In che modo le griglie bidimensionali di elettrodi ci aiutano nell interpretazione del segnale EMG di superficie?

Transcription

1 Nuove evidenze per l'acquisizione ed interpretazione del segnale EMG: dal bipolare al multicanale e ritorno In che modo le griglie bidimensionali di elettrodi ci aiutano nell interpretazione del segnale EMG di superficie? Taian Vieira, Ph.D. taian.vieira@polito.it Laboratory for Engineering of the Neuromuscular System (LISiN), Politecnico di Torino, Italy Centro Congressi Torino Incontra, Torino. Mercoledì 4 Ottobre 2017

2 Presentation outline From bipolar to high-density surface electromyograms (EMGs) How 2D grids of electrodes may help us with the unambiguous interpretation of surface EMGs Examples of applications exclusively focused on the use of 2D grids of electrodes

3 + Voltage 100 Temporal representation of surface action potentials: a single active motor unit 10 pps 0 Time - Skin Fat Muscle

4 + Voltage 100 Temporal representation of surface action potentials: two active motor units 0 Time - Skin Fat Muscle

5 Anatomical and physiological information provided by high-density electromyograms Tendon Waveform of motor unit action potentials (depend on the number of fibres, the jitter of end-plates, the depth of motor unit territory and the conduction velocity, among other factors) Tendon location (extinction of potential) otor unit (MU) Innervation Zone motoneuron (axon) (phase inversion) End-plate Tendon Tendon location (extinction of potential) Conduction velocity (indicated by the V pattern)

6 200 μv Rows Position (mm) Different units are observed in different regions across gastrocnemius 3 6 Columns Merletti et al 2010 (Crit Rev Biomed Eng 38:347-79) forward CoP CoG 4 6 Medial gastrocnemius Lateral gastrocnemius 10 s s

7 Ankle 100 µv Grids of electrodes provide a representative estimation of the timing of gastrocnemius activity EMG detected proximally Dos Anjos et al 2017 (Front Hum Neurosci 11:190) EMG detected distally RMS amplitude greater than the background, rest level Time (s) Global, representative estimation of periods of activity ACTIVE NOT ACTIVE ACTIVE Time (s)

8 Pennation angle = 0 Muscle unit parallel to surface electrodes Pennation angle = 20 Muscle unit pennate in the depth direction d Fat tissue Skin 5 ms A.U. Mesin et al. J Biomech ms A.U.

9 The spatial distribution of surface EMGs is associated with the territory of motor units. Motor unit with small territory Motor unit with large territory Vieira et al 2011 (J Physiol 589:431-43) Fat tissue Skin Array of electrodes Tibial nerve Muscle fibre Ankle + +

10 3.3 mv Rows (cm) ARV amplitude (µv) Topography of active fibres in the medial gastrocnemius muscle Vieira et al 2015 (J Neurophysiol 114: ) Stimulation electrode US probe Matrix of electrodes (1 cm IED) th stim. level (12-14 ma) 8 th stim. level (14-16 ma) Columns of single differential, incremental M-waves

11 Ankle Rows of channels (inter-electrode distance = 1 cm) Instantaneous EMG amplitude (mv) Is it then not possible to detect propagating potentials from medial gastrocnemius? Gallina et al 2013 (J Electromyogr Kinesiol 23:319-25) Raw surface EMGs EMG Image Prints of electrodes on the skin Rows Columns ms Medial

12 Ankle 0.3 mv 0.5 mv Knee Why can we observe propagating potentials only for electrodes positioned at the more distal regions? Fat tissue gastrocnemius fascicles skin Hodson-Tole et al (J Electromyogr Kinesiol 23(1):43-50) Electrodes located over the end of different muscle fibres + 5 ms Medial Gastrocnemius Electrodes running over the same group of muscle fibres + 20 ms Surface electrodes Array of surface electrodes Localised, atypical motor unit action potential (MUAP) MUAP with typical features of skin parallelfibered muscles

13 Why is propagation appreciated only from top to bottom? Is And it really from unidirectional? bottom to top?

14 Instantaneous EMG amplitude (mv) Propagation is not unidirectional. Potentials propagate in oblique direction Electrodes and muscle fibres' location Raw, surface EMGs EMG Image Muscle fascicles Gallina and Vieira 2015 (Muscle Nerve 52: )

15 Local representation of activity in different skeletal muscles has been observed by different researchers and with different technologies. Kinugasa et al J Appl Physiol 2005; McLean and Goudy Eur J Appl Physiol 2004; Tamaki et al J Appl Physiol 1998; Segal and Song Arch Phys Med Rehabil 2005; Staudenmann et al J Electromyogr Kinesiol 2009; Watanabe et al J Biomech 2016; Wolf et al J Electromyogr Kinesiol 1998;

16 Some examples on the application of 2D surface electromyography Revisiting muscle function from an electrophysiological perspective

17 16 rows Root mean square amplitude of motor unit action potentials Proximal Interpretation of surface EMGs demands prior knowledge on the architecture of specific muscles Lateral Axonal branch supplying proximal fibres 26 mv 1 cm 8 columns Vastus medialis fibres 1 cm Patella 0.2 mv Subject 14, motor unit 8 and motor unit ms Patella

