Identification of innervation zone based on high-density EMG M-wave

recordings in healthy and stroke subjectsSheng Li, MD, PhD

Department of Physical Medicine and Rehabilitation University of Texas Health Science Center – Houston

Neurorehabilitation Research LaboratoryTIRR Memorial Hermann Hospital, Houston, TX

R24 Research Meeting, Chicago, 6.18-20, 2013

Introduction – Botulinum toxin injection for post-stroke spasticity management

Poststroke spasticity (PSS)-related disability is emerging as a significant health issue for stroke survivors. (Wissel et al. 2013)

Prevalence estimates of PSS were highly variable, ranging from 20-40%, thus causing a significant burden for survivors and caregivers (Zorowitz et al. 2013)

Botulinum toxin remains the first line treatment for focal spasticity management

Wissel J, Manack A, and Brainin M. Toward an epidemiology of poststroke spasticity. Neurology 80: S13-S19, 2013.Zorowitz RD, Gillard PJ, Brainin M. Poststroke spasticity: Sequelae and burden on stroke survivors and caregivers Neurology , 2013 80:S45-S52

Botulinum toxin blocks release of neurotransmitters (Acetylcholine) from the

presynaptic membrane of the motor endplate at the neuromuscular junction.

Jahn 2006

Botulinum Toxin Mechanism of ActionBotulinum toxin blocks presynaptic release of Acetylcholine at the neuromuscular junction

Detection of Innervation zone using high-density EMG recordings

Barbero M. Merletti R., Rainoldi A. (2012) Atlas of muscle innervation zones. Springer

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Detection of Innervation zone using high-density EMG recordings and M-wave

Endplate-Targeted injection using high-density EMG in healthy subjects

• 10 U Dyspot to the endplates of EDB• 10 U to contralateral side away from endplates• Measured by CMAP

Lapatki BG, van Dijk JP, van de Warrenburg BPC, and Zwarts MJ. Botulinum toxin has an increased effect when targeted toward the muscle's endplate zone: A high-density surface EMG guided study. Clinical Neurophysiology 122: 1611, 2011.

Effectiveness decreases with distance from Endplates: study vs. control side

Current clinical guidance is based on histological cadaver studies: Motor points in cadavers using whole-mount actylcholinesterase (AchE) staining

Amirali A, Mu L, Gracies JM, and Simpson DM. Anatomical localization of motor endplate bands in the human biceps brachii. Journal of clinical neuromuscular disease 9: 306-312, 2007.

MAS 0 1 1+ 2 3

Indication for botulinum toxin injection

• Patients who have moderate to severe spasticity need injection;• The goal of injection includes

• ROM, positioning, Pain management; Prevention of complications• To improve functions: ADLs, mobility and motor control

Need to detect innervation zone for stroke patients

• Pathological changes in spastic muscles occur after stroke• atrophy• contracture etc.

• NO study on motor points/innervation zone for spastic muscles

• Patients with moderate to severe spasticity need injection usually have minimum to no voluntary contraction of spastic muscles;

• Nerve stimulation is an alternative method to obtain EMG signals for innervation zone detection (M-wave method).

Overall goal

• To develop a method based on high-density EMG M-wave recordings to identify and evaluate innervation zone of spastic-paretic muscles in chronic stroke.

• The method could be used to improve targeting of botulinum toxin injection to the innervation zone, thus the efficacy of treatment.

Specific aims

• To identify and evaluate innervation zone in healthy and stroke subjects• To overcome technical difficulties (stimulation

artifacts during M-wave recordings)

• To optimize methods for automatic identification of motor innervation zone

• To re-evaluate EMG-torque relations in chronic stroke based on innervation zone analysis

IZ in healthy and stroke subjects

• Exp. Setting: as shown• N = 11 healthy subjs.• N = 10 hemiparetic stroke

subjects• Both sides• Two tasks:

• MVC • M-wave

Removal of stimulation artifact

Contaminated M waveReconstructed M Wave

Clean M waveReconstructed M-Wave

10 ms

1 mV

S t i m u l u s a r t i f a c t

C l e a n M w a v e

(a)

(b)

(c)

(d)

Methods of IZ detection

CORR MNF RMS0

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40

60

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100

120

Accu

racy

(%)

Automatic estimation method

RMS (µV) MNF (Hz) CORR

0 10 20 30 40 50

Ch

ann

el I

nd

ex

Time (ms)

