Myoclonus is a sudden and brief muscle twitch that you can't control. There are two types of myoclonus:
- Physiologic myoclonus, which is normal and happens to most people, involves quick muscle twitches. Hiccups and a jerking motion when you're falling asleep are examples of this kind of myoclonus.
- Pathologic myoclonus causes more widespread and long-lasting muscle twitches. These are a sign of a brain or nerve condition. Pathologic myoclonus can also be a sign of a reaction to a medication.