Effects of Repetitive Transcranial Magnetic Stimulation in the Treatment of Phantom Limb Pain in Landmine Victims: ANTARES
Effects of Repetitive Transcranial Magnetic Stimulation in the Treatment of Phantom Limb Pain in Landmine Victims: ANTARES
Phantom Limb Pain (PLP) is a neuropathic chronic syndrome, characterized by a painful
 sensation in a body part that has been amputated. The incidence of phantom limb pain is
 between 50-80% of all amputees, however, additional risk factors as psychological trauma,
 blood loss, and infection increases its incidence after a traumatic amputation in landmine
 victims. Satisfactory management is often difficult to achieve and different clinical trials
 with medical and surgical measures have yielded unsatisfactory results. The response rate
 with pharmacologic treatment is around 30% using conventional medication as opiates and
 N-methyl-D-aspartate (NMDA) receptor antagonists, which is not significantly different from
 response rates with placebo.

 Recent case series have shown that repetitive Transcranial Magnetic Stimulation (rTMS) of the
 motor cortex can display an effectiveness that goes from 52% to 88% in the treatment of some
 refractory neurogenic pain cases which is quite superior to conventional management. However,
 the use of this type of treatment has not been studied in patients with phantom limb pain
 secondary to landmine injuries. The main objective of this trial is to evaluate the efficacy
 and safety of rTMS in the treatment of phantom limb pain in landmine victims.

 A double blind randomized placebo-controlled clinical trial, including 54 landmine victims
 with PLP will be performed. At the time of enrollment, a complete medical evaluation will be
 performed and those patients who meet the inclusion criteria will be randomly assigned to one
 of two groups, to receive rTMS in series of 20 trains of 6 s in duration (54-s intertrain
 interval) at a stimulation rate of 10 Hz (1200 pulses) and an intensity of 90% rest motor
 threshold using an "active" coil or a "sham" coil. Sessions will be administered 5 days a
 week (Monday to Friday) during two consecutive weeks. The stimulation will be directed to the
 primary motor cortex contralateral to the amputated limb. Response will be evaluated by
 measuring the pain intensity at baseline and after each session using a visual analog scale.
 These measurements will be repeated 2 weeks after the end of the treatment scheme, in order
 to determine the duration of the analgesic effect of rTMS
Background In 2007 Colombia was one of the five countries in the world with the highest
 number of anti-personnel landmine victims [1]. These are small devices designed to injure or
 kill people and animals by exploding when a minimum pressure is exerted on them
 (approximately 6 Force-Kg) [2]. Between 1999 and 2008 there were 6696 reported incidents with
 these artifacts in Colombia, partly due to an intensified civil war conflict in this period
 of time, however, it is estimated that the number of affected subjects might be higher due to
 underreporting [1]. This problem has had an enormous impact on Public Health in Colombia,
 aggravated by the fact that victims, often children or young adults, frequently suffer
 significant degrees of physical and psychological disabilities, leading to an increase in the
 number of healthy life years (DALYs) lost in our population, together with important
 secondary economic impacts [1-5]. Anderson et al [3] estimated that the quality of life is
 affected in 25 to 87% of families with a relative victim of a landmine.

