Parkinson's disease causes a significant decrease in dopamine in the brain, resulting in problems with motor function. The dopamine decrease occurs because there's an abnormal destruction of specific neurons that produce the neurotransmitter. Parkinson's disease patients can also have hallucinations, in which they perceive something that does exist. Different factors can contribute to the onset of these hallucinations.
Depression
Patients with Parkinson's disease may develop depression. Patients may have persistent sadness or irritability, and can experience inappropriate guilt. Depression may contribute to the hallucinations that Parkinson's disease patients have.
A study published in 2000 in the journal "Brain" explains that depression can trigger hallucinations in people who have sensory deficits such as hearing problems. Parkinson's disease patients with depression can have presence hallucinations, in which they sense the presence of someone such as a decreased loved one. In the study, 8 percent of patients had a presence hallucination.
Medications
The Parkinson's Disease Society points out that patients taking anticholinergics or dopamine agonists, two medications used to treat Parkinson's disease, have a higher risk of hallucinations. These two medications affect the level of dopamine, which may contribute to the hallucinations. Other Parkinson's disease medications can contribute to hallucinations. For example, MayoClinic.com notes that catechol O-methyltransferase inhibitors, a medication that prolongs the effects of the medication combination carbidopa and levadopa, can worsen the hallucinations caused by levadopa. If patients take glutamate-blocking drugs in the later stages of Parkinson's disease, the drugs can cause hallucinations. Another medication for the disease, MAO-B inhibitors, rarely cause hallucinations.
Progression of Parkinson's Disease
As Parkinson's disease progresses into the more advanced stages, the changes made by the disease can cause the hallucinations. For example, the "Brain" study notes that cognitive impairments from Parkinson's dementia, a deterioration of neurological functioning, can cause visual hallucinations. The authors also found that patients with more severe motor problems had hallucinations.
Vision Problems
Problems with vision can contribute to hallucinations in Parkinson's disease patients. The Parkinson's Disease Society points out that severely impaired vision may cause visual hallucinations in some patients.
Sleep Disorders
Parkinson's disease patients who have daytime sleepiness may have visual hallucinations, the "Brain" study demonstrated. The hallucinations that these patients have occur during the evening or night. Lesions on the brain stem, the part of the brain related to sleep, may contribute to these hallucinations.
