Assessment of behavioural symptoms
At the bedside or in the office setting, the most efficient and practical way to assess behavioural symptoms is through a semi-structured interview with the patient and a well-informed family member. As patients and caregivers may not voluntarily report psychotic symptoms, these should be specifically asked for, in particular the existence of typical symptoms such as infidelity, phantom boarder or ‘feeling of presence’ delusions, and visual hallucinations, typically of insects, animals, or people. A tactful way of asking may be: ‘Patients with this disease may sometimes have dreams when they are awake, does this happen to you?’. Likewise loss of interest and motivation, apathy, social withdrawal, depressive symptoms such as sadness and anhedonia, excessive daytime sleepiness, transient confusion and disorientation on awakening, and symptoms of RBD must be explored.
The most widely used formal scale to assess behavioural and neuropsychiatric symptoms is the Neuropsychiatric Inventory . There are 10- and 12-item versions, and also the possibility to capture caregiver burden. The scale is easy to use with screening questions for each symptom answered by an informed caregiver. When the occurrence of a particular symptom is confirmed the severity is measured semi-quantitatively by assessing the frequency of its occurrence and the grade of discomfort caused by it.
Assessment of functional impairment
This is probably the most difficult part of the assessment, yet the most critical one to ascertain the diagnosis of dementia as per current definitions. It is generally less difficult to decide if a patient has functional impairment. The more difficult part is to judge whether and how much of the functional impairment is due to motor versus mental dysfunction. This can be especially difficult in patients who have severe motor impairment, in particular axial involvement such as postural imbalance and speech disorder, symptoms which are more frequent in PD-D patients. Elderly patients may have stopped taking care of themselves for many years, simply because it is more convenient to rely on their caregivers for ADL. In such cases it may be difficult to judge whether they have any functional impairment as they do not attempt to do much by themselves.
Given all these limitations the most direct and useful way to assess functional impairment is to ask family members what the patient was able to do before cognitive symptoms become apparent that she/he is not able to do anymore. Instrumental (such as handling finances and money, shopping, travelling alone) and basic (such as choosing clothes, dressing, bathing, personal hygiene) ADL, as well as occupational and social activities should be assessed by asking lead-questions. Once newly developed functional impairment is acknowledged, one should attempt to qualify if the impairment is more due to mental or motor dysfunction. Questions for various daily activities should be asked, based on the age, sex, social, and occupational status of the patient. It was proposed that the ability of a patient to organize and remember his/her own medication schedule can be used to assess functional impairment, as all PD patients receive medication . This proposal was validated in a large number of PD patients; although the Pill Questionnaire demonstrated acceptable basic properties as a screening tool for dementia, its positive predictive value was low .
Although there is none specifically developed for PD, ADL scales such as the Alzheimer Disease Consortium Study-Activities of Daily Living (ADCS-ADL) scale  or the Disability Assessment in Dementia (DAD)  scale can be used to quantitatively assess functional impairment.