WO2008116234A1

WO2008116234A1 - Device for re-learning sensitivity

Info

Publication number: WO2008116234A1
Application number: PCT/AT2007/000143
Authority: WO
Inventors: Robert Schmidhammer; Heinz Redl
Original assignee: Robert Schmidhammer; Heinz Redl
Priority date: 2007-03-26
Filing date: 2007-03-26
Publication date: 2008-10-02

Abstract

Described is a device for re-learning sensitivity comprising: one or more sensors, said sensors being sensitive to contact and pressure; an audio signal producing unit and a visual signal producing unit, said audio signal producing unit and said visual signal producing unit being designed for receiving contact and pressure signals from the sensor (s) and for producing audio signals and visual signals in correlation to said contact and pressure signals.

Description

Device for re-learning sensitivity

The present invention relates to a device for re-learning sensitivity.

Neuroscience research within the last decade has shown that neural plasticity is a ubiquitous mechanism, by which the brain represents and encodes its dynamic sensory world.

The brain is a complex neural network which continuously remodels itself as a result of changes in sensory input. Plasticity can generally be defined as the capability of being moulded. Such synaptic reorganizing changes may be activity-dependent, based on alterations in activity and tactile experience, or a result of de-afferentiation. Recent brain imaging techniques have demonstrated that functional synaptic reorganisation in brain cortex can commence within seconds and continue for a very long time. For instance, extensive use of the hand may result in enlargement of the corresponding projectional areas in the brain. Nerve transection and repair leads to a very significant functional reorganisation in the corresponding cortical areas as a result of de-afferentiation in a first stage and misdirection of outgrowing axons and aberrant innervation of peripheral skin area in a second stage.

Plasticity can be induced by changes in activity levels transmitted from peripheral nerves to the cortex. It appears that plasticity processes adapt in accordance with changes in sensitivity.

The process of plastic reorganization is a system-wide phenomenon involving both cortical and subcortical representations and starts immediately after nerve injury or disease. E.g., it is well known that hand function to a large extent is dependent on this sensory feedback system and that a hand without sensibility is a hand without function. This demonstrates the strong relationship between sensory input to the brain and processed signals from the brain back to the organs, e.g. muscles or sensory o __

organs of the skin.

Another example showing the importance of this sensory feedback system is the sensibility of the human feet, especially the sole region. It is an important tool for stable walking on a bumpy base. With sensibility lost in this region on both extremities, it is nearly impossible to move along in nature.

There are many situations where lack of sensibility constitutes a major problem for the function of the body region affected and improvement of sensory recovery would be of great importance.

1) Nerve injuries:

Severe transection or crush injuries in the arm or hand usually include lesions of one or several nerve trunks. For instance_r transection of the median nerve at the forearm region results in total sensory loss within the major part of the hand. Such an injury results in major disability since hand function is very much impaired due to the sensory loss. Following surgical repair of the nerve, axon sprouts grow into the distal nerve stump, advancing distally very slowly. Misorientation of axons and incomplete re-innervation of sensory organs often lead to a hand being permanently impaired. After repair of nerve trunks at wrist level, about six months are required to regain useful sensory recovery in the hand. During these months, when there is a complete sensory loss of the hand, the patient has great difficulties in using the hand since there is no sensory feedback to the brain. Cortical and subcortical neuronal networks will change immediately after injury, becoming re-modelled in a bad fashion when axons of the impaired nerves advance distally to re-innervate their target organs. Cerebral plasticity processes will change the networking of neurons.

2) Neurological diseases:

A large number of neurological diseases, e.g., polyneuropathies result in impaired sensibility or total sensory loss function, especially in the hand. 3) Amputations in the upper and lower extremity resulting in phantom sensation or phantom pain:

Loss of sensibility due to amputation frequently results in phantom sensations or even in phantom pain. This is mainly due to the de-afferentiation of the corresponding brain areas .

4) Stroke:

Impaired sensibility can be a problem also in stroke.

In US 6,589,287 a device for replacing vibrotactile sensory stimuli with acoustic stimuli is disclosed. This device is used for creating an "artificial sensitivity" in patients with absent, lost or impaired sensibility in a hand prosthesis, hand, finger or other body parts. The fingers of the patient are placed on microphones which pick up vibrational sounds from the finger tips when the finger tips touch or scratch the surface, on which the microphone sensors are placed. Any vibrational sound is then amplified so that the patient receives the sound as a substitutional sense replacing the lost sensibility sense. This device is therefore used for substituting of the sensibility sense with the acoustic sense.

