For Muscular Hypertonus Our Experience With Craniomandibular Disorders

While it is easy enough to apply NCT for challenging a painful condition, it is more difficult to demonstrate that needle contact can reduce muscular hypertonus.

I have always been interested in finding an ideal research model in which the stimulation of one auricular point could change the hypertonus of a given muscle. One day, by chance, while examining a patient with bruxism with Dr Renzo Ridi, we found the right key: the patient, sitting in the dentist's chair, presented neck stiffness he had had since awakening. I tried to relax his muscles with ear acupuncture but surprisingly I did not find any sensitive point on the commonly accepted representation of the neck and the cervical vertebrae.

Moving the tip of the algometer downward to the ear lobe, however, I found a very sensitive point which I later realized to be located within the Chinese occiput area (AT3 zhen). On that morning the patient was scheduled for an EMG investigation according to the technique proposed by Jankelson.12 In this procedure some electrodes are attached bilaterally on fixed areas corresponding to masticatory muscles such as temporalis anterior, masseter, digastric and temporalis posterior. However, in this case and in the trial which followed, using Myotronics EM2, we replaced the recording on the latter with the sternocleidomastoid.

After a base recording I pressed the sensitive point with the tip of the algometer as usual in the PPT, and we were excited to notice that the first two muscles in particular lost their tension, measured in mV, during the following minutes. This fortunate case was the first of a series which led us finally to devise a randomized controlled trial (RCT) for demonstrating the value of ear acupuncture in reducing muscular hypertonus.

In a pilot study made on 10 consecutive patients with bruxism, we tried first to find an answer to the question: to what extent do diagnostic maneuvers act as a confounding factor and provoke a variation of muscular tension?

Actually, whatever auricular diagnostic technique is chosen, it may act per se as a therapeutic stimulation; this fact does not usually receive sufficient consideration.

We first evaluated ESRT, which we thought was the least invasive procedure. Indeed, the pressure exerted on the skin by the spring-loaded electrode can be considered negligible (see Ch. 6); however, we did not know if the electrical current flow through the ear could also be considered negligible. We decided to test the point with the lowest electrical resistance within the occiput area. One hour before starting EMG, comparing the right and left auricles only one point was chosen. The point was marked with ink and 1 hour later, after a base recording of 5 minutes, it was again identified with Agiscop. A further period of 14 minutes continuous recording was then performed (Fig. 8.9A). Taking this opportunity we decided to evaluate also the stimulation effect of NCT, and after needle contact for 10 seconds we carried out a second EMG recording for the same period of 14 minutes (Fig. 8.9B).

Comparing the EMG variations in the two periods, we can see that the electrical current flow through the occiput point during the ESRT procedure temporarily reduces muscular tension. In the last 5 minutes compared to the first 5 minutes, however, the muscular tension worsens significantly in a possible rebound effect (Table 8.1). The response to NCT is different and the reduction of muscular tension is progressive during the whole period of recording, and the last 5 minutes show a significant improvement compared to the first.

Apart from the opposite influence of ESRT and NCT on muscular tension, this pilot study gave us essential information regarding the physiology of auricular acupuncture. NCT performed on one side could induce a significant EMG variation not only on the ipsilateral but also on the contralateral temporalis anterior muscle (Table 8.1).

Our findings led us to organize an RCT13 on three homogeneous groups of patients with malocclusion rated with Helkimo's index of the clinical and dysfunctional state (CDI) of the masticatory system.14

The patients belonged to a selected group that I had treated previously with acupuncture for disorders such as chronic neck and back pain, vertigo, atypical facial neuralgia, migraine, etc. One common characteristic in these patients was that the result of the treatment had been rated by me in the follow-up as unsatisfactory and not durable. Given the possibility that craniomandibular disorders may be responsible for postural changes in the case of chronic myofascial pain, Dr Ridi made a complete evaluation of the stomatognathic system of these patients, including EMG.

