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April2015 Vol.52 Issue:      2 Table of Contents
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Therapeutic Role of Repetitive Peripheral Magnetic Stimulation in Carpal Tunnel Syndrome

Amira M. El Gohary1, Heba Raafat1, Mye A. Basheer1,

Sandra M. Ahmed2, Marwa S. Shalaby1

Departments of Clinical Neurophysiology1, Neurology2, Cairo University; Egypt



ABSTRACT

Background: Carpal tunnel syndrome (CTS) is one of the most common causes of upper limb neuropathic pain and tends to increase in severity as the disease progresses. It can significantly affect motor performance and different activities of daily living. Appropriate management should be implemented from the time of its symptoms onset. Many non-surgical treatment procedures were previously researched. However, repetitive peripheral magnetic stimulation (RPMS) for the treatment of carpal tunnel syndrome is not in such lists. Objective: To evaluate the therapeutic effects of RPMS in carpal tunnel syndrome. Methods: Twenty participants were enrolled. Nerve conduction studies, Visual Analogue- pain- Scale (VAS) and RPMS were performed. Results: Significant pain reduction was found among patients with early CTS for up to a month after RPMS. Conclusions: RPMS can be considered as a noninvasive therapeutic tool for pain reduction in early CTS patients. [Egypt J Neurol Psychiat Neurosurg.  2015; 52(2): 133-137]

 Key Words: Carpal tunnel syndrome, Peripheral magnetic stimulation, Conservative pain relief, Visual analogue pain scale

Correspondence to Mye Ali Basheer, Faculty of Medicine, Cairo University, Egypt. Tel.:  +201001777179.  Email: mye.basheer@kasralainy.edu.eg

 





INTRODUCTION

 

Unilateral upper limb sensory and/or motor symptoms are often due to various neuropathies; carpal tunnel syndrome (CTS) is a common cause among them1. It occurs when the median nerve, which runs from the forearm into the palm of the hand, becomes squeezed at the wrist2. It is clinically “constellation of symptoms associated with compression of the median nerve at the wrist”3. 

Treatment of CTS can be classified as surgical and non-surgical. Non-surgical treatments (i.e. conservative treatments) have wide range of options4.

Repet­itive peripheral magnetic stimulation (RPMS) is a noninvasive technique inducing changes in neuronal excitability at the site of stimulation and at dis­tant sites, leading to pulse frequency dependent facilitation or inhibition. These effects may outlast the stimulating trains duration for minutes to even hours5.

Previously, Struppler and colleagues verified the concept of “the activation of reorganization processes in the central nervous system by inducing proprioceptive inflow by RPMS”6.

 

Aim of Work

To evaluate the pain-reducing effect of RPMS in CTS of different severity grades.

METHODS

 

This is a comparative study. We recruited 20 carpal tunnel syndrome patients (16 females and 4 males) out of the patients presented to the Clinical Neurophysiology Unit of Kasr El Aini, Cairo University Hospitals; Cairo; Egypt. All of them were naive about the repetitive magnetic stimulation procedure and gave written and oral informed consent to the study. The study has been reviewed by the appropriate ethics committee.

The study included patients with age above 20 years and below 60 years with electrophysiological proof of having carpal tunnel syndrome. While it excluded patients with history suggestive of any other neurological or chronic systemic disease; installing pacemakers or intracranial metal objects and artificial metal tooth; pregnant females or those who are not consenting for the procedures.

All participants were subjected to clinical neurological examination, nerve conduction studies, received RPMS and performed Visual Analogue –pain- Scales (VAS). They were divided at random into two groups; Patients group receiving real RPMS (therapeutic) and patients group receiving sham stimulation (placebo). Both groups received three RPMS sessions on alternative days. Evaluation of our cases before treatment reported no statistically significant difference between both groups as regards age, gender or VAS basal ratings.

Sensorimotor conduction studies for the median nerve ipsi-lateral to the upper limb pain following the guidelines for diagnosis of CTS in the unit. This was carried on a Dantec machine software version 1.6 (made in Denmark) Model (Key point).

The participants were subdivided according to the severity of the CTS into 4 subgroups: “Early CTS” with abnormal findings only on sensory conduction studies (SCS) (Peak latency > 3.5 ms, velocity <40 m/s) and\or comparative studies (difference > 0.5 ms); “Mild CTS” with abnormal SCS and prolonged distal motor latency (DML) but less than 150% of the highest normal value (5.4 ms); “Moderate CTS” with abnormal sensory conduction studies and prolonged distal motor latency but more than 150% of the highest normal value (5.4 ms); “Severe CTS” with any of the aforementioned abnormalities with evidence of axon loss as defined by either: (1) an absent sensory nerve action potential or mixed nerve action potential; (2) a low-amplitude (less than 2.5 mV) or absent thenar muscles compound motor action potential; or (3) a needle Electromyography with fibrillation potentials or neurogenic Motor Unit Potentials7.

