Taking the history

Along with cognitive testing, a detailed history is the most powerful tool for the diagnosis of dementia. Of particular interest are the mode of onset of mental dysfunction, the profile and time course of cognitive and behavioural symptoms, the presence of typical features for PD-D,

Table 20.1 Conditions which may mimic dementia in patients with Parkinson's disease (PD)

Worried patients or their families

Mild cognitive impairment of PD


Acute or prolonged confusion (delirium)

Adverse effects of drugs

presence/absence of depressive symptoms, and symptoms and signs of acute confusion. Typically, cognitive impairment due to PD-D has an insidious onset and slow progression. Current medication and recent changes in treatment should be reviewed, in particular administration of drugs known to cause mental dysfunction, such as anticholinergics, along with recently initiated treatments and changes in doses.

PD patients who are destined to develop dementia frequently present typical early symptoms. It is useful to specifically ask for the presence of such features when taking the history from patients and their family members. Changes in the sleep-wake cycle are frequent, including excessive daytime sleepiness, disturbance of night sleep, and brief confusion or transient hallucinations on awakening. Rapid eye movement (REM) sleep behaviour disorder (RBD; dream-enacting behaviour such as speaking, screaming, or movements in sleep) may be seen also in patients without dementia; however, it is more common in patients with dementia, it presents a risk factor for dementia, and it may precede the development of dementia by many years. Prior to overt psychosis, ‘phantom boarder’ phenomenon or a ‘feeling of presence’ may develop, where patients believe that somebody is standing behind them, a shadow has just passed-by, or there is somebody else in the house, although they do not see this person. The development of hallucinations or psychosis shortly after initiating dopaminergic medication may be another early sign of incipient dementia. The presence of visual hallucinations, usually well-formed, coloured objects, insects, animals, or humans should also be specifically asked for. Patients and their families may not volunteer this information because of fear that patients are going ‘mad’, but may admit it when asked. Other early signs include loss of interest, apathy, social withdrawal, forgetfulness, inattentiveness, and difficulties with concentration when reading a book, watching a movie, or following a conversation. Early signs of functional impairment include difficulties in handling personal or family finances and navigating or finding directions especially in unfamiliar, but sometimes also in familiar, environments.

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