## Core Concept
Progressive supranuclear palsy (PSP) is a rare brain disorder that causes serious problems with walking, balance, and eye movements, and can lead to cognitive and personality changes. It is characterized by the accumulation of tau protein in the brain, leading to neuronal degeneration. PSP is often misdiagnosed as Parkinson's disease due to overlapping symptoms.

## Why the Correct Answer is Right
The correct answer, , is associated with a statement that does not align with the typical characteristics of PSP. To determine why, let's evaluate each option in the context of PSP.

## Why Each Wrong Option is Incorrect
- **Option A:** Typically, PSP patients exhibit a distinctive feature of vertical gaze palsy, particularly downgaze, early in the disease. This symptom is a hallmark and differentiates PSP from other parkinsonian syndromes.
- **Option B:** Postural instability and falls are common early symptoms of PSP, often within the first year of symptom onset. This contrasts with Parkinson's disease, where postural instability usually occurs later in the disease course.
- **Option C:** Cognitive changes, including slowing of thought processes (bradyphrenia), difficulty with problem-solving, and changes in personality, are common in PSP. These can include apathy, disinhibition, and mood swings.
- **Option D:** Typically, PSP patients do not respond well to levodopa, a mainstay treatment for Parkinson's disease.

## Clinical Pearl / High-Yield Fact
A key clinical pearl for PSP is the early occurrence of postural instability and falls, often within the first year, which is unusual for Parkinson's disease. Additionally, the presence of downgaze palsy is highly suggestive of PSP.

## Correct Answer: D. Levodopa responsive