Parkinsonism is an umbrella term used to describe conditions that fit the Parkinsonian syndrome including Lewy body dementia, multiple system atrophy, progressive supranuclear palsy and drug-induced Parkinson’s disease, among others. Parkinson’s disease (PD) is one of the most common neurodegenerative diseases. It is characterised by four signs: a resting tremor, bradykinesia, gait disturbance and rigidity. This description clearly focuses on the motor aspects of the disease, as did Dr James Parkinson himself in his original description of PD as the ‘shaking palsy’. However, non-motor signs and symptoms can also play a profound role in the disease progression and burden of Parkinsonism. Dementia is a serious complication of PD that can have a devastating effect on the quality of life of the patients who suffer from it.¹

Dementia syndromes associated with Parkinsonism include dementia with Lewy bodies, PD dementia and PD plus syndromes with dementia. Lewy body dementia is the second most common form of dementia, preceded by Alzheimer’s disease.²

Epidemiology 

Dementia is a much more prevalent problem in the PD population than in the general population. Patients with PD are six times more likely to develop dementia. Hallucinations and loss of self-care skills are common characteristics of dementia in Parkinsonism.³ The prevalence of dementia in idiopathic Parkinson’s diseases is estimated to be around 30% and increases to 75% in those who have been symptomatic for 10 years. Several factors are said to indicate an increased likelihood of developing dementia secondary to Parkinsonism. The main factor to consider is increasing age. Other factors include late onset of motor symptoms of PD, and bradykinesia. The lack of a dominant Parkinsonian tremor, bilateral onset of tremor and a low response to levodopa are other potential predictors for development of dementia.¹ Motor symptoms believed to be mediated by non-dopaminergic mechanisms like gait and posture were recently said to be associated with a more rapid cognitive decline. A 2006 study investigated motor subtypes of PD dementia, PD and Lewy body dementia patients and their cognitive decline. It found that 25% of the PD patients who suffered from postural instability gait difficulty developed dementia during the course of the study.⁴

Features of dementia in Parkinsonism

According to Henderson (1994), “dementia is a syndrome due to disease of the brain, usually of chronic or progressive nature, in which there is a disturbance of multiple higher cortical functions.”³ Dementia syndromes associated with Parkinsonism can present with a variety of different cognitive and behavioural symptoms as well as different time courses. The presentation of Lewy body dementia can vary; notable characteristics include attention deficits, visuospatial difficulties and reduced fluency.²

Lewy bodies are found in up to 25% of autopsies performed in older adults who suffered from dementia. Lewy body dementia patients have been found to have difficulties with spatial and perceptual networks of visual processing. They tend to perform worse than Alzheimer’s disease patients in visual information processing. Visual hallucinations are common in Lewy body dementia, the hallucinations tend to recur and are generally vivid. Hallucinations are usually an early feature of the disease. The four most common psychotic symptoms are visual hallucinations (54%), delusions (49%), auditory hallucinations (25%) and olfactory hallucinations (7%).⁵ Other symptoms include depression, anxiety and aggressive behaviour. Another common feature of Lewy body dementia is REM sleep disturbance, this is usually present early.⁶

PD dementia is associated with impairments in attention, memory and executive function.² PD dementia and Lewy body dementia have similar cognitive and behavioural symptoms. The distinction between the two is a temporal one: if the motor symptoms persist for a year without evidence of cognitive problems before dementia occurs this is termed PD dementia. Lewy body dementia implies that cognitive and motor symptoms present within a year of each other. Another distinction which is sometimes made is that visual hallucinations are much more common in Lewy body dementia.⁵ PD plus syndromes with dementia include progressive supranuclear palsy and cortical basal ganglionic degeneration. They involve cognitive abnormalities and motor difficulties but typically lack tremor.²

Diagnosis of dementia

Diagnosis of dementia requires identification of a cognitive impairment, onset of the impairment, its progression and assessing how much this impairment has impinged on the patient’s daily life. A detailed history is a vital part of the diagnosis of dementia. Consulting with family members or friends of the patient and use of the mini-mental state examination (MMSE) are both of value when investigating dementia. Speaking to people close to the patient is important as sometimes the patient may not notice or complain of a cognitive impairment due to a loss of self-awareness. A score of less of than 24/30 in the MMSE is usually considered suggestive of dementia.²

Although dementia has increasingly been seen as a common feature in patients with PD, particularly in elderly patients, specific diagnostic criteria of dementia associated with PD have been somewhat lacking.⁷ In 2007, a task force from the Movement Disorder Society (MDS) outlined diagnostic criteria for dementia associated with PD. In the study they outlined core features, associated clinical features, features that make the diagnosis uncertain and features that make it impossible to reliably diagnose PD dementia. 

