Application of Repetitive Transcranial Magnetic Stimulation in Neuropathic Pain: A Narrative Review

Abstract

Neuropathic pain, affecting 6.9–10% of the general population, has a negative impact on patients’ quality of life and potentially leads to functional impairment and disability. Repetitive transcranial magnetic stimulation (rTMS)—a safe, indirect and non-invasive technique—has been increasingly applied for treating neuropathic pain. The mechanism underlying rTMS is not yet well understood, and the analgesic effects of rTMS have been inconsistent with respect to different settings/parameters, causing insufficient evidence to determine its efficacy in patients with neuropathic pain. This narrative review aimed to provide an up-to-date overview of rTMS for treating neuropathic pain as well as to summarize the treatment protocols and related adverse effects from existing clinical trials. Current evidence supports the use of 10 Hz HF-rTMS of the primary motor cortex to reduce neuropathic pain, especially in patients with spinal cord injury, diabetic neuropathy and post-herpetic neuralgia. However, the lack of standardized protocols impedes the universal use of rTMS for neuropathic pain. rTMS was hypothesized to achieve analgesic effects by upregulating the pain threshold, inhibiting pain impulse, modulating the brain cortex, altering imbalanced functional connectivity, regulating neurotrophin and increasing endogenous opioid and anti-inflammatory cytokines. Further studies are warranted to explore the differences in the parameters/settings of rTMS for treating neuropathic pain due to different disease types.

Transcranial Magnetic Stimulation to Treat Neuropathic Pain: A Bibliometric Analysis

“…It may also be important to investigate the mechanisms underlying the TMS interventions in neuropathic pain, even using translational approaches. TMS is already recommended for the treatment of resistant psychiatric pathology, namely depression disorder [ 39 ] or obsessive-compulsive disorder [ 40 ], but the mechanisms behind TMS and neuropathic pain complexity rise specific challenges that are not fully understood [ 24 ], and clinical studies may be considered heterogeneous [ 41 ]. In fact, a main problem in the use of repetitive TMS for a therapeutic purpose in chronic pain patients is the heterogeneity of the proposed protocols, particularly in terms of the definition of the stimulation target and session rhythm.…”

Non-Invasive Electric and Magnetic Brain Stimulation for the Treatment of Fibromyalgia

“…Although non-invasive brain stimulation appears to be effective for the treatment of fibromyalgia, rTMS and tDCS effects might not be specific to the symptoms of this pathology. Thus, rTMS protocols described in clinical fibromyalgia studies have shown similar effectiveness for relieving rheumatic [ 101 , 102 ] and post-stroke [ 103 ] pain. Likewise, the therapeutic effects of electric brain stimulation also do not seem to be restricted to fibromyalgia, as pain improvements after tDCS interventions have been described in patients with different pain syndromes (trigeminal neuralgia, poststroke pain syndrome, back pain, and fibromyalgia) [ 104 ].…”

Effects of different transcranial magnetic stimulations on neuropathic pain after spinal cord injury

“…Repetitive transcranial magnetic stimulation (rTMS) as a non-invasive, promising cortical stimulation technique has been suggested to be more effective in the treatment of neuropathic pain of central origin ( 7 , 8 ). Therefore, there is substantial evidence showed effective pain management when applying rTMS to the primary motor cortex (M1) ( 5 , 9 , 10 ). There are several parameters associated with the effectiveness of rTMS like stimulation site, field orientation, frequency, intensity, and duration of stimulation ( 11 ).…”