 Among the multiple physical and psychological disabilities and sequels derived from landmines
 [6-8], one of the most important consequences is the chronic neuropathic pain secondary to
 amputation. Ketz conducted a retrospective study among 30 soldiers wounded in combat, finding
 a prevalence of 77% of Phantom Limb Pain (PLP) after traumatic amputation [9]. The factors
 associated with development of neuropathic pain in these patients include central and
 peripheral phenomena [10-12]. The direct damage to the involved tissue produces inflammation,
 and in some cases infection which induces the release of several molecules, such as hydrogen,
 potassium and arachidonic acid, which in turn, activate and sensitize pain receptors, leading
 to exaggerated responses to any minimal painful stimuli [11]. Another proposed mechanism for
 the development of PLP is the fact that damaged peripheral nerve tissues grows into so-called
 "neuromas" [13, 14]. These have shown to express a greater density of sodium channels in
 their cell membranes, increasing the activity of peripheral nociceptors [15]. This increased
 activity leads to changes in the synaptic structure of neurons located in the dorsal horn of
 the spinal cord, increasing their excitability as well as reducing the frequency and
 intensity of their inhibitory processes [11, 16]. Besides spinal and peripheral changes,
 encephalic alterations have also been found [17-24]. Melzack introduced the neuromatrix
 theory, which suggested that pain is a multidimensional experience, which involves a large
 neural network that enables the integration and simultaneous processing of information from
 multiple peripheral receptors with the processed information permanently in these neural
 circuits, emphasizing the importance of central structures in all aspects of pain [25]. In
 addition, Merzenich et al [26] conducted a study in adult monkeys, finding that after
 amputation of a limb, the primary somatosensory cortex seems to rearrange itself in the
 cortical areas representing the amputated limb.

 The high prevalence of PLP after amputation has led to major efforts in order to lessen the
 pain in affected patients. However, results using conventional medical treatment, including
 opiates, N-methyl-D-aspartate (NMDA) receptor antagonists and surgery, are poor, with an
 general efficacy rate of about 30%, not statistically better than placebo [20, 27-33].
 Recently, it has been proposed that repetitive Transcranial Magnetic Stimulation (rTMS) can
 be an effective alternative in the treatment of neuropathic pain [34].

 The rTMS is a non-invasive stimulation technique of the human brain that generates a small
 magnetic field of high intensity through a brief electrical current generated by a magnetic
 coil placed over the head of the individual [35, 36]. The electric currents induced in the
 cerebral cortex run in a parallel plane to the plane of the stimulation, in such a way that
 this stimulation affects mainly those brain elements of the cerebral cortex activating the
 pyramidal cells transinaptically (37). The use of high frequency rTMS (> 1Hz) raises the
 blood flow in the stimulated area, inducing an increased brain activity. On the other hand,
 low-frequency stimulation (<1 Hz) reduces brain activity [38, 39]. In addition to vascular
 changes, the rTMS may induce modifications in several hormonal axes and even in the
 production of neurotransmitters, such as dopamine serotonin, arginine, NMDA, taurine and
 aspartate [40-43]. Additionally it was found that rTMS may regulate the expression of some
 genes including c-fos and c-jun, which are vital structural components of the activator
 protein 1, a special transcription factor that helps to regulate cellular processes including
 differentiation, proliferation and apoptosis. The rTMS also helps to modulate some peptide
 biosynthetic pathways, such as brain-derived neurotrophic factor (BDNF) and glial fibrillary
 acidic protein (GFAP), important molecules for neuronal plasticity processes [42-44]. Using
 functional Magnetic Resonance Imaging (fMRI), Li et al [45], observed that stimulation with
 1Hz rTMS on the left dorsolateral prefrontal cortex induced an immediate increase in the
 local blood flow, followed by perfusion of the bilateral middle prefrontal cortex, right
 orbital frontal cortex, left hippocampus, middorsal nucleus of the thalamus, bilateral
 putamen, pulvinar and insula. These previous observations suggest that in addition to
 producing local changes in the stimulated cerebral cortex, rTMS might also influence the
 activity of other cortical and sub-cortical regions through different brain circuits and
 connections [46, 47].

 Reported side effects of rTMS are minor events, mainly related with cephalagia, changes in
 the stimulation threshold of hearing, tinnitus, local erythema, syncopal episodes and in some
 cases mild and transient cognitive disorders related to the area stimulated [48-51]. The most
 important complication described has been possible induction of seizures (<0.1%); however
 these seizures have not been associated with sequels or with development of epilepsy [52-54].
 There are some medical and non-medical contraindications to its use, such as, the presence of
 metal endo-cranial, cardiac pacemakers or hearing, as well as cardiac arrhythmias,
 intracranial hypertension, use of medications that lower the seizures threshold and personal
 or family history of epilepsy [55].

