Treatment of Neuropathic Pain Following Spinal Cord Injury - a rTMS Approach

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Approximately 86,000 Canadians live with a spinal cord injury (SCI). Individuals with a SCI experience varying levels of deficits in motor and sensory function and sometimes paralysis. SCI can result in permanent impairments both physical and psychological, as the loss of body function greatly impacts quality of life. Neuropathic pain (NP) is a common complication following SCI. Damage or dysfunction to the nervous system after SCI commonly leads to secondary injury or disease in the somatosensory system, which may contribute to NP. This debilitating complication can impede many factors including physical function, rehabilitation, sleep, and return to work. Treatment modalities for NP aim to reduce pain and improve function and quality of life. Pharmacological interventions are considered first-line therapy for NP management, though there remains limited evidence to support the efficacy of this treatment modality. Pharmacologic therapies may also include negative side effects. Additionally, clinical guidelines for NP management recommend including non-pharmacologic strategies. Therefore, an interdisciplinary strategy may be required to effectively mitigate NP after SCI. Evidence of neuromodulation techniques to improve various pain conditions is well established, and reductions in pain may be related to the modified brain activity. Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive neuromodulation intervention with a low risk of adverse effects. Preliminary studies investigating rTMS for NP after SCI have shown a therapeutic effect after treatment whereby quality of life and pain improved in this population. RESEARCH QUESTION AND OBJECTIVES This study aims to determine the clinical feasibility of a rTMS protocol to improve pain symptomology in adults with NP following SCI. Additionally, this study will contribute to the limited body of evidence for the efficacy of this treatment modality in this population. The primary objective is to determine symptomatic changes in pain profile and treatment response using the International Spinal Cord Injury Pain Basic Data Set (ISCIPBDS) v3.0, a standardized tool from the American Spinal Injury Association (ASIA), and the PROMIS Scale Neuropathic Pain Quality 5a questionnaire. Secondary objectives include assessing quality of life (QLI-SCI), depression (PHQ-9), anxiety (GAD-7), disability (WHODAS), and pain catastrophizing (PCS). METHODS Clinical Assessments: Demographic information, including age, sex, and past medical history will be collected prior to participation. Participant's neurological level of impairment will be determined by a treating physician, allied health professional, or research study physician. The initial assessment will include answering questionnaires: the International Spinal Cord Injury Pain Basic Data Set (ISCIPBDS) v3., PROMIS Scale Neuropathic Pain Quality 5a questionnaire, Quality of Life Index Spinal Cord Injury v3 (QLI-SCI), Pain Catastrophizing Scale (PCS), World Health Organization Disability Assessment Schedule (WHODAS) 2.0, Generalized Anxiety Disorder scale-7 (GAD-7), and the Patient Health Questionnaire-9 (PHQ-9). Participant's medication usage will be monitored during the study and rTMS tolerability will be assessed immediately following each treatment session. Participants will be asked to complete the above-mentioned questionnaires post-rTMS treatment, at 1 and 3 months after their last rTMS treatment. TMS Protocol: Participants will undergo high frequency rTMS sessions 5 days a week for 4 weeks (20 treatments total). Daily rTMS sessions will include 10 trains of 60 pulses (600 pulses total) at a frequency of 10 Hz, with an inter-train interval of 45-seconds. Treatment intensity will be applied at 100-120% of the participant's resting motor threshold (RMT). A RMT is the minimal intensity required to evoke a motor evoked potential and will be obtained by administering single-pulse TMS to the left motor cortex. Electromyography (EMG) electrodes will be placed on the contralateral abductor pollicis brevis (APB) muscle to determine the motor evoked potential peak-to-peak amplitude, requiring 50 microvolts amplitude in 5 of 10 consecutive stimulations. The rTMS treatment will be administered to the dorsolateral prefrontal cortex (DLPFC) which will be located using Montreal Neurologic Institute (MNI) coordinates (-50, 30, 36). Participants will be seated in a comfortable chair or their wheelchair for each rTMS session.