes (+) with the return electrode being the cathode (-). However, some patients find that inverting the polarity produces greater relief and thus the polarity can be selected by the specialist accordingly.

The energy required for the treatment may depend on the size of the nerves (large, heavily myelinated A a motor fibres at one extreme versus smaller unmyelinated C fibres at the other). Thus the energy delivered E (energy in nC) = I (current in mA) x (duration in ys). In a typical example, a pulse may last from 0.O5ms to lms and the applied current may be from 0.5mA to 6OmA. In practice the highest currents would not be used with the longest pulse widths, so that the power per pulse would not be likely to exceed 50mG and would be more likely to be in the order of 15 to 25mG or less for a tender part of the body.

In order to obtain the necessary transcutaneous current a relatively high voltage -up to 85V, though more traditionally 65V -may be required. The pressure that can be applied by the stimulating electrodes (and by the other, reference, electrode) to the skin allows the voltage to be reduced because of the lower resistance, making burning less likely. The provision of rounded ends of the electrodes also acts to distribute the current more accurately and evenly than would be achieved by a traditional silicon carbon electrode. A gel may be used to enhance the conductivity between the reference electrode and the skin.

The frequency may be effective in the range of stimulation 1 -50Hz, and preferably between 2 and 10 Hz or up to 50Hz, but not usually in the 50 -150 Hz range. For other patients, higher frequencies up to 5kHz or 10kHz may be preferred. In other applications it may be most effective to vary the frequency over the treatment according to the site, the patient and the required treatment.

The device may thus be set to provide a specific current at each stimulating electrode of between 0.2mA and 6OmA. Optimal results appear to be achieved when the applied current to each electrode is between 2 and 1 OmA or even 2OmA. The current combined with the pulse width determines the level of energy applied. The pulse width may be from SOpS to 1 mS. The penetration of the signal increases with the pulse width while the applied current may be increased at shorter pulse widths.

The current is set by the practitioner on a judgment basis, the patient's skin and the part of the body to be treated with an objective to use the lowest current consistent with achieving the desired relief and without causing discomfort. Clearly more delicate parts of the body, for example around the eyes, or more fragile skin will require the current and power to be limited accordingly.

Once the stimulating electrodes have been accurately positioned the current can be reduced in most cases and the frequency can be adjusted to achieve the optimum level of relief. Accurate location of the electrodes thus reduces the discomfort to the patient and the risk of burning. It also prolongs battery life for a portable device.

For maximum effectiveness the electrodes are carefully positioned using the device in its stimulator-and-location mode prior to treatment. Thus, the device is first used to position the treatment electrodes prior to fine-tuning the treatment current and frequency. The power supply may then be adjusted and used to provide the desired electrical output to the electrodes for the treatment.

As it may not be necessary to carry out the location procedure on each occasion, either a separate nerve stimulation function on the device may be used by the specialist practitioner who prescribes the treatment or a separate locating stimulator may be used. In normal use the location function is switched off so that the patient is not confused. The treatment parameters equally may be pre-set or pre-limited to prevent the patient from harming himself by mistake.

The diameter of the contacts of the studs will depend on the muscle or nerve type to be treated. As a general rule the height (from base to apex) of the studs will be equal to their radius or 1 to 2mm longer. They may be between 4 and 12mm long or in some cases up to 20mm for treatment of the abdomen of obese patients, but generally 4 to 6 or 8 mm. They are mounted on the inner side (in use) of a semi-rigid support coated with a suitable adhesive, such as the zinc oxide used on sticky plasters. If it is intended to reuse the support and the studs, a re-usable adhesive may be used, provided that the adhesive-coated side is attached to a plastic sheet between uses.

Alternatively, as described it may be held in place by means of a belt or strap, or secured by a Velcro (® 3M Corp. Inc.) clasp.

External multiple neurostimulation in accordance with the invention results in improved relief of the specified conditions, an improvement in peripheral circulation, improved mobility and improved sensory perception. It has the great advantage that it can be applied by the patient when and as often as with little or no adverse effects.

As no surgical procedure is required, treatment can easily be modified or stopped if it fails to produce the desired relief or if it causes an unwelcome response.