 The rTMS was first used on small groups of patients suffering of chronic neuropathic pain
 secondary to trigeminal neuralgia or brachial plexus injury [56-58]. Lefaucheur et al [56]
 conducted a study in 18 patients with an average age of 54 years, presenting chronic
 neuropathic pain of one hand, resistant to drug treatment. The patients were randomized for
 three twenty minute sessions of rTMS, one with a low frequency (0.5 Hz) magnetic stimulation,
 other with high frequency (10 Hz) and the other with sham coil to evaluate the placebo
 effect. The level of pain before and after each session was evaluated by using the Visual
 Analog Scale (VAS). In this study it was determined that patients undergoing a 10-Hz rTMS
 perceived a more significant reduction of the pain compared with subjects who received a
 stimulation with 0.5 Hz rTMS or with those who only received placebo treatment. Subsequently,
 Lefaucheur et al [57] replicated these results in a group of 60 patients with neuropathic
 pain secondary to thalamic infarction, brachial plexus injury or trigeminal nerve injury, who
 underwent two sessions of high frequency rTMS separated by three weeks, concluding that 65%
 of the patients reported some improvement of their symptoms. The same author conducted a
 study that included 36 patients with neuropathic pain secondary to either brachial plexus or
 trigeminal nerve injuries. All of them received high frequency rTMS. The first one during two
 sessions and the latter received three sessions. As in the previous studies the level of pain
 was evaluated, before each session and one week after, using the VAS. The best response to
 pain was obtained between the second and fourth day after the initial treatment and this
 improvement was maintained for a period of seven days [59].

 Objectives

 General Objective To evaluate the effectiveness of rTMS for the treatment of phantom limb
 pain in victims of anti-personnel landmines.

 Specific Objectives

 1. To determine the intensity and duration of the analgesic effects of rTMS in patients
 victims of landmines with PLP.

 2. To identify the characteristics of victims of landmines with PLP associated with a
 greater response to rTMS.

 3. To identify adverse events associated with the application of rTMS in victims of
 anti-personnel landmines with PLP.

 Study Design Double blind, randomized, placebo controlled clinical trial.

 Sample size The sample size was calculated according to the arc cosine formula considering a
 power of 80% and a type I error of 0.05, assigning a successful rate of 20% in the control
 group and 60% in the active group. After adjusting for a loss rate of 5%, the total number of
 patients to be recruited was 54 (27 patients per group).

 Population The population will be composed of patients victims of anti-personnel landmines,
 who have had one of their lower limbs amputated and display classical symptoms of PLP. The
 patients will be recruited from the physical rehabilitation service at the Hospital
 Universitario de Santander (HUS), Bucaramanga, Colombia and local Non-Governmental
 Organizations (NGOs). Those who consent to participate, fulfill screening criteria and don't
 present any exclusion criteria will be included in the study.

 Inclusion criteria

 1. Men and women 18 years or older.

 2. Amputation at any level of one lower limb by anti-personnel landmines.

 3. Symptoms compatible with PLP, defined as painful sensation, sensation of shooting,
 stabbing, boring, squeezing, throbbing and burning or paresthesia or any other pain
 sensation in a limb that doesn't exist anymore.

 Exclusion criteria

 1. Diagnosis of complex regional pain syndrome.

 2. Any pathology that based on the judgment of the researcher that could alter the course
 of PLP (neoplasias, immunological disorders, etc.)

 3. Previous diagnosis of cancer.

 4. Renal insufficiency requiring dialysis treatment.

 5. Pregnancy

 6. History of epilepsy.

 7. Cardiac arrhythmias.

 8. Metallic prostheses in the skull.

 9. History of severe head trauma.

 10. Use of tricyclic antidepressants (amitriptyline, imipramine, clomipramine).

 11. Use of antipsychotic medication (chlorpromazine, levomepromazine, haloperidol,
 clozapine, olanzapine, etc.).

 12. Mentally or neurologically disabled patients that are considered not fit to approve
 their participation in the study.

