Results of stimulated sfemg which use data of region of motor points of the extensor digitorum communis muscle in Vietnamese

Objectives: To compare the results of stimulated SFEMG which use data of region of motor points of the extensor digitorum communis (EDC) muscle in Vietnamese. Subjects and methods: 63 subjects were enrolled in the study, in which 32 subjects performed with stimulating SFEMG in EDC muscles with new method and 31 subjects were with the classic method.

RESULTS OF STIMULATED SFEMG WHICH USE DATA OF REGION OF MOTOR POINTS OF THE EXTENSOR DIGITORUM COMMUNIS MUSCLE IN VIETNAMESE

Le Tu Quoc Tuan*; Nguyen Van Chuong** SUMMARY

Objectives: To compare the results of stimulated SFEMG which use data of region of motor points of the extensor digitorum communis (EDC) muscle in Vietnamese Subjects and

methods: 63 subjects were enrolled in the study, in which 32 subjects performed with

stimulating SFEMG in EDC muscles with new method and 31 subjects were with the classic method Results: For classic method, mean MCD = 32.90 ± 18.45 and 36.94 ± 21.38 for new method, p = 0.426 It showed that the MCD values obtained to diagnose myasthenia gravis (MG) in the usage of new method were more stable than when using classic method On the other hand, the time to finish a stimulating SFEMG in the new method was shorter but in classic method, electric intensity was smaller It needs to have larger data to confirm the efficacy of this new method in improving stimulated SFEMG technique of EDC muscle, which is one of the current challenges in clinical medicine

* Keywords: Simulated SFEMG; Myasthenia gravis; Extensor digitorum communis

INTRODUCTION

Single-fiber EMG is the most sensitive

electrophysiological method for the

determination of neuromuscular dysfunction

especially in mild cases (ocular MG) and

provides an extremely sensitive assessment

of the function of single neuromuscular

junctions in situ However, substitute

disposable concentric needle electrode (CNE)

for special single fiber needle to record

single-fiber potentials, electromyographers

get some technical difficulties

One of the two methods of performing

the technique of single fiber EMG is

stimulated SFEMG The principle of this

technique is to place a stimulating electrodes (needle electrodes or disc electrodes) so that it is close to the end plate of the motor nerve that innervate the muscles (usually the obicularis oculi and the EDC); then use a recording electrode (CNE needle) to measure jitter (MCD) -results from fluctuations in the time it takes for endplate potentials (EPPs) to reach the threshold for muscle AP generation The motor points of the skeletal muscles, anatomists’ and physiologists’ main interest, have recently drawn much attention from researchers in the field of functional electrical stimulation The muscle motor point has been defined as the entry point

* Trieu An Hospital

** 103 Military Hospital

Corresponding author: Le Quoc Tuan (ltqtuan@gmail.com)

Date received: 20/08/2017

Date accepted: 28/09/2017

of the motor nerve branch into the epimysium

of the muscle belly [1] If stimulating

electrode is inserted closed to the terminal

branch of motor nerve which innervated

target muscle (motor points of skeletal

muscle), the electricity will be lower and the

time to perform the technique will be shorter

Because EDC muscle has a large number

of MUPs (around 200 MUPs) and CNE with the radius of the receiving signals is large, so it is difficult and interfere in practice That is why, Stålberg E., Sander D.B has recommended not to use EDC muscle regularly in clinical practice [3]

Stimulated SFEMG at EDC muscle (axonal stimulation)

Figure 1: Principles of technique of stimulated SFEMG

A Figure illustrates the principles of technique

B Figure illustrates the axonal stimulation

SUBJECTS AND METHODS

1 Subjects

To compare 63 results of stimulating

SFEMG in EDC muscles, of which 31 results

were applied classic method (insert

stimulating needle - monopolar needle -

into EDC by palpate) and 32 results used

new method (insert stimulating needle -

monopolar needle - into EDC with estimating

an area - near terminal motor points) All results were done at the EMG laboratory

at Nguyen Hoang Medical Center from May 31st 2017 to September 28th, 2017

2 Methods

Case series report

Patients were examined by neurologists from many hospitals and medical centers

in Ho Chi Minh All of them were done

repetitive nerve stimulation (RNS) before

doing SFEMG 31 patients were done

stimulating SFEMG with ordinary method

before 10th September and 32 patients were done stimulating SFEMG with new method after this time

Figure 2: Anatomical basis for injection of stimulating needle into the EDC muscles

- In new method we use ruler to

determine the area to insert stimulating

needle-monopolar needle - into EDC This

region is located on the coordinate axis:

