Secondary parkinsonism is similar to Parkinson's disease, but it is caused by certain medicines, a different nervous system disorder, or another illness.

Parkinson's disease is one of the most common nervous system (neurologic) disorders of the elderly. "Parkinsonism" refers to any condition that causes Parkinson's-type abnormal movements. These movements are caused by changes in or destruction of the nerve cells (neurons) that produce the chemical dopamine in a certain area of the brain.

Secondary parkinsonism may be caused by disorders such as:

• Encephalitis
• Meningitis
• Stroke

Other disorders can also damage the dopamine neurons and produce this condition, including:

• Corticobasal degeneration
• Diffuse Lewy body disease
• Multiple system atrophy
• Progressive supranuclear palsy

Another common cause of secondary parkinsonism is medication, such as:

• Antipsychotics (haloperidol)
• Metoclopramide
• Phenothiazine medications

If they damage the area of the brain that contains the dopamine neurons, the following may cause secondary parkinsonism:

• Brain damage caused by anesthesia drugs (such as during surgery)
• Carbon monoxide poisoning
• Exposure to toxins
• Overdoses of narcotics

There have been cases of secondary parkinsonism among intravenous drug users who injected a substance called MPTP, which can be produced when making a form of heroin. These cases are rare and have mostly affected long-term drug users.

Secondary parkinsonism caused by antipsychotics or other medications is usually reversible if identified soon enough. However, it may not be reversible if it is caused by:

• Drug-related brain damage
• Infections
• Toxins