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6.77 6.72 7.91 7.89 9.32 8.19 9.90 9.70 10.87 12.27 9.46 1.61 9.37 13.64 13.44 13.90

93 93 89 95 91 93 92 94 94 99 108 132 113 105 104 100

0.97 0.99 0.99 0.99 0.99 1.00 1.00 0.99 0.99 0.98 0.48 0.75 0.99 0.99 1.00

RMS: root mean square amplitude,MNF: mean frequency, CORR: cross correlation

Sample trials from a healthy subject

IZ location : 9 IZ location : 9

MVC trial M-wave trial

control

IZIZ

Sample trials from the nonimpaired side

IZ location : 10 IZ location : 11

MVC trial M-wave trial

Stroke IZ

IZ

IZ location : 10 IZ location : 10

MVC trial M-wave trial

Stroke IZIZ

Sample trials from the impaired side

Comparison of IZ in healthy subjects

Impaired side Non-impaired side

ID Age Gender Paretic MASStrength (in Nm)

IZ location (MVC)

IZ location (M-wave) Strength (in

Nm)

IZ location (MVC)

IZ location (M-wave)

1 57 F right 1+ 18 8 8 40 5 5

2 67 M right 1+ 25 10 8 73 8 7

3 61 M right 0 36 12 10 31 9 10

4 89 M left 1+ 12 9 9 42 10 10

5 76 M right 1 38 6 8 15 6 7

6 58 F left 1 6.5 9 8 19 5 6

7 59 F right 0 40 7 8 58 6 5

8 50 M right 1 21 10 10 52 10 11

9 47 M left 0 55 10 10 70 10 10

10 39 M right 1 12 9 9 58 9 9

average 26.35 9 8.8 45.8 7.8 8

Characteristics of stroke subjects

MVC IZ M-wave IZ7

7.5

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No difference in IZ location using dif-ferent EMG methods and between

two sides

impairednon-impaired

Comparison of IZ in stroke subjects

Re-evaluation of EMG-torque relations using high-density EMG recordings

• Exp. Setting: as shown• N = 10 hemiparetic stroke

subjects• Both sides• Tasks:

• MVC • Submax at 10, 20, 30,

40, 50, 60, 70, 80%MVC

Sample EMG and torque signals

A: Non impaired side B: Impaired side

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0 2 4 6 8 100

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0 2 4 6 8 100

Torque (Nm)

Time (sec)

EMG (µV)

Sample EMG-Force relations in all channels

Slope

EMG Channel

0 5 10 15 200

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Non impaired side

Impaired side

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Comparison of EMG-torque slope

Summary1. Global aver. Slope: non-impaired>impaired, 2. Highest slope: non-impaired>impaired3. Lowest (on IZ channel): non-

impaired>impaired4. consistent for all subjects

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Summary• Successful and reliable detection of IZ of biceps

in both healthy and hemiparetic stroke subjects;

• No difference in IZ location between impaired and non-impaired sides;

• No difference in IZ detection using MVC and M-wave methods;

• Re-evaluation of EMG-torque relations using high-density EMG

Future plan

• To develop a method based on high-density EMG M-wave recordings to identify and evaluate innervation zone of spastic-paretic muscles in chronic stroke.

• To compare efficacy of botulinum toxin injections to the innervation zone and using the traditional approach, based on the M-wave method.

Project-specific publications• Jie Liu, Sheng Li, Xiaoyan Li, Cliff Klein, William Z. Rymer, Ping Zhou (2013)

Suppression of stimulus artifact contaminating electrically evoked electromyography. Neurorehabilitation (in press)

• Jie Liu, Sheng Li, Faezeh Jahanrimi-Nezhad, William Z. Rymer, Ping Zhou (2013) Automatic innervation zone detection of spontaneous motor units in amyotrophic lateral sclerosis (under review)

• Jie Liu, Minal Bhadane, William Z. Rymer, Ping Zhou, Sheng Li (2013) Comparison of innervation zone based on high-density EMG and M-wave recordings in healthy and stroke subjects (in preparation)

• Minal Bhadane, Jie Liu, William Z. Rymer, Ping Zhou, Sheng Li (2013) Re-evaluation of EMG-torque relations in chronic stroke using high-density EMG recordings (in preparation)

Zev Rymer, MD, PhD (RIC) R24 HD050821-08 under subcontract with

Rehabilitation Institute of Chicago

Acknowledgement

Collaborators Minal Bhadane PhD (UTHealth)

Ping Zhou, PhD (RIC) Jie Liu, PhD (RIC)