Parkinsons disease
Definition: Parkinson Disease is a chronic progressive neurodegenerative disorder of the basal ganglia characterized mainly by dopaminergic neuron loss in the substantia nigra pars compacta, leading to motor and non-motor symptoms.
Etiology
Primary (Idiopathic) – most common: No clear cause. Age-related degeneration
Secondary Parkinsonism: Drugs (dopamine blockers: antipsychotics, metoclopramide). Vascular parkinsonism. Toxins (MPTP). Post-encephalitic. Trauma
Pathogenesis
- Loss of dopaminergic neurons in substantia nigra
- ↓ Dopamine in striatum (caudate + putamen)
- Imbalance:
- ↓ Dopamine (inhibitory effect lost)
- ↑ Acetylcholine activity
➡️ Leads to motor symptoms (hypokinesia, rigidity, tremor)
Clinical Features
1. Motor Symptoms (Classic Triad)
A. Resting Tremor: “Pill-rolling” tremor. Worse at rest, improves with movement
B. Rigidity: “Lead-pipe” rigidity. “Cogwheel” rigidity (with tremor)
C. Bradykinesia: Slowness of movement. Difficulty initiating movement. Reduced facial expression (mask-like face)
2. Postural Instability: Falls. Stooped posture. Shuffling gait.
Gait Abnormalities: Small steps (festinating gait). Difficulty turning.Freezing episodes
Non-Motor Symptoms
Cognitive & Psychiatric: Depression. Dementia (late stage). Hallucinations
Autonomic: Constipation. Orthostatic hypotension. Urinary dysfunction. Seborrhea
Sleep Disorders: REM sleep behavior disorder
Examination Findings: Masked facies. Hypophonia (soft speech). Micrographia. Cogwheel rigidity. Rest tremor. Reduced arm swing
Diagnosis
- Clinical Diagnosis (Most Important)
- Based on: Bradykinesia + (tremor or rigidity)
- Imaging: Usually normal MRI (used to exclude other causes). DAT scan (dopamine transporter imaging) shows reduced uptake
Differential Diagnosis
1. Essential Tremor: Action tremor (not resting). No rigidity or bradykinesia
2. Drug-Induced Parkinsonism: Bilateral symptoms. History of dopamine-blocking drugs
3. Vascular Parkinsonism: Lower body predominant. Stepwise progression
4. Atypical Parkinsonism: Early falls. Poor response to levodopa
Treatment
1. Dopamine Replacement: Levodopa + Carbidopa (gold standard)
- Improves: Bradykinesia. Rigidity. Tremor (less effect)
2. Dopamine Agonists: Pramipexole. Ropinirole
3. MAO-B Inhibitors: Selegiline. Rasagiline
4. COMT Inhibitors: Entacapone
5. Anticholinergics: Useful for tremor. (e.g., trihexyphenidyl)
Advanced Treatment: Deep brain stimulation (DBS)
Complications of Treatment: Dyskinesias (from levodopa). Motor fluctuations (“on-off phenomenon”). Hallucinations