A 35 year old widow presents with several episodes of jerky movements during the past 1 week. The movements began in her left shoulder and subsequently spread down to her left arm and both legs.

Each episode lasted for 1 to 2 minutes, and was followed by 10 to 15 seconds of gagging and apnea. She was fully awake and aware at all times. She also complains of difficulty in walking after these episodes started.

Her medical and family histories are unremarkable, and she is not on any medications. Her daughter died 4 years ago, at the age of 3; she required several sessions of counselling at that time.