Background of the invention [0002] Classical study of muscle activity in human requires the use of cables linked to an acquisition unit.

EMG activity is recorded either using needle electrodes/wires inserted in the muscle, either using surface EMG electrodes. So far, there is no technique available to estimate visually and in colour the voluntary (such as a movement of the hand or the neck) or involuntary (such as tremor or dystonia) muscle activity, taking into account ergonomics (a tool which would be lightweight, portable and without cables), and non-invasively. Such a tool would be of great help and benefit for the non- invasive follow-up of patients and for the diagnosis of neuromuscular diseases. For instance, the diagnosis of diseases like torticolis, hand dystonia, upper limb tremor would be easier.

Summary of the invention [0003] The new sensor according to the invention combines the use of active differential electromyographic

electrodes fixed directly on the skin (2) such as a Delsys electrode (www. delsys com/products/electrodes. htm) coupled to digital video display preferably coupled to semi- conducting polymer LEDs (7). Semi-conducting polymer LEDs (7) are electroluminescent polymers such as the one described by Braun D., Semi-conducting polymer LEDs.

Materials today. June 2002 ; Elsevier Science, pp. 32-39.

These polymer LEDs (7) are flexible and present switch on and off characteristics suitable for video display (10) applications.

[0004] Thanks to the development of active EMG electrodes, the signal-to-noise ratio is improved. These electrodes are directly fixed to the skin (2) of a patient.

The signal is amplified directly on the skin (2) and filters can be implemented in the amplifier.

[0005] The enclosed figures 1 to 3 show the characteristics of the (non-invasive, lightweight, ergonomic and portable by the patient) sensor, which can be applied directly upon the skin (2) of a patient in order to characterise the level of muscle (1) patient activity. The EMG electrode comprises an electrode interface (3), an active amplifier (4), a battery (5), an electronic circuit (6) connected to a semi-conducting polymer LED (7).

[0006] In the figure 2 is presented the basic principle of the sensor presenting a video display for two colours. The EMG signal is therefore amplified and filtered. A rectifier (8) or inverter (11) can also be used.

[0007] The figure 3 presents a variant of the (colour-EMG) sensor according to the invention, which comprises a digital display (10) of the EMG activity.. The numbers will appear according to the level of EMG activity.

Said system comprises also a classical analogue converter (9) for a direct visual display.

[0008] The sensor according to the invention presents the following advantageous characteristics: [0009] The (colour-EMG) sensor of the invention is fixed on the skin of the neck in patients suffering from torticolis. The sensor informs the observer of the level of muscle hyperactivity (the colour selected is dependent on the level of EMG activity). This procedure will improve the diagnosis, leading advantageously to a drug administration in the early stages of the disorder.

[0010] Two units of (colour-EMG) sensor of the invention are fixed respectively on the flexor carpi radialis muscle and extensor carpi radialis muscle in a patient suffering from a upper limb tremor. The LEDs flash asynchronously in Parkinson's disease, whereas they flash synchronously in Essential Tremor. Furthermore, the level of EMG activity of each muscle will appear thanks to the colour flashing. Therefore, this technique can be used non- invasively or invasively, with the introduction of two fine wire electrodes in the muscle of the patient by the general practitioner.

[0011] This invention allows an analysis of the activity of muscle groups during clinical examination.

Several (colour-EMG) sensors are fixed on the patient's lower limbs at the level of the thighs and the legs. This technique will help the neurologist to identify muscles which are overactive and those that are under-active during gait.

[0012] Furthermore, this sensor allows a diagnosis of primary orthostatic tremor (POT). The (colour-EMG) sensor of the invention will flash at a high frequency (13 to 18 Hz) if fixed at the level of weight-bearing muscles while the patient is standing (this disorder is characterized by high-frequency synchronous discharges at a frequency of 13 to 18 Hz).

[0013] The sensor can be used for the detection of myoclonus. The (colour-EMG) sensor of the invention will detect the brief and involuntary contractions (usually with a duration of less than 150 msec) by flashing on the skin.

[0014] A"dream"for the rehabilitation specialists is to estimate visually and preferably non-invasively the activity of the muscle groups (agonists/antagonists /synergic) during rehabilitation. The (colour-EMG) sensor of the invention will help in this task by informing which muscle is active as compared to the other ones.

[0015] In addition, the sensor of the invention allows a non-invasive analysis of muscle activity following a hand grafting. These patients need to take immunosuppressive drugs. Therefore, needles are usually avoided. The (colour-EMG) sensor of the invention will help the therapist to follow the recovery.

[0016] The sensor of the invention can be used for analysis of EMG activity non-invasively in babies and in children, especially in intensive care units.

[0017] The use of the (colour-EMG) sensor is also proposed in sports to estimate the level of contraction.

[0018] For a research perspective-, the sensor comprises fine wire electrodes (inserted in the muscle), the (colour-EMG) sensor will be used to analyze the muscle activity in neuromuscular diseases. Advantageously, the analysis of the patient's muscle activity will be improved with the sensor according to the invention because the signal-to-noise ratio is increased compared. to a known technique that requires long connection means between a sensor and a recording apparatus.

[0019] A last aspect of the present invention is related to a method for measuring muscle activity of the patient, which comprises the step of maintaining the interface with

electrodes of the sensing device according to the invention upon the patient's skin for a sufficient time to obtain a measure and, possibly a recording of muscle activity of the patient.

[0020] Using several groups of wires inserted in the muscle or using multi-channels needles, the colour-EMG will allow to analyze simultaneously the activity of distinct groups of muscle fibers, to detect overactivity ou underactivity of different portions of the muscle