Case 23: Trapped in slow motion

An 80-year-old man is brought by his daughter due to progressive memory loss, urinary incontinence, and difficulty walking over the past 6 months. She describes his gait as “magnetic,” where he shuffles with difficulty lifting his feet. Cognitive decline has been slow, and he’s had several minor falls. CT scan shows enlarged ventricles without significant cortical atrophy. What is the most likely diagnosis, and what is the typical response to treatment?