WO2010033055A1

WO2010033055A1 - A system for applying controlled selective vibration stimuli to the hand

Info

Publication number: WO2010033055A1
Application number: PCT/SE2008/000515
Authority: WO
Inventors: Göran LUNDBORG
Original assignee: Handmedic Hb
Priority date: 2008-09-17
Filing date: 2008-09-17
Publication date: 2010-03-25

Abstract

An equipment for inducing controlled vibratory stimulation to individual fingers or other parts of a hand comprising vibration exciters adapted to said parts of the hand either directly or incorporated in a glove, fed with signals from an external signal source preprogrammed for delivery of defined vibration stimuli to said fingers or parts of the hand. Pulses of vibrations are delivered to individual fingers according to a pre-programmed pattern so that the vibration stimuli, applied consecutively to individual fingers, are separated spatially and in time with possibilities for variations in frequency, intensity, length of vibration pulses and intermission between vibration pulses. The vibration stimuli can be delivered by DC-electric motors with eccentric weights applied on the axis, electro- active polymers, pietzo-electric membranes, loudspeakers or any other system which can induce appropriate vibratory stimuli. The equipment is constructed for treatment of focal dystonia, writer's cramp, dys-coordination or chronic pain, aiming at a normalisation of reorganisational changes in brain cortex which may be associated with such conditions.

Description

A system for applying controlled selective vibration stimuli to the hand Background of the invention

This invention relates to a system for inducing controlled vibratory stimulation of individual fingers or other parts of a hand. The aim is to offer a new treatment option for patients suffering from focal dystonia, writer's cramp, dyscoordination or/and pain. The principle may be useful also in the rehabilitation process after various types of hand/arm injuries.

The biological basis for the invention is the central representation of the hand in somatosensory brain cortex receiving sensory impulses from the periphery. A prerequisite for well coordinated fine motor functions in the hand is a good sensory feedback and a well organised and physiologically intact somatosensory cortex [I]. Electrical signals, elicited by touching the hand, are transferred via nervous pathways primarily to contralateral somatosensory brain cortex, here constituting a neural map of the hand, also called the cortical hand map. In primates, exact hand and finger representations have been meticulous outlined by direct recordings from the cortical surface [2-5], and in humans a corresponding cortical mapping of the hand has been identified by use of various brain imaging techniques such as magneto-encephalography (MEG) and functional magnetic resonance imaging (fMRI) [5-8]. In the cortical hand map the individual fingers are well separated by sharp boarders, the thumb being located inferiorly in relation to the fifth finger.

The various subcomponents of the cortical hand map is kept well-defined and topographically separated as a result of the physiological sensory inflow from a normally functioning hand implying non-synchronous sensory impulses from spatially separated parts of the hand to brain cortex. However, there are various situations when this strict organisation of the cortical hand map is deteriorated and changed to a more diffuse and randomised pattern. The result may be impaired sensory/motor function, dyscoordination and/or pain.

Focal dystonia

The cortical hand representation may be modified and distorted by non-physiological use of the hand. Such events may be seen, for instance among musicians suffering from functional dystonia, which is a incapacity to control and regulate individual finger movements. In such situations, the cortical hand map is distorted and changed into a disorganised pattern [9-14]. The physiological bases is repetitive, monotonous use of the hand with non-phsysiological tactile stimulation over extended periods. In such situations the normally well separated cortical projectional sites of individual fingers are fused so that the normally well organised cortical hand representation with separated bands for individual fingers is totally changed into a mosaic-like disbursed pattern. As a result of an impaired sensory processing in somatosensory cortex the motor cortex is also influenced, leading to impaired ability to control fine movements of the hand.

Focal dystonia is very difficult to treat, but according to current concepts the aim of the rehabilitation should focus on reversal of the reorganisational changes in the cortical hand map. This is usually done in intense and tedious rehabilitation programs where tactile stimuli are applied to spatially separated parts of the hand in a non-synchronous way. Another approach is to immobilise parts of the hand in a splint to allow movement in only one or few fingers [9, 10, 12, 15, 16]. The aim of the present invention is to offer a new possibility for organising the cortical hand map by stimulating individual spatially separated fingers consecutively according to a predetermined program using an electronic vibratory device.

Another characteristic symptom, emanating from overuse or non-physiological use of a hand is writer 's cramp characterised by fatigue, cramps and inability to control individual fingers. According to current concepts also writer's cramp is associated with a functional reorganisation of the cortical hand map into a disorganised, mosaic-like and disbursed pattern.

Pain

Chronic pain is a problem of enormous complexity, which can be based on structural and functional changes in the peripheral nerves, spinal cord and brain. Nociceptive, painful peripheral stimuli may activate pain fibres, and via complicated relay systems in the spinal cord, brain stem and brain such stimuli reach higher cortical centres resulting in pain perception. A special type of pain is neuropathic pain, based upon an injury or a lesion in the nervous system itself. After amputation of a body part phantom pain may occur, resulting in severe suffering and impaired life quality. Such phantom pain has been referred to the functional reorganisations which occur in somatosensory brain cortex following amputation injury: arrest of sensory inflow from the periphery induces severe reorganisational changes in the cortical hand map. It is well known that phantom limb pain occurs to an extent that correlates well with the extent of cortical reorganisation which follows the injury [17-20]. Theoretically, a normalisation of the disorganised cortical hand map would then help to reduce the pain, a fact which has been adopted in the s k mirror training as described by Ramachandran [21, 22]. The current invention is designed to offer an alternate way to normalise the disorganised cortical hand map by applying consecutive, non-synchronous vibratory stimuli to individual spatially separated fingers according to a predefined program.

