Psychiatryniche
A 78-year-old woman is on day six after an elective right hemicolectomy. Since the second postoperative day she has had episodes lasting about twenty minutes in which she stares, does not respond to her name and picks repeatedly at the bedclothes with her right hand, then gradually resumes conversation and has no memory of the episode. Between episodes she is orientated. She is afebrile, sodium, calcium, glucose, urea and full blood count are normal, her chart contains no opioids or sedatives, and computed tomography of the brain yesterday was normal. Which one of the following investigations should be arranged next?