Analgesic Effects of Directed Repetitive Transcranial Magnetic Stimulation in Acute Neuropathic Pain After Spinal Cord Injury

Abstract

Objectives: Central neuropathic pain (CNP) often appears following spinal cord injury (SCI), but current treatments are not always successful. In this study, we evaluated the analgesic effects of repetitive transcranial magnetic stimulation (rTMS) applied over the hand area of the motor cortex in patients with acute CNP after SCI.

Methods: A total of 48 patients with complete or incomplete SCI and acute CNP participated in this study and were randomized to receive either rTMS (10 Hz, 1,500 stimuli; N = 24) or a sham intervention (N = 24) for three weeks. The numeric rating scale (NRS) and Short-Form McGill Pain Questionnaire-2 (Chinese Edition; SF-MPQ-2-CN) were analyzed to assess the degree of pain. Brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) were collected to explore expression influenced by rTMS. Motor-evoked potential (MEP) latency and maximal amplitude were measured to determine neurophysiological changes. The assessments were carried out at baseline (T0), three days (T1), one week (T2), two weeks (T3), and three weeks (T4) after onset of treatment.

Results: The analysis showed significant treatment-time interactions for the quality and intensity of pain, as measured by NRS (P < 0.001, η2 = 0.441) and SF-MPQ-2 (P < 0.001, η2 = 0.590). Compared with the sham group, the NRS and SF-MPQ2-CN scores were significantly lower on the third day (P < 0.001, Cohen's d = 1.135; P = 0.006, Cohen's d = 0.616) and after one week (P < 0.001, Cohen's d = 0.846; P = 0.012, Cohen's d = 0.557) of treatment. In addition, the serum levels of BDNF and NGF were significantly higher in the treated group after three weeks (P = 0.015, Cohen's d = 0.539; P = 0.009, Cohen's d = 0.580), and the MEP amplitude increased by 109.59% (P = 0.033, Cohen's d = 0.464).

Conclusions: These findings indicate that 10 Hz rTMS over the hand area of the motor cortex could alleviate acute CNP in the early phase of SCI and could enhance MEP parameters and modulate BDNF and NGF secretion.

Keywords: Brain-Derived Neurotrophic Factor; Central Neuropathic Pain; Motor-Evoked Potential; Nerve Growth Factor; Repetitive Transcranial Magnetic Stimulation; Spinal Cord Injury.