Parkinson’s disease (PD also known as idiopathic or primary parkinsonism, hypokinetic rigid syndrome/HRS, or paralysis agitans) is a degenerative disorder of the central nervous system.
The motor symptoms of Parkinson’s disease result from the death of dopamine-generating cells in the substantia nigra, a region of the midbrain; the cause of this cell death is unknown.
Early in the course of the disease, the most obvious symptoms are movement-related; these include shaking, rigidity, slowness of movement, and difficulty with walking and gait.
Later, thinking and behavioral problems may arise, with dementia commonly occurring in the advanced stages of the disease, whereas depression is the most common psychiatric symptom.
Other symptoms include sensory, sleep, and emotional problems. Parkinson’s disease is more common in older people, with most cases occurring after the age of 50.
The main motor symptoms are collectively called parkinsonism, or “Parkinsonian syndrome”. Parkinson’s disease is often defined as Parkinson’s idiopathic syndrome (having no known cause), although some atypical cases have a genetic origin.
Many risk and protective factors have been investigated: the clearest evidence is for an increased risk of PD in people exposed to certain pesticides and a reduced risk in tobacco smokers.
The pathology of the disease is characterized by the accumulation of a protein called alpha-synuclein into inclusions called Lewy bodies in neurons and by the insufficient formation and activity of dopamine produced in certain neurons within parts of the midbrain.
Lewy bodies are the pathological hallmark of the idiopathic disorder, and their distribution throughout the Parkinsonian brain varies from one individual to another.
The anatomical distribution of the Lewy bodies is often directly related to the expression and degree of the clinical symptoms of each individual.
Diagnosis of typical cases is mainly based on symptoms, with tests such as neuroimaging being used for confirmation.
Modern treatments are effective at managing the early motor symptoms of the disease, mainly through the use of levodopa and dopamine agonists.
As the disease progresses and dopaminergic neurons continue to be lost, these drugs eventually become ineffective at treating the symptoms and at the same time produce a complication called dyskinesia, marked by involuntary writhing movements.
Diet and some forms of rehabilitation have shown some effectiveness in alleviating symptoms.
Surgery and deep brain stimulation have been used to reduce motor symptoms as a last resort in severe cases where drugs are ineffective.
Research directions include investigations into new animal models of the disease and the potential usefulness of gene therapy, stem cell transplants, and neuroprotective agents.
Medications to treat non-movement-related symptoms of PD, such as sleep disturbances and emotional problems, also exist.
Parkinson’s disease affects movement, producing motor symptoms. Non-motor symptoms, which include autonomic dysfunction, neuropsychiatric problems (mood, cognition, behavior, or thought alterations), and sensory and sleep difficulties, are also common.
Some of these non-motor symptoms are often present at the time of diagnosis and can precede motor symptoms.
A physician will diagnose Parkinson’s disease from the medical history and a neurological examination.
No lab test will identify the disease, but brain scans are sometimes used to rule out disorders that could give rise to similar symptoms.
People may be given levodopa and resulting relief of motor impairment tends to confirm diagnosis.
The finding of Lewy bodies in the midbrain on autopsy is usually considered proof that the person had Parkinson’s disease.
The progress of the illness over time may reveal it is not Parkinson’s disease, and some authorities recommend that the diagnosis be periodically reviewed.