 Study development

 Logistic phase

 This phase will include the following activities:

 1. Acquisition of the materials required for the development of the project.

 2. Elaboration of flyers, promotional and educative material, manual of procedures and Case
 Report Format (CRF).

 4. Training of personnel that will participate in the study 5. Randomization of treatment
 Randomization of the treatment will be performed by an epidemiologist of the Fundación
 Cardiovascular de Colombia (FCV). It will be done in blocks, in order to avoid long sequences
 of patients assigned to the same group and to reduce some of the bias inherent to the simple
 randomization process.

 Recruitment Phase Patients will attend the screening visit at the FCV or at offices of the
 physicians involved in the study.

 Screening Visit During this visit a complete medical check-up, based on universally accepted
 techniques, will evaluate neuropathic compromise, medications and other therapies used for
 the treatment of PLP. The inclusion/exclusion criteria will be applied by a neurologist and
 the selected candidates will be informed about the study. It will be asked to patients to
 avoid consumption of new analgesic medications during the study development. If one patient
 requires the introduction of a new analgesic treatment for increased pain or concept of the
 physician, this will be recorded and taken into consideration in the data analysis.

 Initial and Follow-up Visits The selected patients will be scheduled for the initial visit.
 In this visit, information about the patient's medical history, educational level,
 socioeconomic status and general condition will be collected by a physician. In addition, a
 physical therapist will perform a baseline assessment of neuropathic pain using a VAS. Each
 patient will be randomized to receive rTMS, using a biphasic pulse stimulator (Magstim
 Company Ltd, Whitland, UK), in series of 20 trains of 6 s in duration (54-s intertrain
 interval) at a stimulation rate of 10 Hz (1200 pulses) at an intensity of 90% rest motor
 threshold using an "active" coil or a "sham" coil. Sessions will be administered five days a
 week during two consecutive weeks. The stimulation will be directed to the primary motor
 cortex contralateral to the amputated limb.

 Clinical evaluators and those responsible for applying the pain evaluation scales will be
 blind to the assigned group. The rTMS will be performed by a non-blinded member of the
 research group. The patients included in the study should not have prior knowledge of the
 technical details of rTMS.

 Response will be evaluated by measuring the pain intensity at baseline and after each session
 using a VAS. These measurements will be repeated 2 weeks after the ending of the treatment
 scheme, in order to determine the duration of the analgesic effect of rTMS.

 Data base depuration phase Each patient will be identified using an internal code. The study
 coordinator will monitor the proper collection of data, taking into account that the
 information contained on the forms is complete and accurate. Also, he/she will keep a record
 of the visits performed during the study and verify that the data collection is performed in
 a timely manner.

 After completing all the data entry to the CRF the results will be audited and the detected
 errors evaluated and corrected. The information will be entered in two different databases by
 two different people and the records compared to detect any discrepancy. The mistakes will be
 corrected according to the CRF, and the corrections registered.

 Statistical analysis For the statistical analysis, Stata 11.0 (StataCorp, College Station,
 TX, USA) will be used. The descriptive analysis will be composed of medians and proportions
 according to the nature of the variables, with their respective 95% confidence intervals. As
 a dispersion measurement the Standard Deviation will be calculated. The distribution of the
 variables will be studied using the Shapiro-Wilk test and the homoscedasticity of the
 variances with the Levene test. To detect any difference between the groups, a T-test or a
 Mann Whitney test will be performed according to the distribution of the variables. The
 categorical variables will be compared using the Chi Squared test or the exact Fisher's test.
 If required, a multiple logistic regression or a covariance analysis will be performed.