18 Occurrences Occurrences MUs have relatively small territories and a range of fibres inclinations Gallina and Vieira 2015 (Muscle Nerve 52: ) N = 77 MUs Fiber orientation (FO) Median: th perc.: mm Angle (deg) Sigma (mm) Estimated territory size (σ) N = 77 MUs Median: 20 mm th perc.: mm

19 Propagation of action potentials in oblique direction is typically observed for pinnate muscles Sartorius Vastus Medialis Rectus Femoris Vastus Lateralis What is so especial about the pinnate, vastus medialis muscles? Intramuscular differences in fiber orientation can be observed in vastus medialis (Smith et al., 2009) Proximal fibers: Knee extension Distal fibers: Patellar tracking (Lin et al., 2004) Patella

20 Regionalised, rectus femoris function during gait Watanabe et al 2014 (J Biomech 47:3502-8)

21 Some examples on the application of 2D surface electromyography Myoelectric manifestation of fatigue

22 Cranial Rows of channels (8 mm IED) RMS amplitude (uv) C7 Rotation of motor units delays fatigue Farina et al 2008 (J Electromyogr Kinesiol 18:16-25) RMS images for different endurance times 0% 25% 50% 75% 100% Columns of channels (8 mm IED) 10 Acromion Lateral

23 LISiN, Torino 1 MOUSE USING (30 seconds, mean ARV maps): LEFT Max = 6 μv 1 - WRIST SUPPORT 1 RIGHT Max = 34 μv 2 Max = 2 μv 2 - FOREARM SUPPORT 2 Max = 9 μv 4 cm μv 3 - NO SUPPORT 10.4 cm 20 μv Max = 9 μv Max = 33 μv 10 μv 0 μv

24 Do sweep rowers activate their back muscles asymmetrically? Boat rotates to the right side Asymmetrical activation of back muscles might lead to back pain Parkin et al J Sports Sci Asymmetrical activation seems crucial for boat stabilisation

25 Even in a laterally stable condition, 2D EMGs reveal side differences in the activation of back Readi et al 2015 (Scand J Med Sci Sports 25:e339-52)

26 Some examples on the application of 2D surface electromyography Distinguishing the activity of deep and superficial muscles

27 1 cm Is it possible to distinguish the activity of internal (IO) and external (EO) oblique muscles? Brown and McGill (2010) Clin Biomech Ultrasound images taken during: Rest Contraction External Oblique Internal Oblique Transverse abdominis Medial Muscle thickness

28 With a grid of electrodes we tested if, from propagation direction, internal and external oblique activity may be distinguished in the surface EMGs Contralateral trunk rotation Our hypothesis External oblique muscle (superficial) Ipsilateral trunk rotation Internal oblique muscle (deep) Ilium Ilium Grid of 64 surface electrodes (8 mm IED) Rectus sheat

29 The amplitude of surface EMGs distributed along different directions during ipsilateral and contralateral trunk rotations Rows of single-differential EMGs (8 mm IED) Rows of single-differential EMGs (8 mm IED) Columns (8 mm IED) Columns (8 mm IED)

30 During ipsilateral trunk rotation, we could identify action potentials propagating towards the bottom-left corner Missing electrode Instantaneous, interpolated (4x) EMG image Grid of 64 surface electrodes (13 x 5 arrangement) 8 mm Active, IO fibres Action potential Innervation zone

31 During contralateral trunk rotation, we could identify action potentials propagating towards the bottom-right corner Missing electrode Grid of 64 surface electrodes (13 x 5 arrangement) 8 mm Instantaneous, interpolated (4x) EMG image Innervation zone Action potential Active, EO fibres

32 Some examples on the application of 2D surface electromyography Administration of botulinum toxin

33 Surface EMGs help in guiding the injection of the botulinum toxin Lapatki et al 2011 (Clin Neurophysiol 122:1611-6)

34 Some examples on the application of 2D surface electromyography Myoelectric control of prosthesis

35 EXTENSOR ACTIVITY Hand Open Two channels control of a hand prosthesis (near wrist amputation) S1 Co-contraction No action or lock Off Hand Close S2 FLEXOR ACTIVITY

36 What if EMGs from the forearm muscles could be collected with a grid of electrodes? Wrist Extension Thumb Extension Fingers Extension Wrist Extension

37 Summary of the lecture: detecting surface EMGs Bipolar detection (one or more pairs of electrodes): - Timing of activity - Amplitude - Frequency Linear array (longitudinal): - Innervation zone location - Tendon location - Conduction velocity Linear array (transversal): - Location of active muscle regions Carefully placed Global information Affected by crosstalk? Representative EMGs? Skin-parellelfibered muscle - Location of active regions in pinnate muscles 2D grid of electrodes: - Regional activation indistincly for any muscle - Muscle fiber orientation - Surface EMG decomposition

38 Sessione 3 Postura ed equilibrio O.17 (05/10/ :23) Motor unit plasticity in stroke survivors: altered distribution of gastrocnemius action potentials Taian Vieira, T. Lemos, L. Oliveira, C. Horsczaruk, F. Tovar-Moll, E. Rodrigues taian.vieira@polito.it Laboratorio di Ingegneria del Sistema Neuromuscolare (LISiN), Politecnico di Torino, Torino, Italia