Myoclonus is a relatively rare involuntary movement that is often observed in palliative care settings and that can cause patient distress. The purpose of this study is to investigate the occurrence of myoclonus and countermeasures against it in terminally ill patients with cancer diagnosed by palliative care specialists at Komaki City Hospital, Japan. We retrospectively reviewed patients with terminal cancer who received palliative care consultations between January 2018 and May 2019 and who were diagnosed with myoclonus by palliative care specialists, using electronic medical records. Patient demographics, time from onset of myoclonus to death, daily opioid use, countermeasures, and outcome of myoclonus were assessed. Of 360 patients examined during this period, 45 (12.5%) were diagnosed with myoclonus. Median age was 71 (range, 43-88) years; median time from onset of myoclonus to death was 8 days (range, 0-56); opioid usage was present in 39 patients (morphine, oxycodone, and fentanyl: n = 6, 21, and 12, respectively); and median oral morphine equivalent at onset of myoclonus was 60 mg (range, 12-336 mg). Myoclonus treatment was administered to 21 patients (opioid dose reduction, opioid switching, and others: n = 14, 3, and 4, respectively). Myoclonus is a common complication in patients with terminal cancer.
Keywords: Cancer; myoclonus; opioid; palliative care; terminal illness; treatment.