Such a device is, however, not suitable for re-learning sensory action, e.g. after nerve repair or neurological diseases. Moreover, the devices according to the prior art do not allow the patient to distinguish between the mere "contact" of the body part to a given surface and the active pressing or other action of the body part to the sensors. Moreover, the devices according to the prior art are not adapted or adaptable to the specific body parts for which a lost or impaired sensibility should be re-learned.

Therefore, the present invention relates to a device for re- learning sensitivity, comprising

- one or more sensors, said sensors being sensitive to contact and pressure,

- an audio signal producing unit and

- a visual signal producing unit, said audio signal producing unit and said visual signal producing unit being designed for receiving contact and pressure signals from the sensor (s) and for producing audio signals and visual signals in correlation with said contact and pressure signals.

The device according to the present invention is optimally adapted for re-learning sensory action, especially after nerve repair or neurological diseases. The device according to the present invention distinguishes between the contact of the body part to the sensor and the degree of pressing (or any other action of the patient's body part) the sensor. The device according to the present invention can be ergonomically adapted to the body part to be trained, e.g. the hand, foot, arm, leg or artificial hands, feet, etc.

Preferably, the sensors are attached on a surface preshaped in the ergonomically optimal manner. According to a preferred embodiment, the sensors are attached to^" a soft and mouldable material. Any surface or form needed can be shaped from the soft and mouldable material which is specifically suitable to the individual patient. It is also possible to quickly switch the device from a "left hand" to a ^λλright hand" device (by re-moulding) or even to quickly switch from a hand-measuring device (hand-re-learning device) to a device suitable for measuring (or re-learning) feet sensibility. The soft and mouldable material according to the present invention can have a memory effect or not. For example, the product "Rolian Knetmasse" (Orthofit (AT) ) is specifically suitable.

Loss of sensibility in the upper or lower extremity or other body parts results in a severe hindrance after injury or in disease. Sensory re-learning methods and basics on cortical reorganization after peripheral nerve lesion are well documented. The present invention refers to the principle of virtual sensibility by substituting of senses in a three dimensional way.

The sensors according to the present invention are a combination of touch and pressure sensitive sensors (e.g. for touch 1 QMat- rix devices are digital charge-transfer (QT) ICs designed to - - detect touch using a scanned, passive matrix of electrode sets to achieve a large number of touch keys driven by a single chip and for pressure a standard transducer > 0.1 g sensitivity, for example Quantum QPROX.COM, QDMlIO, etc.).

Preferably, the audio signal producing unit and the visual-signal producing unit are combined in a single audio and visual signal producing unit in the device according to the present invention. At least one of the audio signal producing unit and the visual signal producing unit can be combined with the sensor (s) so that the signals can immediately be generated at the place where the measurement takes place, so that the signal can easily be correlated by the patient to the local action of the body part with lost or reduced sensitivity. The sensors and the audio signal producing unit and the visual signal producing unit can be connected to other parts of the device with cables or with radio signals (or other non-cable data transfer tools, such as infrared, blue-ray, etc.) for allowing signal/data transfer and/or energy supply.

A preferred field of action of the present device is re-learning sensitivity of fingers or hands or toes or feet. Therefore, the soft and mouldable material comprising one or more sensors is preferably designed for receiving a human hand. For such a device it is advantageous if the soft and mouldable material comprises 5 sensors for 5 finger tips of said human hand. In action, each of the patient's fingers on one hand is placed on one sensor and each of the fingers can then be trained independently. Such a device can also be used for diagnosing specific losses or disabilities in each of the patient's fingers and for monitoring the clinical development of such a state.