Repetitive peripheral magnetic stimulation was carried out using Magstim rapid magnetic stimulator (Magstim Company, Whitland, Wales, United Kingdom), connected with a figure-of-eight coil with a diameter of 70 mm.

The intensity of stimulation was expressed as a percentage of the maximum output of the stimulator (0-100%) and was adjusted according to the visual resting motor threshold, defined as the lowest stimulation intensity, applied on the motor cortex, for producing a visible hand muscle contraction in at least 5 of 10 trials8. In real RPMS, the coil position was tangential to the affected wrist joint with stimulation point at mid palmer wrist, flow direction peripherally,  with power at motor threshold, 10 Hz  for 10 seconds per train with a 20 seconds inter-train interval with total of 1050 pulse/session. While in sham RPMS, the coil was angulated away from the wrist.

 

Visual Analogue –pain- Scale was measured before treatment and immediately after each of the three sessions and 4 weeks after the last session.

Statistical values were expressed as mean ± standard deviation (SD) using SPSS program version 20. These results were analyzed statistically using the independent student’s t-test. Pearson correlation coefficient (r) was used to measure correlation between quantitative variables. Paired t-test was used to compare pre and post RPMS values in normally distributed groups of data.

 

RESULTS

 

The patients group receiving real RPMS, showed highly statistical significant reduction in VAS value was observed (P-value = 0.003). The percentage of improvement was (94.5%), which indicates a significant pain reduction in the patients of this group after treatment. While among patients receiving sham RPMS treatment, no statistically significant reduction in VAS value was found (P-value=0.18). There was insignificant improvement of patients of this group after treatment. This is shown in Table (1).

Patients with early CTS showed significant reduction in their pain measured by VAS after receiving real RPMS (p-value 0.041). While patients with mild, moderate and severe CTS showed no statistically significant difference in VAS after receiving real RPMS. This is shown in Table (2).

There was no significant correlation detected between the response to RPMS treatment with age of the patients (P>0.05). As well, there was no significant correlation detected between the severity of CTS group and pain scale after RPMS treatment (P>0.05).


Table 1. Comparison between VAS before and after Real and Sham RPMS.

 

Treatment

Real RPMS (n=10)

Sham RPMS (n=10)

Mean

SD

Minimum

Maximum

Mean

SD

Minimum

Maximum

Pain scale

Pre-peripheral RPMS

63.33

9.61

50.00

80.00

56.64

6.67

48.00

70.00

Pain scale post-RPMS

47.50

6.22

40.00

60.00

55.09

8.73

38.00

70.00

P-value

0.003*

0.18

n number, RPMS repetitive magnetic stimulation; SD standard deviation.

*Significant at P<0.01

Table 2. Comparing VAS before and after real RPMS in patients with different CTS grades.

 

 

 

Mean

SD

Minimum

Maximum

P-value

Early  CTS n= 5

Pain scale before RPMS

60

9.35

50

70

0.041*

Pain scale after RPMS

45

5

40

50

Mild  CTS n=7

Pain scale before RPMS

60

10

50

70.00

0.180

Pain scale after RPMS

48.33

10.41

40

60

Moderate CTS n=4

Pain scale before RPMS

75

7.07

70

80

0.180

Pain scale after RPMS

50

0.00

50

50

Severe  CTS n=4

Pain scale before RPMS

65

7.07

60

70.00

0.157

Pain scale after RPMS

50

7.07

45

55

CTS carpal tunnel syndrome; n=number; RPMS repetitive peripheral magnetic stimulation; SD standard deviation; VAS Visual Analogue Scale.

*Significant at P<0.05

 


DISCUSSION

 

In this study that was carried out on twenty patients having electrophysiological evidence of CTS with different severity degrees, we aimed to evaluate the neuropathic pain reducing effects- measured by VAS- of RPMS targeting the wrist.

In this study, there was inevitable female predominance (16 females / 4 males). This was close to CTS female predominance 86.3% in a previous study9, 72.73% in another10 and 66.8% in an older study11.

Recent reviews did not mention about any trials for therapeutic effects of RPMS on CTS, so did our search. To our knowledge, this study is a leading study in researching the therapeutic effect of RPMS on CTS.

We found a highly statistically significant reduction of pain scale ratings immediately after the end of the sessions in the patients’ group who received real RPMS indicating the immediate analgesic effects of RPMS sessions and augmentation of these effects by repeated sessions. While patients’ group who received sham stimulation showed no statistically significant difference in their pain scale ratings. These results regarding the pain relieving effects of RPMS were supported by several studies that have tested and proved that sessions of noninvasive magnetic stimulation using the technique of RPMS could relieve chronic neuropathic pain at least transiently12,13.

There were differences in the timing of pain evaluation ranging from a few minutes14-16 to several days after repetitive trans magnetic stimulation (rTMS) session12, and the absence of double-blind active versus sham (placebo) stimulation may have also contributed to the results changeability.