The patients were included on the day of experimentation if their values of muscular tension in mV, in at least one muscle, were higher than the normal range established by Myotronics-EM2. The normal range was 1.5-2.5 mV for temporalis anterior, 1.0-2.0 mV for the masseter and 1.5-2.5 mV for the digastric muscle. Out of a total of 61 subjects examined, only 43 were included and randomized in three groups. In the first group NCT was performed for 10 seconds and in the second a 0.20 x 15 mm needle was placed on the same point; the third group acted as the control group and received no intervention for the whole period of observation. The EMG recording time was brought up to 30 minutes for a total of 120 consecutive recordings.

The EMG variations on the total number of eight muscles were compared with t-test for independent samples (Table 8.2). Both stimulations were superior to the control group in reducing the electrical activity of all muscles except the sternocleidomastoid. As regards the comparison between the insertion of the needle and the simple contact, acupuncture results were superior to NCT only for the right temporalis and left digastric. The reaction to the stimulation of the sternocleidomas-toid was different than in the other muscles but it has to be pointed out that the sternocleidomastoid does not participate directly in mastication. This is a further reason for possibly considering the occiput area as specific for bruxism and malocclusion.

Digastric Muscle And Bruxism

Fig. 8.9 Cubic regression line for muscular tension (mV) and consecutive EMG recordings of contralateral temporalis anterior (Ta) muscle according to the modified Myotronics EM2 procedure in 10 patients with bruxism; after electrical detection of the identified point (A); after NCT for 10 seconds of the identified point (B). Twenty recordings correspond approximately to 5 minutes.

Fig. 8.9 Cubic regression line for muscular tension (mV) and consecutive EMG recordings of contralateral temporalis anterior (Ta) muscle according to the modified Myotronics EM2 procedure in 10 patients with bruxism; after electrical detection of the identified point (A); after NCT for 10 seconds of the identified point (B). Twenty recordings correspond approximately to 5 minutes.

Table 8.1 Comparison between the mean values of muscular tension in the ipsilateral and contralateral temporalis anterior (Ta) muscle, after ESRT and subsequently after NCT

Method

Mean value

95% C.I.

P

First 20 EMG Last 20 EMG recordings (mV) recordings (mV)

Mean difference

Lower

Upper

Ipsilateral Ta

ESRT

2.93

3.57

-0.64

-0.89

-0.39

<0.001

NCT

3.25

2.50

0.75

0.57

0.93

<0.001

Contralateral Ta ESRT

2.78

3.21

-0.42

-0.68

-0.17

<0.005

NCT

2.88

2.24

0.64

0.51

0.76

<0.001

Ta = temporalis anterior

Table 8.2 Comparison, with t-test for independent three groups (acupuncture, needle contact, control)

samples, of the EMG variations

in the eight muscles of

Muscle

Acupuncture vs. control

NCT vs. control

Acupuncture

vs. NCT

t-test

P value

t-test

P value

t-test

P value

Right Ta

8.429

<0.005

6.346

<0.005

3.308

<0.005

Left Ta

7.012

<0.005

5.884

<0.005

0.681

NS

Right Mm

4.425

<0.005

6.750

<0.005

1.590

NS

Left Mm

6.542

<0.005

3.580

<0.005

0.888

NS

Right Da

5.101

<0.005

3.948

<0.005

1.936

NS

Left Da

6.360

<0.005

3.481

<0.005

4.647

<0.005

Right SCM

0.246

NS

1.855

NS

-2.077

<0.05

Left SCM

-4.167

<0.005

0.157

NS

-4.987

<0.005

Ta = temporalis anterior; Mm = masseter; Da = digastric; SCM = sternocleidomastoid

Ta = temporalis anterior; Mm = masseter; Da = digastric; SCM = sternocleidomastoid

The conclusions of our RCT were that:

we had the rare opportunity to study the stimulation effect of a single point, how it has been possible with the acupuncture point PC6 on nausea. The result in our group of patients indicates the possibility that EMG could be a sensitive tool for measuring the effects of auricular stimulation also in other medical conditions. As regards NCT, this modality most probably should be considered an intermediate method of stimulation between true acupuncture and non stimulation.13

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