Parkinson's Disease: Symptoms, Causes, and Treatment Overview

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by loss of dopaminergic neurons in the substantia nigra pars compacta, leading to motor and non-motor symptoms.

Cardinal Motor Symptoms (TRAP)

• Tremor: Resting, pill-rolling, typically asymmetric onset.
• Rigidity: Cogwheel or lead-pipe; reduces range of motion.
• Akinesia/Bradykinesia: Slowness, reduced amplitude, difficulty initiating movement.
• Postural instability: Later feature; retropulsion, falls.

Non-Motor Symptoms (Often Precede Motor)

• Anosmia, REM sleep behavior disorder, constipation, depression, anxiety.
• Cognitive impairment, dementia (later stages).
• Autonomic dysfunction: orthostatic hypotension, urinary urgency, sexual dysfunction.
• Pain, fatigue, speech/swallowing difficulties.

Risk Factors

• Age (>60), male sex, family history (15% have affected relative).
• Genetic: SNCA, LRRK2, GBA mutations (rare familial forms).
• Environmental: Pesticide/herbicide exposure (paraquat, rotenone), well water, rural living; head trauma. Smoking and caffeine associated with lower risk.

Treatment

Pharmacologic

• Levodopa/carbidopa: Gold standard; replaces dopamine.
• Dopamine agonists: Pramipexole, ropinirole, rotigotine (patch).
• MAO-B inhibitors: Rasagiline, selegiline (mild symptomatic benefit, possible neuroprotection).
• COMT inhibitors: Entacapone, opicapone (prolong levodopa).
• Amantadine: For dyskinesia.
• Anticholinergics: Benztropine, trihexyphenidyl (tremor; avoid in elderly).

Surgical

• Deep Brain Stimulation (DBS) of STN or GPi: For motor fluctuations/dyskinesia refractory to meds.
• Focused ultrasound thalamotomy: Tremor-dominant, non-invasive option.

Rehabilitative

• Physical therapy (LSVT BIG), occupational therapy, speech therapy (LSVT LOUD), exercise (aerobic, resistance, balance).

Prognosis

Variable progression. With modern multidisciplinary care, many maintain independence for 10–20+ years. Research focuses on disease modification (alpha-synuclein targeting, gene therapy, neuroprotection).