Question

Which of the following is/are not true about Parkinson's disease?
• [A.] Parkinson's disease is caused by the degeneration of the substantia nigra in the midbrain.
• [B.] Parkinson's disease is caused by the degenerative loss of nigrostriatal dopaminergic neurons.
• [C.] Bradykinesia, rigidity and tremor are the main symptoms in Parkinson's disease.
• [D.] Parkinson's disease is caused by the degenerative loss of nigrostriatal cholinergic neurons. Choose the correct answer from the options given below:

• A. A, B and D only
• B. A, B and C only
• C. C only
• D. D only

Hint:

Remember the classic neurochemical balance in the basal ganglia: Parkinson's disease involves a decrease in Dopamine leading to a relative increase in Acetylcholine. Therefore, it is the loss of dopaminergic neurons, not cholinergic ones, that drives the pathology.

Answer 1

The Correct Option is D

Concept: Parkinson's disease is a progressive neurodegenerative disorder primarily affecting the motor system. It is characterized pathologically by the selective loss of dopaminergic neurons within the pars compacta region of the substantia nigra, situated in the midbrain. This loss results in a significant reduction of dopamine delivery to the striatum, disrupting voluntary motor control pathways.

Step 1: Evaluation of Statement A Statement A asserts that Parkinson's disease is caused by the degeneration of the substantia nigra in the midbrain. This is a well-established pathophysiological fact. The progressive destruction of melanin-containing neurons in this region is the hallmark of the disease. Therefore, Statement A is true.

Step 2: Evaluation of Statement B Statement B states that the condition is caused by the degenerative loss of nigrostriatal dopaminergic neurons. Dopamine is the primary neurotransmitter involved in the communication between the substantia nigra and the striatum (the nigrostriatal pathway). The depletion of these dopaminergic neurons leads to classic motor dysfunction. Therefore, Statement B is true.

Step 3: Evaluation of Statement C Statement C lists bradykinesia (slowness of movement), rigidity (stiffness of limbs), and resting tremors as the main clinical symptoms. These, along with postural instability, constitute the classic motor tetrad used for diagnosing Parkinson's disease. Therefore, Statement C is true.

Step 4: Evaluation of Statement D Statement D claims that Parkinson's disease is caused by the degenerative loss of nigrostriatal cholinergic (acetylcholine-releasing) neurons. In Parkinson's disease, the primary defect is a deficiency of dopamine, which causes a relative *overactivity* of cholinergic neurons in the striatum, rather than their degenerative loss. Central anticholinergic drugs are actually used in treatment to restore the balance. Therefore, Statement D is false. Since the question asks for the statement(s) that are NOT true, only statement D fulfills this criterion.