Topic: Normal Pressure Hydrocephalus Subject: Medicine An 81-year-old female is brought to your office by her son. He reports a decrease in his mothers memory and prolonged delays in her responses to questions. She also has developed urinary incontinence. MRI shows dilated ventricles, but no other pathology, and a lumbar puncture reveals a normal opening pressure. Which one of the following would provide additional evidence of normal pressure hydrocephalus?