Ketamine and fMRI for Neuropathic Pain

Overview

Neuropathic or nerve injury related pain (NP), an extremely unpleasant condition that is difficult to treat, often has a severe, persistent, and unremitting course. Conventional treatments are often ineffective in relieving NP. Recently, the investigators have developed a cost-efficient regimen involving use of low dose infusions of ketamine for treating neuropathic pain in patients in whom oral medications have failed. We have observed excellent benefits in many of these patients. However, this treatment requires titration and monitoring during the infusion and currently it is not possible to predict which patients will benefit from this intervention. The investigators have shown that functional magnetic resonance imaging (fMRI) of the brain can be used as a tool to predict relief of pain and to assess the effect of treatment in some chronic pain conditions. This innovative project involves development of an fMRI-guided treatment with intravenous ketamine in patients with NP. This study aims to analyze patterns of changes in fMRI of the brain, before and after infusion of ketamine and to correlate the changes with pain intensity. The information from this study will help to deliver this therapy earlier to those patients who are most likely to benefit from ketamine.

This trial is exploratory, prospective, non-randomized, single cohort, single-center, with no blinding of participants, treating physicians, and investigators. Study participants undergo a resting-state fMRI before, after and at '1-month post-ketamine infusion' (standard care). Patients will be recruited over 2 years, from Pain Clinics at Toronto Western Hospital and Mount Sinai Hospital. The primary null hypothesis for this trial is that there are no fMRI brain patterns of patients with neuropathic pain that predict pain relief following ketamine infusion. The secondary null hypothesis for this trial is that there are no correlations between specific fMRI brain patterns of patients with neuropathic pain and change in intensity of pain immediately following ketamine infusion. Further secondary hypothesis include that cortical reorganization in the brain as measured by fMRI at one month after the infusion of ketamine does not correlate with persisting analgesic benefit in patients with neuropathic pain. Finally, we hypothesize that ketamine infusions do not provide significant pain relief, reduction in anxiety and depression, and improvement in quality of life early (at 1 month) and late (at 3 months) after the infusions in patients with neuropathic pain.