Vibratory stimulation of fingers

Vibrations are induced to individual fingers by multiple vibration exciters, either incorporated in a glove or individually applied onto separate fingers. In the present invention vibration is induced by small electric DC-motors with a weight attached in an eccentric way to the axis, but other systems for inducing vibration such as loudspeakers, electro-active polymers, pietzo-electric membranes etc can also be used. The vibration exciters are fed with signals from an external signal source, containing a memory with an excitation pattern according to a program which has been created on a pc. The signal source can be small sized and applied to the body close to the vibration exciters. Pulses of vibrations are delivered to individual fingers according to the pre-programmed pattern so that the vibration stimuli, applied consecutively to individual fingers, are separated spatially and in time and with variations in frequency, intensity, pulse length, and intermissions between pulses. The total length of one sequence containing a defined number of pulses can be controlled and varied.

Summary of invention

The invention constitutes a system aiming at reversal of functional reorganisational changes in the cortical hand map associated with focal dystonia, writer's cramp, dyscoordination or pain. Such a normalisation of the cortical hand map with • reestablishment of normal functional boarders between individual finger representations can be induced by a training program based on stimulation of individual spatially separated fingers with pre-programmed vibratory stimuli, occurring non-synchronously. In the current invention vibratory stimuli are applied to fingers according to a predefined pattern in an order and of a magnitude which is controlled by a regulatory signal source. The thumb, index finger, long finger, ring finger and little finger can in this way be stimulated individually and consecutively one at a time so that the vibration stimuli which are applied consecutively to individual fingers can be separated spatially and in time and with variations in frequency, intensity, pulse length and intermissions between pulses. In the present invention vibration is induced by small electric DC motors with a weight attached in an eccentric way to the axis, but other systems for inducing vibration, electro-active polymers, pietzo-electric membranes, loudspeakers etc can also be used. The individual motors can be incorporated in a glove or they can be attached individually directly to individual fingers. Each motor is connected to a signal source, which can be adapted to the body close to the hand. The stimulation pattern is created on a pc, and the pattern is transferred and loaded in a memory card in the signal source.

Brief description of drawings Fig. 1 is a conceptual view of the stimulatory device (1), as attached to individual fingers and connected to a signal source (2) via connecting cables (3). The vibratory exciters can be incorporated in a glove, in a hood applied externally to the glove or can be applied directly to individual fingers (Figure 2). The system allows for vibratory stimulus of individual fingers which can be separated spatially and in time on bases on a predefined pattern generated by the signal source.

Fig. 2 is a magnified view of an individual vibratory stimulator here based on a electric DC-motor with a weight, attached in an eccentric position to the axis.

Detailed description of the invention

The aim of the invention is to apply vibratory stimuli to separate fingers in a way which will reverse and normalise the distorted and reorganised cortical hand map which is seen in associated with e.g. focal dystonia, writer's cramp, dyscoordination or chronic pain. The stimuli, here delivered by vibrating electric DC-motors, can be applied in many various ways. The character of stimuli is regulated by a signal source which enables variations with regard to frequency, stimulation intensity, length of stimulation period for each finger, length of time period between stimulation of individual fingers as well as spatial consecutive order of stimulation.

In the glabrous skin of the human finger there are several types of mechanoreceptors responding to vibration, pressure and stretching [23-26]. They may be fast adapting (FA) or slowly adapting (SA). Among fast adapting receptors, responding to vibration, the Meissner corpuscles are situated superficially in the dermal papillae. Meissner's corpuscles have small receptive fields and respond mainly to vibrations up to 50 Hz. Another type of fast adapting receptor is represented by the Pacinian corpuscles, situated in subcutaneous layers. These receptors have large receptor fields and respond primarily to high frequencies, above 50 Hz. A type of slowly adapting (SA) receptors are the Merkel end organs normally found at the centre of the papillary ridge, responding mainly to static pressure. The Merkel end organs transmit compressing strain from the skin to the sensory nerve endings, responding especially to indentations that are produced when edge cuts through the receptive field. Ruffini receptors, another type of slowly adapting (SA) receptors, situated in the deep dermal layers, respond mainly to stretching and deformation.

The system should make possible stimulation of individual fingers at any type of chosen frequency and intensity, depending on the type of stimulation exciter and control signal. The system should also allow for any type of stimulation pattern. For instance each finger could be stimulated in a spatially sequential way one at a time, starting from the thumb or from the little finger. The stimulation program could also be adjusted to induce a randomised stimulation of the fingers, one at the time, or according to a pre-programmed pattern. The system should also allow for stimulation of all fingers simultaneously.

Various types of vibratory devices can be used depending on the requirements and frequency chosen. A simple type of vibrator is electric DC-motor with a weight attached in an eccentric way on the axis, but other types of vibrators such as electro-active polymers, pietzo-electric elements or vibrating membranes according to the loudspeakers principle. The vibrating stimulator can be incorporated in a glove or can also be attached directly onto the finger. The vibratory element can also be attached to a dorsal aspect of the hand.

References

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Claims

Patent claims

1. A system designed to deliver controlled vibratory stimuli to fingers or other parts of the hand by one or several vibration exciters connected to a signal source, allowing any type of spatial sequence order in vibratory application to individual fingers, making possible a strictly pre-programmed stimulation pattern or randomised pattern generated by chance as well as any type of time dynamic pattern and sequential order in application of vibration pulses and with regard to frequency, intensity, length of vibration pulses and length of intermission periods in between vibration pulses.

2. A system according to claim 1 characterised by vibration exciters being applied to individual fingers or other parts of a hand.

3. A system according to claim 1 allowing the vibratory devices to be incorporated in a glove, or applied directly to individual fingers or other parts of the hand.

4. A system according to claim 1 allowing vibratory stimulation of all fingers or other parts of the hand simultaneously.