30. Which of the following diseases is characterized by predominant motor dysfunction that results
from the progressive degeneration of the nigrostriatal dopamine pathway?
1. Parkinson’s Disease
2. Alzheimer’s Disease
3. Schizophrenia
4. Huntington’s Disease

Parkinson’s Disease: A Neurodegenerative Disorder Affecting Motor Functions

Introduction

Parkinson’s Disease (PD) is a progressive neurodegenerative disorder primarily affecting motor functions due to the loss of dopamine-producing neurons in the nigrostriatal pathway. This condition leads to characteristic symptoms such as tremors, bradykinesia (slowness of movement), muscle rigidity, and postural instability.

Among the given options, the correct answer is:

✅ 1. Parkinson’s Disease

Keyphrase: Parkinson’s Disease and Nigrostriatal Dopamine Degeneration

Understanding Parkinson’s Disease (PD)

What Causes Parkinson’s Disease?

The main cause of Parkinson’s Disease is the progressive degeneration of dopaminergic neurons in the substantia nigra of the brain. This results in a decrease in dopamine levels, which disrupts normal motor control.

Key Features of PD:

1. Loss of Dopaminergic Neurons:

   • The nigrostriatal pathway, which connects the substantia nigra to the striatum, is responsible for dopamine transmission.

   • Dopamine is essential for coordinating smooth and controlled movements.

   • As the neurons die, motor control is impaired.

2. Presence of Lewy Bodies:

   • Abnormal aggregates of the protein alpha-synuclein called Lewy bodies accumulate in neurons, contributing to neuronal death.

Symptoms of Parkinson’s Disease

Motor Symptoms:

• Tremors: Involuntary shaking of hands, legs, or jaw.

• Bradykinesia: Slowed movement, difficulty in initiating movements.

• Muscle Rigidity: Stiffness in limbs and resistance to movement.

• Postural Instability: Impaired balance, leading to frequent falls.

Non-Motor Symptoms:

• Cognitive impairment (later stages)

• Sleep disturbances

• Depression and anxiety

• Loss of sense of smell (anosmia)

Why Are Other Options Incorrect?

1. Alzheimer’s Disease (AD):

   • Primarily affects memory and cognitive functions.

   • Associated with beta-amyloid plaques and neurofibrillary tangles.

2. Schizophrenia:

   • A psychiatric disorder causing hallucinations, delusions, and disorganized thoughts.

   • Linked to dopamine imbalance, but not due to nigrostriatal degeneration.

3. Huntington’s Disease:

   • A genetic neurodegenerative disorder affecting motor control and cognition.

   • Caused by CAG repeat expansions in the HTT gene, leading to abnormal involuntary movements (chorea).

Diagnosis of Parkinson’s Disease

There is no definitive test for Parkinson’s, but diagnosis is based on:

• Neurological examination

• Response to dopamine-based medications

• Brain imaging (MRI, DaTscan) to rule out other conditions

Treatment and Management

1. Medications:

   • Levodopa (L-DOPA): Converts into dopamine in the brain.

   • Dopamine Agonists: Mimic dopamine effects (e.g., Pramipexole, Ropinirole).

   • MAO-B Inhibitors: Slow dopamine breakdown (e.g., Selegiline, Rasagiline).

2. Surgical Treatments:

   • Deep Brain Stimulation (DBS): Electrodes implanted in the brain to regulate movement.

3. Lifestyle and Supportive Therapies:

   • Physical therapy to improve mobility.

   • Speech therapy for communication difficulties.

Conclusion

Parkinson’s Disease is a progressive movement disorder caused by nigrostriatal dopamine pathway degeneration. Among the given options, Parkinson’s is the correct answer, as it directly correlates with dopaminergic neuron loss.

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