MRCP2-3106

A 16-year-old girl presents after collapsing in a supermarket. She experienced hot and sweaty sensations, along with blurred vision before losing consciousness. Her mother reports that she was unresponsive and had limb twitching for twenty seconds before regaining consciousness. The patient has had three similar episodes in the past and her older brother has epilepsy. Although her ECG showed normal sinus rhythm, she felt nauseous and had urinary incontinence. What test is most likely to provide an accurate diagnosis?