• Exploration of non-invasive electrophysiological approaches: surface electromyography (EMG)
A fundamental axis of our research has developed around the use of surface electromyography (EMG) as a diagnostic tool and for patient follow-up. This technique uses high-resolution spatial electrodes to study muscle at its functional level: the motor unit. It is a non-invasive examination, allowing to respond to the clinicians’ will and for the patients themselves to eventually have a non-traumatising follow-up examination, which can be repeated without constraint. At present, the electrophysiological examination of neuromuscular pathologies is performed using needles, which limits their use for the follow-up of patients.
Studies undertaken in this axis include fundamental research on the analysis of the recruitment of motor units and clinical studies of action potential trains, such as the analysis of neuromuscular excitability and exercise fatigue in healthy and sick individuals.
• Development of fatigability tests
A series of non-invasive exploration tests was developed in order to apprehend the physiopathological mechanisms of exercise fatigue, at the cortical, medullary, nervous and muscular levels.
After validation in healthy individuals, these tests were applied to the study of neurological pathologies primarily affecting the central nervous system (multiple sclerosis), the peripheral nerve (various neuropathies) or muscle (myotonic dystrophy).
The speed, painless nature and repeatability of these tests allow to consider their future application in neurophysiological practice to ensure the longitudinal follow-up of patients or the evaluation of the effects of a treatment.
Example of a motor responses obtained before and after a 45-second
maximum voluntary strength exercise of 60% fatigue. The duration of the signal
represented is 50 ms
• Myotone Test
The Laboratory is developing the Myotone Test, a quantitative evaluation test of myotony. Currently, no test exists that allows such routine evaluation.
The principle is straightforward. The patient must maintain a set level of effort, after evaluation of his maximum voluntary force, and to release this effort as quickly as possible after being instructed to do so. The relaxation times of the force represent indicators of myotony.
Like the Grip Test, the Myotone Test is entirely managed by dedicated software. According to patients, it is amusing with hardly any constraints since it lasts less than ten minutes. Nevertheless, it remains to be validated before being used in clinical practice.
Measurement principle of myotonia by the MyoTone
Test. Measurements of strength relaxation times constitute a quantified
indicator of myotonia. Relaxation times can be fairly long for a Steinert’s
myotonic dystrophy patient, as shown by the examples on the right.
• TaToo
TaToo (tremor assessment tool) is a device used to measure tremor during a grasp between the thumb and forefinger. It is intended for the evaluation, diagnosis and follow-up of individuals affected by diseases characterized by tremors. The principle of the prototype, which was developed by Jean Philippe Bemma during his second year internship (Cachan Technology University), has been validated. A device wireless is under development.
• Dynamic muscle force measurement in neuromuscular diseases
This is a new isokinetic knee flexor and extensor evaluation method using a continuous passive motion (CPM) mode developed by Dr. Vincent Tiffreau for the Inter-University Diploma of neuromuscular pathologies. The reliability of the method was validated by a study undertaken in 15 patients with neuromuscular pathologies of varying severity. This method was considered to be of great interest for the evaluation of weak patients suffering from neuromuscular disorders (Tiffreau et al, 2007).