The audio-signal producing unit preferably creates a sound which makes the patient feel comfortable or does at least not make the patient anxious or frightened or does not otherwise interfere with contact/pressure measurement on the sensors. Preferably, the audio-signal producing unit comprises an electronic impedance-device controlled by a MIDI-Sequencer . Such sequencers can be used to create suitable sounds, also taking a patient's individual requirements and needs into account. The visual-signal producing unit can be designed very simply (onset of an optical signal, such as a light), e.g. so as to comprise light-emitting diodes (LEDs) . Preferably, the LEDs can be placed at the sensors (or close to the sensors) so that the patient can associate the active LED (as a signal for successful pressure over a given threshold at a specific sensor) to the limb (e.g. the finger) which has created the pressure signal. Even more preferred, the device has at least two different LEDs (in two different colours or light intensity, pattern) ; one for the "contact" signal and one other for the "pressure" signal.

On the other hand, the visual signal producing unit may comprise more sophisticated instruments, for example a monitor, preferably a flat screen monitor. These signals can be produced by computer animation, for example by displaying the body part of interest onto which the device according to the present invention is applied, preferably correlating the contact/pressure signal with the display of the body part on the monitor.

In order to show the pressure signal to the patient in a way allowing the patient to immediately associate the pressure signal to the body part of interest (e.g. a given finger), it can be advantageous to place the visual signal producing unit into the sensor (being then integrated into the sensor) or to place it in (close) vicinity to the sensor. The maximum distance between the sensor and the visual-signal producing unit should be the maximum distance which still allows the association of the signal to the body part tested (e.g. the finger). If the visual-signal producing unit comprises, e.g. an LED, the LED should be placed close to the finger so as to allow to distinguish between a signal produced by one finger and the signal produced by the neighbor finger.

One of the major advantages of the present invention is that the signals created by the device for sense substitution are detectable by the patient in a three-dimensional (3D) manner. Minimal touch at the affected (loss of sensibility) body part can be transformed into 3D-detectable acoustic and/or visual signals, especially at (or close to) the site of lost sensation. These audio-visual signals produced by the device according to the present invention make even minimal touch and change of pressure perceptible.

The present device for enhanced sensory re-learning produces 3D- detectable audio-visual signals for protection of corresponding cerebral sensory processing areas and the augmentation of cognitive memory (visual and acoustic sensory memory) and cognitive function. This results in functional improvement of the affected body region due to an improvement of cerebral plasticity processes. The use of the device according to the present invention should be started as soon as possible after nerve repair or in disease to protect sensory processing regions of the central nervous system and to improve cerebral plasticity processes.

The device according to the present invention creates virtual sensibility by the production of 3D detectable audio-visual signals due to minimal touch at the affected site, thus protecting sensory cerebral areas and improving cerebral plasticity processes. The present invention relates to the principle of virtual sensibility by sense substitution in a three-dimensional way. Therefore, lost sensibility due to nerve injuries or any other type of lesion or illness, which results in sensory loss or sensory impairment in the hand, parts of the hand, the foot or some other body part is substituted in a three-dimensional manner at the affected site (lost sensibility) , using the device according to the present invention. By the use of this device, the patient can "feel" due to 3D-detectable audio-visual signals and can utilize the hearing and visual sense to register and identify a surface which is touched slightly. In a similar way the patient can be made sensitive to changes in pressure.

Virtual sensibility is a principle where lost or impaired sensibility is replaced by an alternative system for sensory feedback. Virtual sensibility is created according to the present invention by the use of the aforementioned device producing 3D- detectable audio-visual signals. The goal of the invention to produce 3D-detectable audio-visual signals is achieved by: 1) Detection of a sensory stimuli, especially minimal touch at the site of sensory lacking, due to differentiation between a mere "contact" signal and a signal created by an active pressure by the patient;

2) Production of audio-visual signals resulting from such a stimuli (preferably this stimulus is created at the site where nothing is felt) which are detectable by hearing and vision, thus being processed three-dimensionally by two eyes and two ears.

3) Change of audio-visual signals due to change of pressure resulting from such a stimuli which are detectable by hearing and vision.

4) Change of audio-visual signals when different body parts, e.g. thumb, index and middle finger, can be differentiated.

5) The sounds of the signals have a pleasant type, avoiding fleeing reflexes or dysesthesia.

Therefore, the present invention also refers to a method for measuring contact and pressure at a sensor using the device according to the present invention, wherein a patient contacts the sensor of the device, whereby the device creates a visual and/or an acoustic signal (contact signal) ; then allowing the patient to increase the pressure onto the sensor; if the pressure onto the sensor increases over a predetermined minimal pressure level, the device creates a (further) visual and/or (preferably) a further acoustic signal (pressure signal) which is different from the contact signal.

