Parkinson's Disease – Top USMLE Diseases

Parkinson disease (PD) is a chronic, progressive neurodegenerative disorder. Although the cause is unknown, several genetic and environmental risk factors are currently being studied. Individuals present clinically with resting tremor, bradykinesia, rigidity, and postural instability. Parkinson disease is diagnosed clinically on the basis of characteristic signs and symptoms. The postmortem finding of Lewy bodies in the brain is the only confirmation for the disease. Treatment includes supportive physical and emotional care plus medications such as levodopa–carbidopa, monoamine oxidase type B inhibitors, and dopamine agonists.

Parkinson's disease (PD) is a chronic, progressive neurodegenerative disorder. Although the cause is unknown, several genetic and environmental risk factors are currently being studied. Individuals present clinically with resting tremor, bradykinesia, rigidity, and postural instability. Parkinson disease is diagnosed clinically on the basis of characteristic signs and symptoms. The postmortem finding of Lewy bodies in the brain is the only confirmation for the disease. Treatment includes supportive physical and emotional care plus medications such as levodopa/carbidopa, monoamine oxidase type B inhibitors, and dopamine agonists.

Movement disorders can be characterized as hypokinetic or hyperkinetic and often require pharmacologic management to improve the individual’s level of function. Common movement disorders include essential tremor, tics (Tourette syndrome), Parkinson disease, Huntington disease, and Wilson disease. Each of these conditions requires unique pharmacologic interventions depending on the pathophysiology and symptom severity. For example, Parkinson disease requires restoration of dopaminergic activity, while symptoms of Huntington disease are ameliorated by reducing dopamine concentrations. Although these agents can be highly beneficial, no agent is innocuous and some have potentially severe adverse events.

Medications for the management of Parkinson's disease improve the symptoms of tremor, rigidity, and postural instability by increasing dopamine levels in the brain. While levodopa is the drug of choice in individuals of any age with moderate or severe symptoms, other agents can be used as monotherapy for milder symptoms or in conjunction with levodopa–carbidopa for symptom control. Other classes of medications work by preventing central and peripheral dopamine metabolism (monoamine oxidase (MAO) type B inhibitors, catechol O-methyltransferase (COMT) inhibitors, and carbidopa), or by exerting an antidyskinetic effect (amantadine). Serious side effects include arrhythmias and psychiatric symptoms ranging from mood disorders to hallucinations and psychosis. Abrupt withdrawal can result in neuroleptic malignant syndrome–like symptoms, which can be life-threatening. Drug interactions may occur with other agents that are metabolized by the hepatic cytochrome P450 enzymes, and caution must be used to avoid serotonin syndrome.