Parkinsonism

Parkinsonism is a clinical syndrome defined by the presence of bradykinesia (slowness of movement) accompanied by at least one of tremor at rest, muscular rigidity, or impaired postural reflexes. It is a broader category than Parkinson’s disease and can result from a variety of causes, presenting with similar motor features but different underlying pathologies and progression.

Etiology and pathophysiology vary. The most common form is idiopathic Parkinson’s disease, associated with degeneration of dopaminergic neurons in the substantia nigra pars compacta and, in many cases, characteristic Lewy body pathology. Other causes of parkinsonism include drug-induced parkinsonism (often from dopamine receptor antagonists or antidopaminergic medications), vascular parkinsonism, metabolic or infectious conditions, toxins, and neurodegenerative syndromes such as multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration. Distinguishing among these disorders relies on the pattern of symptoms, progression, response to therapy, and sometimes imaging or specialized tests.

Clinical features commonly include bradykinesia with or without tremor, rigidity, and postural instability. Nonmotor symptoms are frequent and may include cognitive changes, mood disturbances, autonomic dysfunction, sleep disorders, and sensory symptoms. Diagnosis is clinical, supported by a good response to dopaminergic therapy in many cases and by ruling out other causes. Neuroimaging can aid in atypical cases or to exclude alternate diagnoses.

Management aims to improve motor symptoms and quality of life and is individualized. Pharmacologic treatment centers on levodopa (usually with carbidopa), supported by other dopaminergic agents such as agonists, MAO-B inhibitors, and COMT inhibitors. Nonmotor symptoms, safety, rehabilitation, and exercise are important components. In selected patients, deep brain stimulation may be considered. The prognosis varies widely and depends on the underlying cause and response to therapy; degenerative parkinsonian syndromes often have a more rapid progression and greater nonmotor burden than idiopathic Parkinson’s disease.