Recognizing and Treating Neuropsychiatric Symptoms in Parkinson's Disease

A post-hoc analysis of the ADAGIO study (rasagiline or placebo in PD patients taking antidepressants) found that rasagiline use was associated with a nonsignificant slowing of apathy development during the trial [54].

Psychosis

Psychotic symptoms are a common occurrence in drug-treated patients, with visual hallucinations occurring in up to 30%, though over a 20-year period up to three-quarters of patients may develop visual hallucinations.After visual, the most common type of hallucination is auditory, followed by the other affected senses such as tactile, olfactory, or even taste [57]. Delusions, which tend to be paranoid in nature, occur in about 5% of patients [55–57]. The presence of psychotic symptoms is associated with poorer quality of life [58].

Symptomatology

The visual hallucinations of PD are usually quite stereotyped, and have been described as “minor” and “non-minor”[59]. Minor hallucinations refer to transient peripheral field stimuli that disappear when brought into central focus, “something flashed by,” a sense of a living being nearby, “a presence in the room,” or illusions whereby objects are transformed, eg, a bush in the yard is a deer.

Auditory hallucinations tend to be vague or indistinct sounds, like music in another room as opposed to voices speaking directly to the patient as might be experienced in a primary psychotic disorder. Tactile forms often involve insects or other animals crawling on the skin. Olfactory hallucinations may take the form of smelling perfume, toxic odors from room vents, etc.

Early in the experience, the visual hallucinations may be amusing in that they consistently remain nonthreatening, similar day to day, and sometimes oddly provide an aspect of comfort or companionship to the patient. More commonly, the hallucinations are bothersome to the patient because the experience indicates to the patient that there is something wrong with their mind. Visual hallucinations often begin in low-stimulus environments, often in the evening or other low-light conditions, but as the problem advances they can occur at any time of day. While visual hallucinations may initially occur for only seconds at a time many days apart, the frequency and duration can increase until they occur hours at a time every day and are accompanied by multiple other visual hallucinations, delusions, and confusion [60].

Delusions tend to be more distressing to patients and caregivers because they are often paranoid in nature. The patient is more likely to act out due to the anxiety the paranoia creates. For example, she may change passwords to online accounts due to a belief that unknown assailants are after her finances. He may go to great lengths trying to prove his wife is cheating.

Risk Factors

While the primary risk factor for psychotic symptom development is dementia [57], it occurs in nondemented patients. Other associations include reduced visual acuity [56], visual processing impairment [61–65], use of dopamine agonists, REM behavior disorder, duration of PD, axial rigidity subtype of disease [61,66–68]. The pathophysiology of psychosis in PD is likely complex and remains currently unexplained. The role of excess dopamine has been described above, but there is also data suggesting cholinergic deficits in the cortex may also contribute. Excess serotonin (increased 5HT2A receptor subtypes) in the temporal lobe within the visual processing pathway has been postulated to be of significance [69,70]. Hypometabolism in visual association areas of the brain in subjects with visual hallucinations has been demonstrated in PET and functional MRI studies [64,71]. This is similar to findings in patients with dementia with Lewy bodies [72].