The classic symptoms of Parkinson's disease--tremors, slow movement, muscle stiffness and clumsiness--are found in other diseases. Up to 25 percent of patients diagnosed with Parkinson's disease, according to the Dana Guide to Brain Health, are found to have a different condition at autopsy. Causes of parkinsonism, other than Parkinson's disease, include degenerative neurological disorders, structural brain diseases, encephalitis, drugs and toxins. All parkinsonism-type disorders result from loss or blocking of dopamine receptors in the brain, says MayoClinic.com.
Degenerative Neurologic Disorders
Degenerative neurologic disorders that cause parkinsonism include dementia, multiple system atrophy, progressive supranuclear palsy and corticobasal degeneration. The Merck Manual says these disorders are rare, slow in onset, occur later in life and are associated with the destruction of nerve cells, particularly those using dopamine. Failure of typical Parkinson's drugs to relieve symptoms should raise suspicion of another degenerative nerve disorder.
Structural Brain Disorders
According to the Merck Manual, strokes and tumors can cause parkinsonism symptoms, depending on the part of the brain affected and nerve tissue damaged. Often symptoms affect only one side of the body, unlike Parkinson's disease. Isolated or repetitive head trauma, such as boxing or bull riding, may also result in parkinsonism.
Encephalitis
Encephalitis is an inflammation of the tissues surrounding the brain, often caused by a virus and associated with influenza-like symptoms. Encephalitis can cause parkinsonism, often with severe alterations in cognitive function. Symptoms usually resolve when the encephalitis has resolved, but low-grade parkinsonism can persist for years.
Drugs and Toxins
According to the Mayo Clinic, certain drugs can cause parkinsonism, including the neuroleptic drugs haloperidol and perphenazine. These drugs block dopamine receptors in the brain. Metoclopramide and prochlorperazine, drugs used to help the stomach empty, are chemically similar to the neuroleptic drugs and can cause parkinsonism. Certain toxins, including manganese, carbon monoxide and methanol also can block dopamine receptors, mimicking Parkinson's disease.