X-axis: 74 → 84 mm, Y-axis: -7 → 3 mm

in the position of about 1/5 - 2/5 proximal

of the D-OX axis (figure 2) Then we also

use electric stimulation to make EDC move

slightly before doing SFEMG

The distance between of the two

electrodes was approximately 10 - 15 mm

The stimulation rate was 10 Hz with a

stimulus duration of 0.05 ms All of patients

were done stimulated SFEMG in EDC with

recording electrode by new smallest CNE

(30G, 25 mm, Natus, USA) For each

patient, a minimum of 10 - 15 potentials

was sampled to calculate MCD in order to

confirm positive and 30 potentials were

sample to confirm negative In the case of monitoring the clinical status, MCD which was used for 30 recordings should be made for stimulation SFEMG studies We also practised SFEMG with both methods

(classic and new) for nine patients who

agreed after being explained; the interval between classic method and new method was 9 - 60 days

Only patients who performed SFEMG in the EDC muscle during the initial examination and pure ocular muscle weakness were included in the study

The study was performed on the Viking EDX system (Natus, 2017) version 22.0 with

a recording bandpass of 1 - 10 kHz Stimulation of the radial nerve was performed with the disposable monopolar

0

-10

-20

-30

70 60

4

0

3

40 30

needle cathode (30G, 37 mm, Natus, USA)

and the anode is disc electrode placed on

the skin near EDC

- In classic method: We insert stimulating

needle-monopolar needle into EDC by

palpation and use electric stimulation to make EDC move slightly before doing SFEMG

We use amplitude level technique to measure jitter (MCD)

RESULTS

1 Some characteristics of the subjects.

62 results of 49 patients were done (21 males and 28 females) Mean age was

40.90 ± 14.65 (ranged 17 - 71 years old)

By the t-test, the measurements did not have statistically significant difference in

gender (male and female) and position (left side and right side) (p > 0.05), so we add

up each of these groups in turn for descriptive statistics

2 Compare the results of two methods of SFEMG

Results of stimulating SFEMG is illustrated by a graph (figure 3):

Figure 3: Results of stimulating SFEMG

(negative results in the left, positive ones in the right)

Table 1: Jitter analysis in classic and

new method

Jitter analysis in classic and new method

(n = 31)

New method (n = 32)

Mean MCD (µs),

It showed that the MCD values obtained

to diagnose MG with new method is more

stable than in classic method But in the

new method, the time to finish a stimulating

SFEMG was shorter and electric intensity

was smaller in classic method The number

of jitter when using classic method was

bigger compared to new method because

sample of classic method was bigger than

that of new method

We got all results SFEMG with new method

However, one patient who was performed

with classic method had to stop the procedure

because this patient complained a pain

and the EDC muscle was swollen at the

position of injected stimulating needle

DISCUSSION

According to Stålberg E, Sander D.B,

it is difficult to measure jitter with CNE in

the ED muscle, particularly with electrical

stimulation This may reflect different

organization of muscle fiber within the

motor unit in larger muscles compared with

facial muscles Thus, Stålberg E, Sander

D.B do not recommend measuring CN

jitter in the ED in routine clinical practice

But we think that stimulating SFEMG with

new method makes it easier and can be

done on more patients than in classic

method To the best of our knowledge,

no previous studies practise stimulating SFEMG based on estimate an area - near terminal motor points - in which inject electrode for stimulated SFEMG in EDC muscle Because the number of patients

in our study is small, we think that it needs

to have larger data to conclude the efficacy

of this new method

CONCLUSION

The findings of the study have revealed

a new approach of stimulating SFEMG in EDC muscle Based on this approach, practitioners hope to improve technique of stimulated SFEMG in EDC muscle, which

is one of the current challenges in clinical

medicine [3]

REFERENCES

1 Safwat E.D, Abdel-Meguid E.M Distribution

of terminal nerve entry points to the flexor and extensor groups of forearm muscles - an anatomical study Folia Morphol 2007, Vol 66, No 2, pp.83-93

2 Sander D.B Single fiber EMG In:

Aminoff M., Daroff R.B.(eds) Encyclopedia of the Neurological Sciences Vol 4, 2nd Edition, Academic Press 2014, pp.169-171 Doi:10.1016/B978-0-12-385157-4.00543-1

3 Stålberg E, Sanders D.B, Ali.S, Cooray

G, Leonardis L, Loseth S., Kouyoumdjian O.A.

Reference values for jitter recorded by concentric needle electrodes in healthy controls: a multicenter study Muscle Nerve 2016, 53, pp.351-362

4 Stålberg E, Tronjeli, J.V, Sanders D.B

In: Single fiber Electromyography 3rd edition Edshagen Publishing House 2010

5 Yu Zhou Guanl, Li Ying Cui, Ming Sheng Liu, Jing Wen Niu Single fiber electromyography

in the extensor digitorum communis for the predictive prognosis of ocular myasthenia Gravis: A retrospective study of 102 cases Chinese Medical Journal 2015, Vol 128, Issue 20