P-27: Repetitive transcranial magnetic stimulation for chronic central neuropathic pain: a scoping review
Mr. Maxwell Ng
Mei Lin Chen*,
Michael G. DeGroote School of Medicine
Topic: Health Technology Assessment
Chronic central neuropathic pain (CCNP) is a subtype of pain that arises due to damage to the central nervous system (CNS). CCNP has a multitude of causes, from acute injuries such as strokes or spinal cord injuries, to progressive disorders such as multiple sclerosis and Parkinson disease. Approximately 8% of the population may suffer from neuropathic pain, with 20-25% being chronic. Despite this significant prevalence, pharmacotherapy for CCNP can be insufficient for treating patients. As an alternative form of treatment, non-invasive brain stimulation (e.g. repetitive transcranial magnetic stimulation (rTMS)) has been increasingly proposed and utilized in healthcare, which has demonstrated evidence in managing CCNP. An overview of existing evidence is required to inform and support further research in this area.
To review the breadth and depth of peer-reviewed literature that has examined or evaluated the application of non-invasive brain stimulation techniques to CCNP.
The following databases were searched systematically for research involving non-invasive brain stimulation interventions for the management of chronic central neuropathic pain: PubMed, EMBASE, Cumulative Index for Nursing and Allied Health Literature (CINAHL), Institute of Electrical and Electronic Engineers (IEEE), Association of Computing Machinery (ACM), Scopus. Quantitative analysis of the interventions included data on intervention type(s) and the intervention characteristics (e.g. intensity, number of pulses, wave frequency). Qualitative analysis of the interventions included data on site of stimulation and key findings.
Preliminary results show that rTMS holds strong potential to be used as a treatment for CCNP. The clinical effects are modest and short-lasting from single session therapies, but repeated rTMS sessions on consecutive days are able to produce cumulative effects. rTMS helps to release endogenous dopamine in the putamen, which has been found to affect pain processing. There are equivocal evidence on the effect of rTMS, such that one study suggests that rTMS can produce long-lasting pain relief, while another states its effects are uncertain and may be mediated by other factors such as mood. Studies have further demonstrated a frequency-dependent analgesic effect of rTMS. High frequency rTMS (5-20 Hz) demonstrate significant analgesic effects for both immediate and middle-term (e.g. weeks) therapy, whereas low frequency (0.5-1 Hz) rTMS does not. The location of the rTMS impulse application has also shown importance to treatment, with the pain-contralateral primary motor cortex (M1) being the most promising site. While mild side effects (e.g. transient headaches) of rTMS are not uncommon, severe side effects (e.g. seizures) are rare and often related to use of medications that lower the seizure threshold.
rTMS presents a promising method for managing CCNP. Research has shown that the location, frequency, and specificity of the treatment can significantly impact the technology’s effectiveness for pain management. Research on the long-term effects of rTMS for longer durations require further exploration to inform the clinical use of rTMS. Further investigation on accessibility of this technology to relevant patient populations would also be beneficial to improve our understanding on where rTMS fits in the healthcare landscape for CCNP.