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Mechanisms and therapeutic applications of electromagnetic therapy in Parkinson’s disease
Transcranial magnetic stimulation in Parkinson’s disease
For example, biomagnetic measurements performed using magnetoencephalography (MEG) in 30 patients affected by idiopathic PD exposed to TMS evidenced that 60% of patients did not exhibit tremor, muscular ache or dyskinesias for at least 1 year after TMS therapy [58].
High-frequency transcranial magnetic stimulation in Parkinson’s disease
In the first PD patients treated with high-frequency TMS in 1993, motor symptoms, tremor, rigidity and akinesia improved significantly allowing to decrease the administration of l-dopa by a mean of 55% [99]. Since then, several thousands of patients worldwide have been fitted with high-frequency TMS implants achieving marked improvements in their symptoms, making this method the reference procedure for advanced PD [100].
The time course of improvement following high-frequency TMS treatment differs for different cardinal symptoms of PD [101]. For instance, rigidity and resting tremor decrease immediately, within a few seconds after high-frequency TMS [102]
Pulsed electromagnetic field therapy in Parkinson’s disease
In October 2008 the Food and Drug Administration approved the use of PEMF therapy for treatment of major depressive disorder in PD patients who failed to achieve satisfactory improvement from very high dosages of antidepressant medications [133, 134]. Several studies reported PEMF therapy improved cognitive functions and motor symptoms. For example, an investigation involving three elderly PD patients with cognitive impairment assessed the effect of PEMF therapy on macrosomatognosia, a disorder of the body image in which the patient perceives a part or parts of his body as disproportionately large [135]. After receiving PEMF therapy, PD patients’ drawings showed reversal of macrosomatognosia (assessed by Draw-a-Person test) with reduction of the right parietal lobe dysfunction. Furthermore, PEMF therapy applied to a 49-year-old male PD patient with stage 3 disease, as assessed by Hoehn and Yahr scale, resulted in a marked improvement in motor and non-motor symptoms such as mood swings, sleeplessness, pain and sexual and cognitive dysfunctions, suggesting that PEMF therapy should be tested in large cohorts of PD patients as monotherapy and should also be considered as a treatment modality for de novo diagnosed PD patients [136]. PEMF therapy was also effective in improving visuospatial deficits in four PD patients, as assessed by the clock-drawing test [137]. Moreover, PEMF therapy improved PD-associated freezing (a symptom manifesting as a sudden attack of immobility usually experienced during walking) in 3 PD patients through the facilitation of serotonin neurotransmission at both junctional and non-junctional neuronal target sites [127].
For example, stimulation of the ventral intermediate nucleus of the thalamus can dramatically relieve PD-associated tremor [104]. Similarly, stimulation of the STN or globus pallidus interna (GPi) can substantially reduce rigidity, tremor, and gait difficulties in patients affected by idiopathic PD [105]. Stimulation of the GPi also reduces all of the major PD motor manifestations, including the reduction of l-dopa-induced dyskinesias and involuntary movements produced by individual doses of dopaminergic medications that can limit treatment efficacy [106
Transcranial magnetic stimulation in Parkinson’s disease
s the use of six groups of electromagnetic fields as previously described [42, 43] and summarized below:
Static/permanent magnetic fields can be created by various permanent magnets as well as by passing direct current through a coil.
Transcranial magnetic stimulation (TMS) utilizes frequencies in the range 1–200 Hz.
Low-frequency electromagnetic fields mostly utilize 60 Hz (in the US and Canada) and 50 Hz (in Europe and Asia) frequencies in distribution lines.
Pulsed radio frequency fields utilize frequencies in the range 12–42 MHz.
Millimeter waves refer to very high-frequency in the range 30–100 GHz.
Pulsed electromagnetic fields (PEMFs) utilize frequencies in the range 5–300 Hz with very specific shapes and amplitudes.
Electromagnetic therapy is defined as the use of time-varying electromagnetic fields of low-frequency values (3 Hz–3 kHz) that can induce a sufficiently strong current to stimulate living tissue [44]. Electromagnetic fields can penetrate all tissues including the epidermis, dermis, and subcutaneous tissue, as well as tendons, muscles and bones [45]. The amount of electromagnetic energy used and its effect on the target organ depends on the size, strength and duration of treatment [44]. Electromagnetic fields can be divided into two categories: static and time-varying. Electromagnetic therapy falls into two categories: (1) hospital use which includes TMS, repetitive transcranial magnetic stimulation (rTMS) and high-frequency TMS and (2) home use including PEMF therapy.
Pulsed electromagnetic fields
PEMF therapy improves PD symptoms including tremor, slowness of movement and difficulty in walking [159]. It is non-invasive, safe and improves PD patients’ quality of life [124, 160]. PEMF therapy, employed for PD treatment, supports the body’s own healing process for 4–6 h after therapy session [161–163]. It can be used at home and applied to the entire body or locally to target a specific body area and, if compared with dopaminergic systemic therapy, e.g. l-dopa, it can offer an alternative treatment avoiding systemic side effects such as hepatotoxicity and nephrotoxicity.
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Conclusions
Electromagnetic therapy opens a new avenue for PD treatment. Each electromagnetic therapy technique described in this review can be applied according to a single protocol or as a combination of different protocols specifically tailored to the PD patient’s needs. Beyond the necessity to choose coil or electrode size and placement, there is a variety of parameters that have to be taken into account when designing electromagnetic therapy approaches and they include stimulation intensity, duration, frequency, pattern, electrode polarity and size. Furthermore, electromagnetic therapy can also be combined with pharmacological or non-pharmacological treatments, e.g. physical therapy and cognitive tasks, to produce additive or potentiated clinical effects. In conclusion, electromagnetic therapy represents a non-invasive, safe and promising approach that can be used alone or combined with conventional therapies for the challenging treatment of PD motor and non-motor symptoms.
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Authors’ contributions
Photomodulation - which device would you choose?
