A 43-year-old woman presented to her general practitioner with increasing daytime tiredness. She had a history of nocturnal events from early childhood and these were occasionally associated with falls and injuries. Although she had no memory of these, she was told that she would wake up and walk around clumsily, sometimes engaging in or initiating limited conversation and performing simple tasks such as switching on the television or opening the front door. On one occasion she was found in the street outside her house in her nightdress; her partner subsequently hid the house key from her each evening.

The episodes lasted approximately 30 min and occurred only once per night, normally within an hour or so of going to bed. They occurred three to seven times a week, exclusively at night and in her own home—never elsewhere. If she drank excessive alcohol during the evening before, the events did not occur. Her neurological and cardiovascular examination was normal, as was her electrocardiogram.