**Question:** In Alzheimer's disease, the characteristic lesion is seen in

A. Amyloid plaques
B. Neurofibrillary tangles
C. Vascular lesions
D. Glial cells

**Core Concept:** Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline and memory impairment. The pathological hallmarks of AD are amyloid plaques and neurofibrillary tangles, which are present in the brain.

**Why the Correct Answer is Right:** The correct answer is B (Neurofibrillary tangles). Neurofibrillary tangles are intracellular aggregates of hyperphosphorylated tau protein, which leads to the disruption of microtubules, impairing neuronal transport and causing cell dysfunction. This is the primary pathological feature of Alzheimer's disease and contributes to neuronal death and dementia.

**Why Each Wrong Option is Incorrect:**

A. Amyloid plaques (A) are extracellular aggregates of amyloid-beta peptides, which do not solely cause the disease but are associated with neuronal loss and inflammation.

B. Vascular lesions (C) are unrelated to Alzheimer's disease and are more commonly seen in cerebrovascular disease or small vessel disease.

D. Glial cells (D) are involved in the inflammatory response and neuroprotection but are not the primary cause of Alzheimer's disease.

**Clinical Pearl:** Alzheimer's disease is the most common cause of dementia in older adults, affecting millions globally. Understanding the pathological features, such as neurofibrillary tangles and amyloid plaques, is essential for appropriate diagnosis and patient management.