Does ALS progress in episodes?

ALS usually progresses slowly. In rare cases, the onset of the disease can occur over the course of a few hours or days, so that the early stage appears as a “flare-up” or acute symptoms. It is also possible for patients to suddenly lose the ability to perform certain functions from one day to the next. This functional deficit can also be experienced as a “flare-up,” even though the underlying process of neurodegeneration is largely continuous. This phenomenon can be understood in terms of the proverbial last drop that causes the glass (of the disease) to overflow.