Preventing Chronification of Phantom Limb Pain Through Mirror Therapy in Conjunction With tDCS

Condition(s) studied

Investigational drug(s) / intervention(s)

Trans Direct-Cranial Stimulation (tDCS): The tDCS electrodes will be inserted into 5×7 cm (35 cm2) sponges soaked with saline (0.9 M) and placed as follows: anode over the M1 contralateral to the amputated limb (adjusted based on lower/upper amputation), and cathode over the forehead, contralateral to the anode (ipsilateral to amputated limb). Total stimulation duration will be 20 min, with a rise and decline time of 30 sec and stimulus intensity of 1.5 mA for the real tDCS real. The intensity of 1.5 mA is in the midrange of recommended intensities (1-2 mA) and supports successful blinding. The sham tDCS will be identical to the real tDCS, except no current will be applied. However, as recommended, during the first and last 30 sec, the current will be ramped up to 1.5 mA and immediately back to 0 to induce scalp sensations similar to those in real tDCS, further supporting blinding. The Mini-CT tDCS Stimulator device has been developed for home use and allows double-blind administration.

Mirror therapy: Participants will be seated with a portable mirror between their limbs so that the unaffected limb is reflected in the mirror. The participants will focus their attention on the reflection in the mirror and perform the following movements: plantarflexion and dorsiflexion and inversion and eversion of the foot, flexion and extension of the wrist and ulnar and radial deviation, for lower and upper limp amputates, respectively. The participants will continue performing the 2 sets of movements for 20 minutes (with short intermissions if needed)

Study summary

Background: Most amputees experience phantom limb pain (PLP), for years after amputation. Virtually all PLP research to date has focused on the mechanisms of chronic PLP, ignoring the mechanisms of chronification. This research project will focus on combined neuromodulatory interventions of mirror therapy (MT) and trans direct-cranial stimulation (tDCS), applied for the first time at the acute state of PLP, with an aim to prevent its chronification and chronicity. In PLP, maladaptive plasticity associated with sensory deafferentation following an amputation is one of the contributors for excessive pain.

MT is a well-accepted yet limited option, which is thought to counterbalance abnormal plasticity. tDCS is an emerging approach believed to affect the membrane potential and activity threshold of cortical neurons. tDCS analgesic effectiveness, however, is mild and short, rendering it a noneffective stand-alone treatment. The researchers' objectives are to investigate whether the combined therapy of MT and tDCS will prevent chronic PLP and improve its related clinical characteristics. In addition, the researchers will investigate the behavioral manifestations effects of the combined treatment. The investigators expect that the combined treatment applied at the acute stage of PLP will have synergistic effects on PLP intensity and thus avert its chronification. In addition, it will reduce phantom sensations, and negative affect, and will improve the sense of body ownership and agency and endogenous inhibition efficiency.

Research design: This randomized-controlled double-blinded study will be held at Israel's 3 largest rehabilitation centers. The study consists of 3 randomized patient arms (36 in each): (1) no-intervention, natural-course group; (2) MT + sham tDCS; (3) MT + real tDCS.

MT and tDCS neuromodulatory interferences will be self-administered and consist of 20 sessions, completed during 4 weeks. The researchers outcome measures include: primary outcome: pain intensity, network-related behavioral markers, and amputation-related clinical characteristics. The data gathered will be collected at 5 timepoints.

Research novelty and innovation: The researchers proposed model will provide insights on the prevention of PLP and, potentially, other neurological pathologies involving the dysfunction of sensory systems and integration and body perception.

Eligibility

Primary outcome measure(s)

• A 0-100 VAS of mean pain intensity during one week — Pain will be compared between baseline and 4 weeks after the end of the 4 weeks intervention (meaning, comparing baseline to timepoint number 3, which is exactly 8 weeks from the end of the baseline week)
  completed during 7 days, will be used to capture the weekly average of pain intensity (0 = no pain to 100 = the worst imaginable pain, via pain diary). This data will be used either in its raw, continuous form or as a transformed dichotomous variable, yes/no chronic PLP. A cutoff value of PLP intensity ≤20/100 will be used, because from a clinical perspective, pain intensity ≤20 is considered low and will seldom prompt a request for analgesic treatment.

Trial sites (3)

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