A 62-year-old man from Delhi presents with a 3-year history of progressive tremor at rest, rigidity, and bradykinesia. Examination reveals a resting tremor that disappears with intentional movement, cogwheel rigidity in the upper limbs, and difficulty initiating gait. MRI brain is normal. Based on the clinical presentation consistent with Parkinson disease and the anatomical dysfunction of the basal ganglia circuits, what is the most appropriate next step in management?

Explanation

## Clinical Context The patient presents with the cardinal triad of Parkinson disease: resting tremor, rigidity, and bradykinesia. The normal MRI rules out secondary causes (structural lesions, atrophy patterns). The clinical diagnosis is established. ## Pathophysiology of Basal Ganglia Dysfunction **Key Point:** In Parkinson disease, degeneration of dopaminergic neurons in the substantia nigra pars compacta leads to loss of dopamine in the striatum. This disrupts the balance between the direct (facilitation) and indirect (inhibition) motor pathways through the basal ganglia. ```mermaid flowchart TD A[Dopamine loss in striatum]:::outcome --> B{Pathway imbalance}:::decision B -->|Direct pathway inhibited| C[Reduced thalamic excitation]:::outcome B -->|Indirect pathway overactive| D[Excessive thalamic inhibition]:::outcome C --> E[Bradykinesia & rigidity]:::outcome D --> E E --> F[Levodopa restores dopamine]:::action ``` ## Management Algorithm **High-Yield:** Levodopa-carbidopa is the gold standard pharmacotherapy for symptomatic Parkinson disease. Carbidopa is a peripheral decarboxylase inhibitor that prevents premature conversion of levodopa to dopamine before it crosses the blood-brain barrier. | Intervention | Indication | Timing | |---|---|---| | Levodopa-carbidopa | Symptomatic PD with functional impairment | First-line, start early | | Functional MRI | Research tool, not diagnostic | Not standard of care | | Genetic testing | Family history or early-onset PD (<40 yrs) | Optional, not first-line | | DBS surgery | Motor complications, failed medical management | Second-line, after 4–5 yrs therapy | **Clinical Pearl:** The patient is 62 years old with a 3-year disease duration—ideal for initiating dopaminergic therapy. DBS is reserved for patients with motor fluctuations or dyskinesias refractory to medication, not as first-line treatment. **Tip:** In NEET PG, when a patient with confirmed Parkinson disease has functional impairment and no contraindications, always choose pharmacotherapy initiation over imaging or surgery.