 Endpoints

 At the end of the treatment the following endpoints will be evaluated:

 1. Percentage reduction in the intensity of neuropathic pain.

 2. Presence of adverse events related to the administration of rTMS.

 Final Report The results of the study will be evaluated and discussed and a final report
 presented to the Colombian Administrative Department of Science, Technology and Innovation
 (COLCIENCIAS), entity that is sponsoring the project. The results will be submitted for
 publication and presented in scientific meetings.

 Ethical aspects This study will be conducted in accordance with the Declaration of Helsinki
 and the Colombian legislation, following the Ministry Of Health resolution No. 8430/93. Prior
 to the admission of the patients in the study, the objectives and the methodology will be
 explained and a written informed consent obtained. The present study has been approved by the
 Research Ethics Committee of the FCV (Act # 197/June 19/2009). The patients' right to
 confidentiality will be kept in all the phases of the study.

 Evaluation and management of adverse events

 During the visits the patients will be asked about the presence of any adverse events. These
 will be classified by the physician as serious or non-serious adverse events. A serious
 adverse event should meet one or more of the following criteria:

 1. Death

 2. Life-threatening

 3. Hospitalization or prolongation of a current hospital stay

 4. Persistent or significant disability

 The presence of a serious adverse event that represents any hazard for the patient and/or
 requires immediate medical or surgical intervention will force the discontinuation of the
 treatment and initiation of pertinent medical management. The research staff will notify the
 Adverse Event Committee (AEC) of the FCV of any serious adverse event within 24 hours of its
 documentation.

 A non-serious adverse event will be classified as following:

 1. Mild: The patient is aware of his/her symptoms, but those are tolerable. Medical
 intervention or specific treatment is not required.

 2. Moderate: The patient presents troubles that interfere with his/her daily activity.
 Medical intervention or specific treatment is required.

 3. Severe: The patient is unable to work or attend his/her daily activities. Medical
 intervention or specific treatment is required.

 The possible relationship between the adverse events and the tested medication will be
 classified by the research staff on the basis of his/her clinical judgment and the following
 definitions:

 1. Definitely related: The event can be fully explained by the administration of the tested
 medication.

 2. Probably related: The event is most likely to be explained by the administration of the
 tested medication, rather than other medications or the patient's condition.

 3. Possibly related: The event may be explained by the administration of the tested
 medication or other medications, as well as the patient's condition.

 4. Not related: The event is most likely to be explained by either the patient's condition
 or the use of other medications, rather than the one tested.

 All events will be reported to the AEC. Although the project has been designed to minimize
 the inherent risks, any adverse event related to the study procedures will be carefully
 evaluated by the AEC and the costs generated by its treatment covered by the study's
 administration.

 Acknowledgements This study is supported by a grant from the Colombian Administrative
 Department of Science, Technology and Innovation (COLCIENCIAS) (Project N. 656649326169).

 Competing interests The author(s) declare that they have no competing interests.
Inclusion Criteria:

 -  Men and women 18 years or older

 -  Amputation at any level of one lower limb by anti-personnel land mines

 -  Symptoms compatible with PLP, defined as painful sensation, sensation of shooting,
 stabbing, boring, boring, sqeezing, throbbing and burning or paresthesia or any other
 pain sensation in a limb that doesn't exist anymore.

 -  Willingness to participate in the study and to sign the informed consent form.

 Exclusion Criteria:

 -  Diagnosis of complex regional pain syndrome.

 -  Any pathology that based on the judgment of the researcher that could alter the course
 of PLP (neoplasias, immunological disorders, etc.)

 -  Previous diagnosis of cancer.

 -  Renal insufficiency requiring dialysis treatment.

 -  Pregnancy

 -  History of epilepsy.

 -  Cardiac arrhythmias.

 -  Metallic prostheses in the skull.

 -  History of severe head trauma.

 -  Use of tricyclic antidepressants (amitriptyline, imipramine, clomipramine).

 -  Use of antipsychotic medication (chlorpromazine, levomepromazine, haloperidol,
 clozapine, olanzapine, etc.).

 -  Mentally or neurologically disabled patients that are considered not fit to approve
 their participation in the study.