Definition and Diagnosis
Parkinsonism refers to a clinical syndrome of tremor, rigidity, bradykinesia, and postural instability, most commonly caused by idiopathic Parkinson's disease, a progressive neurodegenerative condition resulting from loss of dopaminergic neurons in the substantia nigra.
Epidemiology
Parkinson's disease is the second most common neurodegenerative disorder after Alzheimer's disease, with prevalence increasing markedly with age and onset typically after age 60, though early-onset forms occur. It is somewhat more common in men.
Risk Factors
Risk factors include advancing age, a family history of Parkinson's disease, certain genetic mutations, exposure to specific pesticides and environmental toxins, and, protectively, factors such as caffeine intake and smoking have been associated with lower risk in observational studies.
Symptoms and Subtypes
Core motor features include resting tremor, muscle rigidity, bradykinesia (slowness of movement), and postural instability, often accompanied by a shuffling gait and reduced facial expression. Non-motor features, including depression, constipation, sleep disturbance, loss of smell, and later cognitive decline, are common and can precede motor symptoms.
Diagnosis
Diagnosis is primarily clinical, based on characteristic motor findings and response to dopaminergic medication, supported by neuroimaging to exclude other causes of parkinsonism such as vascular disease, normal-pressure hydrocephalus, or drug-induced parkinsonism.
Treatment
Levodopa combined with carbidopa remains the mainstay of treatment for motor symptoms, with dopamine agonists, MAO-B inhibitors, and other adjunctive medications used depending on disease stage. Deep brain stimulation is an option for selected patients with motor fluctuations refractory to medication, alongside physical, occupational, and speech therapy.
Prognosis
Parkinson's disease is chronic and progressive, but many individuals maintain good functional status for years with appropriate treatment. Long-term complications include motor fluctuations, dyskinesias, and, in later stages, cognitive decline and increased fall risk.
Reference
Sadock, B. J., Sadock, V. A., & Ruiz, P. Kaplan & Sadock's Synopsis of Psychiatry (11th ed.).