The neurocognitive effects of 5 day anesthetic ketamine for the treatment of refractory complex regional pain syndrome

Background Complex regional pain syndrome I (CRPS) is characterized by severe neuropathic pain that exceeds the severity of an injury and is refractory to traditional treatments. Recent experimental interventions include ketamine infusion therapy. Objective We sought to evaluate the physical, neurocognitive, and emotional effects of extended treatment with anesthetic doses of ketamine in refractory CRPS I patients. Methods Nine patients (eight females) received a neuropsychological evaluation pre- and 6 weeks post-treatment that evaluated intellectual and academic abilities, executive functioning/processing speed, attention, learning and memory, and motor functioning. Mood/affect and personality were also evaluated and patients completed an extensive pain questionnaire. Results There was a marked reduction in the report of both acute and overall pain after treatment. Brief attention and processing speed improved significantly post-treatment, whereas all other cognitive domains remained stable, with the exception of a mild decline in motor strength. Conclusions Findings suggest that, at least at a 6-week follow up: (1) deep ketamine therapy is effective for relief of pain CRPS I and (2) there were no adverse cognitive effects of extended treatment with deep ketamine infusion. No definitive conclusions could be drawn about the relationship between mood and personality factors and the presence of CRPS I.