**Core Concept**
Alien limb syndrome is a rare neurological disorder characterized by involuntary movements of a limb, often without the patient's control or awareness. It results from damage or dysfunction in specific brain regions, particularly those involved in motor control and cognition.

**Why the Correct Answer is Right**
Alien limb syndrome is most commonly associated with corticobasal degeneration (CBD), a progressive neurodegenerative disorder that affects motor control, cognition, and behavior. CBD is characterized by the accumulation of tau protein in the brain, leading to the degeneration of neurons in the cerebral cortex and basal ganglia. The damage to these regions disrupts normal motor function, resulting in the characteristic symptoms of alien limb syndrome. In CBD, the affected limb often exhibits involuntary movements, such as flinging, grasping, or posturing, which can be difficult to control or suppress.

**Why Each Wrong Option is Incorrect**
**Option B:** Diffuse Lewy body disease is a neurodegenerative disorder characterized by the presence of Lewy bodies in the brain, which can lead to cognitive decline and motor symptoms, including parkinsonism. However, alien limb syndrome is not a characteristic feature of this disease.

**Option C:** Fronto-temporal dementia is a group of neurodegenerative disorders primarily affecting the frontal and temporal lobes of the brain. While fronto-temporal dementia can cause changes in behavior and motor function, alien limb syndrome is not a typical symptom.

**Option D:** Alzheimer's disease is a progressive neurodegenerative disorder primarily affecting memory, cognitive function, and behavior. Alien limb syndrome is not a characteristic feature of Alzheimer's disease.

**Clinical Pearl / High-Yield Fact**
It is essential to differentiate corticobasal degeneration from other neurodegenerative disorders, as CBD often presents with a unique combination of motor and cognitive symptoms, including alien limb syndrome, myoclonus, and prominent apraxia.

**✓ Correct Answer: A. Corticobasal degeneration**