Myoclonus

Vignette:

A 40 year old woman with metastatic breast cancer has had myoclonus for the last 24 hours as exhibited by involuntary muscle twitches bilaterally. Her pain is palliated on Fentanyl patch which was decreased from 150 mcg to 100 mcg. She has received one dose of hydromorphone 2 mg IV in the past 24 hours for breakthrough pain. Her kidney function is unknown. Patient denies discomfort from the twitching and her pain is palliated. Should anything be done about the myoclonus?

Discussion:

Myoclonus may develop in response to infection, spinal cord injury, brain tumors, stroke, kidney or liver failure, or as a side effect of certain drugs (such as opioids, and quinolones). Evaluate all potential causes for this patient as well as observation to ensure myoclonus is not due to seizure activity. If Fentanyl is the suspected cause, consider rotating to another opioid. Monitor urine output. If symptoms are uncomfortable, consider benzodiazepines for relief of muscle twitches especially at night to encourage sleep.

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