Preferably, the contact without pressure touch (= contact only (= minimal touch) ) is the touch at the sensor without any "pressure" from the patient. The "pressure" signal is the signal produced by active pressing with, e.g., a finger. The pressure signal can, e.g. for fingers, be adjusted to be between 5 and 100 g, especially between 10 and 50 g, e.g. at 10 g, 20 g, 50 g or 100 g.

For example, the contact signal can be a LED with one coulor and a specific sound signal and the pressure signal can be the activation of an LED, preferably combined with a change in sound signal (e.g. silence or a different tone height, a different sound, a different tempo or rhythm or a combination of these sound effects). The contact signal can also be a visual signal _ _

(without sound) and the pressure signal a sound, preferably combined with a change in visual signal (e.g. inactivation of the LED, activation of a second LED with a different colour (and optionally inactivation of the "contact" LED) ) . The present device therefore is only transmitting changes in pressure onto the sensors, but not movements on the sensors.

As mentioned above, it is preferred if the signals are created close to the body part of interest, i.e. the body part affected by lost or impaired sensitivity. Therefore, it is preferred that the visual and/or acoustic signal is created at the sensor or within a short distance to the sensor.

Preferably, the visual contact signal differs from the visual pressure signal in colour, brightness and/or flashing pattern. It is further preferred that the audio contact signal differs from the audio pressure signal in tone height, sound and/or rhythm.

It may further be preferred that the visual or audio signal is different for different sensors. This is especially the case where sensitivity in a patient's hand has to be improved or measured. This is preferably done by measuring each of the fingers independently, at least thumb, index and middle finger. Therefore, according to a preferred embodiment of the present invention, the patient contacts five sensors of the device with the five fingers on one hand. Preferably, each of the visual and/or the acoustic signal of the five sensors is different from each other. In this embodiment it is specifically preferred to create the visual and/or the acoustic signal of the five sensors at the sensor or within a short distance to the finger on the sensor.

For all embodiments described herein it is specifically preferred that the device according to the present invention creates a visual contact signal, preferably combined with an acoustic contact signal and a visual pressure signal (being, of course, different from the contact signal) , preferably combined with an acoustic pressure signal. In an even more preferred embodiment, more than one pressure signal is produced, correlating to different levels of pressure. This allows measuring (and "feeling" by the audio-visual signal of) different pressures, depending on the patient's ability to use the body part being affected by the loss or reduction of sensibility. For example, two or three different "pressure" signals can be provided, each correlating to different pressure thresholds or continuous change. For example, the signal for the highest pressure level can be at a pressure level possible (or "normal") for a healthy person without reduced sensitivity (e.g. about 5 kg). With this embodiment of the invention, the course of the re-learning process can be monitored in an even more precise way, showing the improvements of the sensitivity in an even more detailed manner. The pressure signal can also be monitored by four or more "pressure" levels or even by a continuously responding signal (for example a continuous rise in sound volume or tone height upon continuous increase of pressure; i.e. a given pressure corresponds to a given sound volume or tone height; or a given pressure corresponds to a given colour or (colour or light) intensity) .

The present invention is specifically used for patients suffering from a loss or reduction of sensitivity of a specific body part, especially in the hand or fingers. The invention is preferably used for patients suffering from nerve injuries or neurological diseases, amputation patients (suffering from phantom sensations or phantom pains) or stroke patients. Such patients can be diagnosed, monitored and trained with the device according to the present invention.

The invention is further described by the following example and the figure, yet without being restricted thereto.

Fig. 1 shows the device according to the present invention adapted to re-learning sensitivity after nerve repair/disease by a "3D Virtual Sensibility Device" ("VSD") with 5 sensors with LED signals for each of the patient's five fingers on one hand. The sound is created by an audio-signal creating unit in vicinity of the patient's hand.

Example: A device according to the present invention with specifically preferred features for hands was designed (see Fig. 1) . This device is referred to as ^λΛ3D Virtual Sensibility Device" ("VSD") . The VSD allows enhanced sensory re-learning after nerve repair/disease by 3D detectable audio-visual signals .