The core features of dementia associated with PD according to the study were as follows: a diagnosis of PD, an impairment in more than one cognitive domain and deficits severe enough to impact on activities of daily living. The associated clinical features discussed were cognitive features such as impaired attention, impaired executive function, impaired visuospatial functions, impaired memory and word-finding difficulties. 

They also discussed behavioural features including apathy, changes in personality or mood, hallucinations, delusions and excessive daytime sleepiness. They proposed that for a probable diagnosis of PD dementia both core features must be present, two out of the four cognitive impairments and one behavioural symptom.⁸ Treatable causes of dementia should be excluded – this is usually done by neuroimaging studies and laboratory tests, eg. vitamin B12 level.

Short screening methods that can be easily administered and are well validated are useful to accurately diagnose PD dementia as detailed neuropsychological testing is not always possible in routine clinical care. The MDS task force also put forward a short check-list which is suitable for bedside use to screen for PD dementia. It is composed of a list of eight items. A study in 2011 sought to validate this check-list. It found that although the MDS check-list was very specific it wasn’t as sensitive as a full neuropsychological evaluation which remains the gold standard for diagnosing PD dementia.⁷ The presence of varying levels of alertness, visual hallucinations and a Parkinsonian syndrome is generally considered a probable diagnosis of Lewy body dementia.²

Management of dementia

The treatment of dementia in Parkinsonism is unfortunately not curative, it aims to delay progression or improve prognosis. Drugs used to treat dementia include acetylcholinesterase inhibitors. Rivastigmine is an example of an acetylcholinesterase inhibitor which has proved to be clinically useful. The adverse reactions associated with rivastigmine include nausea, vomiting, diarrhoea, drowsiness and tremor. As visual hallucinations are a common feature of dementia in Parkinsonism, antipsychotics may also be useful. 

Antipsychotics should be prescribed with caution as, although they may improve non-motor symptoms, they can have a worsening effect on the motor manifestations of PD.⁹ Levodopa and dopamine agonists have been shown to improve cognition as well as psychomotor slowing. The pharmacological treatment available mainly aims to stabilise the patient and slow progression of the disease.⁶

Patients with dementia require long-term management. Standard psychological therapies such as cognitive behavioural therapy may help those with mild-to-moderate dementia to overcome negative thinking and social withdrawal. Managing the behavioural symptoms of dementia can be very difficult. Sometimes environmental factors can trigger behavioural symptoms, in this case the most appropriate intervention may be modifying the patient’s environment. Environmental features that could trigger a patient suffering from dementia include the room layout or size, furniture type or the noise or lighting in the room. Adapting the environment has been found to reduce anxiety and improve emotional wellbeing.⁶ As patients suffering from dementia by definition have cognitive deficits, a key part of their management is determining whether they have the capacity to make their own decisions regarding their medical and financial affairs. 

Impact of dementia

As discussed above the management of dementia in Parkinsonism is complex. Undoubtedly the motor aspects of the disease can affect the patient’s quality of life, however cognitive and behavioural impairment also play a role. Dementia has an impact not only on the patient but also on their family members, caregivers and broader support network.¹⁰

There are several practical issues associated with the management of dementia, particularly as patients become more dependent as the disease progresses. Issues that may need to be addressed are laundry services for soiled linen and provision of a car badge so that the patient can avail of priority parking.¹¹ Dementia has major implications for daily living of patients. Dementia can affect patients’ lives in a number of ways, for example people living with dementia are at greater risk of falls. 

Dementia is associated with the need for nursing home admission. Patients with dementia are also more likely to need hospitalisation; this can have a negative effect on patients, both emotionally and financially.¹² Developing daily routines early on in the disease progression can be useful for the patient. Utilising community day services can give the carer a much-needed break.

To conclude, it would be grossly remiss of the authors not to discuss the role of the caregiver. It is important that society does not forget the hard work carried out day to day. It is recognised that this can put them under pressure, a pressure which clinicians must ensure they can handle. Symptoms such as aggression and agitation can be challenging for caregivers to deal with. Caregivers of patients with dementia can be under significant stress, particularly as symptoms worsen. In England, two-thirds of people with dementia live in the community and the majority of these people are cared for by family members. Carers of people with dementia are more likely to be depressed than those who care for people with conditions. They also report a heavier burden; this may be due to a lack of accessible support. Clinicians need to systematically assess caregivers’ needs as well as those of their patient to ensure that they can cope with the burden of looking after their loved one.¹³

Referring the primary caregiver to a carers’ group for support may be beneficial. Organising regular appointments for the patient with an occupational therapist and arranging visits from district nurses and community psychiatric nurses can also help the caregiver.¹¹

Declaration of interest: none.

References 

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