A 70-year-old male patient is diagnosed with Parkinson's disease

A 70-year-old male patient is diagnosed with Parkinson's disease

A 70-year-old male patient is diagnosed with Parkinson's disease. Which of the following is the primary pathological finding in this disease?

A. Loss of dopaminergic neurons in the substantia nigra pars compacta

B. Amyloid plaques in the cerebral cortex

C. Neurofibrillary tangles in hippocampal neurons

D. Loss of motor neurons in the anterior horn of the spinal cord

Answer: A

Explanation: Parkinson's disease is characterized by progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta, leading to reduced dopamine levels in the striatum (caudate nucleus and putamen). This causes the classic symptoms: tremor, rigidity, bradykinesia, and postural instability. Amyloid plaques and neurofibrillary tangles are pathological findings of Alzheimer's disease (B, C are incorrect). Loss of motor neurons is seen in amyotrophic lateral sclerosis (ALS, D is incorrect).