The VSD for the hand has five sensors for each finger tip of the hand. The sensors are stacked on a soft and mouldable material that does not harden according to the anatomical and postoperative situation of the patient's hand or are connected directly at the patent's fingers. The sensor is imperative to be touched by the patient. The sensors are connected to an amplifier unit that produces an audio signal just in front of the patient's hand. Additionally, a visual signal is produced at the sensor changing colour when pressure of the patient's finger tip to the sensor changes. The change of pressure is accompanied by a change of the sound. The principle of three-dimensional detectable audiovisual signals is to be processed in the brain after detection by both eyes and both ears. The important third dimension is created by the fact of distance to two different sensing organs on the right and left side of the body. Additionally, it is important that visual neurons of the brain, which perform integration work of what is seen to corresponding brain regions, have the possibility to percept signals at the site of no or reduced sensibility. In a similar way the audio processing areas should be able to work up these signals, thus stimulating de-afferenti- ated sensory processing brain regions and augment cognitive memory (visual and acoustic sensory memory) and cognitive function. This results in functional improvement of the affected body region due to an improvement of cerebral plasticity processes .

The VSD produces parallel visual and audio signals when a minimal touch is applied at the site (body part) with a missing nerve sensory sensation (i.e. by a finger tip). A visual/audio signal is produced at the or within minimal distance of the affected site (body part), i.e. close to the individual finger. A signal dependent on applied pressure is produced, the audio signal differing in height or tone or rhythm, the optical signal differing in colour or brightness or pattern. The VSD can be programmed to produce a specific signal dependent on the site e.g. different colours (e.g. by differently coloured LEDs) /tone (different- sound or height or tone or rhythm) at different fingers.

Claims

Claims :

1. Device for re-learning sensitivity comprising one or more sensors, said sensors being sensitive to contact and pressure, an audio signal producing unit and a visual signal producing unit, said audio signal producing unit and said visual signal producing unit being designed for receiving contact and pressure signals from the sensor (s) and for producing audio signals and visual signals in correlation with said contact and pressure signals .

2. Device according to claim 1, characterised in that the audio-signal producing unit and the visual-signal producing unit are combined in a single audio and visual-signal producing unit.

3. Device according to claim 1 or 2, characterised in that the soft and mouldable material comprising one or more sensors is designed for receiving a human hand.

4. Device according to claim 3, characterised in that the soft and mouldable material comprises 5 sensors for 5 finger tips of said human hand.

5. Device according to any one of claims 1 to 4, characterised in that the audio-signal producing unit comprises an electronic impedance-device controlled by a MIDI-Sequencer .

6. Device according to any one of claims 1 to 5, characterised in that the visual-signal producing unit comprises at least two different light emitting diodes (LEDs) in two different colours.

7. Device according to any one of claims 1 to 5, characterised in that the visual-signal producing unit comprises a monitor, preferably a flat screen monitor.

8. Device according to any one of claims 1 to 7, characterised in that the visual-signal producing unit is integrated into the sensor (s) .

9.: Method for measuring contact and pressure at a sensor using the device according to any one of claims 1 to 8, characterised in that a patient contacts the sensor, whereby the device creates a visual and/or an acoustic signal (contact signal) ; then allowing the patient to increase the pressure onto the sensor; if the pressure onto the sensor increases over a predetermined pressure level the device creates a (further) visual and/or a (further) acoustic signal (pressure signal) being different than the contact signal.

10. Method according to claim 9, characterised in that the visual and/or the acoustic signal is created at the sensor or within a short distance to the sensor.

11. Method according to claim 9 or 10, characterised in that the visual contact signal differs from the visual pressure signal in colour, brightness and/or flashing pattern.

12. Method according to any one of claims 9 to 11, characterised in that the audio contact signal differs from the audio pressure signal in tone height, sound and/or rhythm.

13. Method according to any one of claims 9 to 12, characterised in that the visual or audio signal is different for different sensors .

14. Method according to any one of claims 9 to 13, characterised in that the patient contacts five sensors of the device with the five fingers of one hand.

15. Method according to claim 14, characterised in that each of the visual and/or the acoustic signal of the five sensors is different from each other.

16. Method according to claim 15, characterised in that the visual and/or the acoustic signal of the five sensors is created at the sensor or within a short distance to the finger on the sensor.

17. Method according to any one of claims 9 to 16, characterised in that the device creates a visual signal as contact signal,, preferably combined with an acoustic signal.