While Parkinson's disease is primarily a disorder of movement, it may also have significant effects on mood and memory. Depression is commonly seen in the early stages of the disease. An anxiety disorder may also occur. Patients in later stages of the disease may have difficulties with memory. Some patients may also show hallucinations or psychosis in response to medications.
It is estimated that about half of people with Parkinson's may suffer from depression. This is not merely a reaction to the diagnosis but an intrinsic part of the disease process. In addition to dopamine, deficits in the brain that are responsible for the motor symptoms, there are also alterations in levels of other neurotransmitters that can affect mood. In particular, deficits of serotonin may be associated with depression. In about 20% of people with Parkinson's disease, depression may precede motor symptoms.
Treatment involves use of serotonin reuptake inhibitors (SSRIs) such as fluoxetine (Prozac), paroxetine (Paxil), and sertraline (Zoloft). Caution must be excercised when using these agents in combination with selegeline (Eldepryl).
About 40% of people with Parkinson's disease suffer from anxiety. At times it may be severe enough to take the form of panic attacks. Symptoms may include breathlessness, sweating, chest discomfort, choking, and dizziness. In severe cases patients may have feelings such as fear of dying, or of going insane. Patients with on-off fluctuations have more anxiety in the off phase. The relationship of anxiety to medications for PD is unclear. Treatment involves using SSRIs just as for depression.(See above) Benzodiazapenes such as Ativan, Xanax or Klonopin are also helpful.
Levodopa and all dopamine agonists can have significant adverse effects including hallucinations and psychosis. The incidence of these is greater with more advanced disease and with higher doses of medications. At their mildest these can take the form of vivid dreams. The next stage is mild visual hallucinations with the patient being aware of the fact that he or she is hallucinating. Visual hallucinations are the most common and take the form of well-formed, nonthreatening images of persons or animals. More significant adverse effects can involve frank psychosis or delusional thinking. The patient may be suspicious, agitated or confused. In severe cases hospitalization may be required.
Dopamine agonists and agents with anticholinergic effects such as Artane and Symmetrel are more likely to cause hallucinations than Sinemet. The slow release form of Sinemet CR is more likely to cause hallucinations than regular Sinemet.
Treatment involves lowering or stopping adjunctive agents and trying to work with Sinemet alone as far as possible. The newer antipsychotic agents such as Seroquel are also very helpful in controlling severe hallucinations.
Dementia in Parkinson's Disease
About 15 to 25% of individuals with PD will suffer from memory and cognitive deficits significant enough to be called dementia. As expected, the incidence is greater in older patients. Cognitive disturbances may range from mild deficits to global dementia. Mild cognitive deficits are common in PD and are characterized by lack of flexibility in thought, psychomotor slowing, difficulty learning new information, and impaired visual-spatial skills. Mild deficits in short-term memory are also common and may progress to more severe memory deficits. Language skills are relatively spared although some studies have found a mild impairment in naming. Higher executive function, a term that involves abstract thinking, planning abilities, judgment, and initiative, is often affected in patients with IPD.
Not much is available for treatment of dementia in the setting of PD although drugs such as Aricept and Exelon which are primarily used in the treatment of Alzheimer's disease are sometimes tried.