High frequency of 10 Hz RPMS was used in this study which is in agreement with many studies that have been performed at higher frequencies. Lefaucheur and colleagues demonstrated that rTMS was able to relieve neuropathic pain when administered over M1 10 Hz but not at 0.5 Hz12. Another showed that rTMS provided better alleviation of pain at 20 Hz than at 1 Hz17. A third group found that 10 Hz rTMS was more efficacious than 5 Hz rTMS, whereas 1 Hz rTMS did not produce significant effects18.

As low and high frequencies have opposite effects on cortical excitability, the mechanisms of the analgesic effects are likely produced by the stimulation of superficial fibers, tangential to the surface of the precentral gyrus19. However, analgesic effects were obtained whatever the origin of pain, including the post stroke pain (mainly thalamic stroke) and facial pain caused by trigeminal neuropathy12, as well as other causes of neuropathic pain, such as spinal cord injury, root or brachial plexus avulsion, or peripheral nerve trunk lesion20.

An earlier RPMS study was carried out on patients with traumatic brachial plexopathy and showed its modulation of corticospinal tract excitabil­ity and the pain scale. In that study, the Trapezius muscle was targeted5. The study concluded that RPMS for 10 sessions may have positive therapeutic effects on motor recovery and pain relief in patients with traumatic brachial plexopathy. Therefore, it is a useful adjuvant in the therapy of these patients. This is in concordance to our RPMS results showing the gradual and increasing improvement of pain as reflected by the gradual significant decline in pain scales ratings after each session that reached its maximal improvement after the last session.

However, no further peripheral sites were studied, again to our knowledge, until the current time.

In light of the findings yielded from this study, we can conclude that high-frequency RPMS over the wrist is effective in improving pain in patients with CTS. So it can be suggested as a new treatment option for patients with CTS to improve quality of life in such patients.

In our study, only early CTS benefited from real RPMS pain reducing effect. Patients receiving sham RPMS did not show such result, minimizing the possibility of the theory of “a placebo effect”. As mentioned recently, non-surgical treatments are recommended for patients with mild symptoms of CTS4. Our study suggests that high frequency RPMS could be added in the near future to the “CTS non-surgical treatment” list. However; the mechanism of pain reduction whether peripheral or central was not concluded.

We are recommending replication of this study on larger sample size and longer follow up period to fairer judgment of reliability of RPMS therapeutic effects in CTS. We are even recommending post RPMS evaluation of the patients via NCS and functional brain imaging in addition to pain scales. This would provide objective proof of the occurring improvement and its mechanism. Moreover; trying RPMS in treatment of other diseases with neuropathic pains, increasing number of sessions of RPMS as well as using low frequency of RPMS.

 

[Disclosure: Authors report no conflict of interest]

 

REFERENCES

 

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2.      L'Heureux-Lebeau B1, Odobescu A, Moser T, Harris PG, Danino MA. Ulnar subluxation of the median nerve following carpal tunnel release: a case report. J Plast Reconstr Aesthet Surg. 2012 Apr;65(4):e99-101.

3.      El Bardawil MM, Younis GA,  Hassan MM, Mohammed ER. A study of retrograde degeneration of median nerve forearm segment in carpal tunnel syndrome of variable severities. Alex J Med. 2014 Dec;50(4): 323-31.

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14.    Migita K, Uozumi T, Arita K, Monden S. Transcranial magnetic coil stimulation of motor cortex in patients with central pain. Neurosurgery. 1995, 36:1037-40.

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الملخص العربي

 

الدور العلاجي للتنبيه المغناطيسي المتكرر الطرفي في متلازمة النفق الرسغي

 

تعد متلازمة النفق الرسغي إحدى أشهر أسباب الألم العصبي في الطرف العلوي ويميل هذا الألم للزيادة مع تقدم مراحل المرض مما قد يؤثر على الأداء الحركي والأنشطة اليومية المختلفة، لذا يجب أن يتم تطبيق العلاج المناسب مع بداية الأعراض، هذا وقد تم بحث الكثير من البدائل العلاجية التحفظية لمتلازمة النفق الرسغي إلا أن البدائل لم تتضمن التنبيه المغناطيسي المتكرر الطرفي. 

وقد هدفت الدراسة إلى تقييم الآثار العلاجية للتنبيه المغناطيسي المتكرر الطرفي في متلازمة النفق الرسغي، وتمت بإجراء رسم الأعصاب ومقياس الألم بالمضاهاة البصرية والتنبيه المغناطيسي المتكرر الطرفي لعشرين مريض يعانون من متلازمة النفق الرسغي.

وقد وجد تضاؤل ملموس للألم بين مرضى متلازمة النفق الرسغي ذو الدرجة المبكرة لمدة تصل إلى شهر بعد التنبيه المغناطيسي المتكرر الطرفي مما أدى إلى استنتاج إمكانية اعتبار التنبيه المغناطيسي المتكرر الطرفي أحد الأدوات الغير جائرة لتخفيف الألم الناتج عن متلازمة النفق الرسغي في مراحله الأولية.



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