Cognitive impairment is probably the last great taboo subject in advanced neuro- logical disease. While it is usually acceptable to patients and families to talk about dysarthric speech, hallucinations, and even incontinence, it is often especially
painful to acknowledge the presence of cognitive problems. Yet changes in the abil- ity to think and reason normally, with the associated effects on behavior and even personality, are common in neurological diseases.
However, if cognitive impairment is present, it is important to recognize it. It can affect the person’s capacity to make wise choices for themselves, making them par- ticularly vulnerable.
Some neurological diseases particularly predispose to cognitive problems. While each disease may be associated with characteristic patterns of cognitive impairment, there is considerable scope for variation between individuals.
How Common Is Cognitive Impairment and What Form Does It Take?
Multiple Sclerosis (MS)
Overall, some degree of cognitive impairment is said to occur in up to 65 % of people with MS [ 5 ] . In one large cross-sectional study, even in patients with early disease and mild physical disability, over half had some degree of cognitive impairment on objective testing. Almost a quarter were frankly cognitively impaired.
Unfortunately too, once cognitive symptoms are established, spontaneous improvement is unusual [ 6 ] . There is an apparent association between the volume of disease on MRI scans of the nervous system and the likelihood of cognitive impair- ment [ 7 ] .
In MS, the typical pattern of cognitive impairment is often the dif fi culty in learn- ing new facts. Taking longer to process information [ 8 ] may be particularly evident in conversation and memory, and verbal fl uency may be affected [ 8 ] . Formal means of assessing cognitive impairment in MS have been described [ 8, 9 ] but are not commonly used in practice.
Parkinson’s Disease (PD)
There are problems with “executive” function, including planning even simple activities and following them through. Setting out the cutlery for a simple meal may assume considerable dif fi culties. Behavioral features with depression and apathy are also common. Hallucinations often feature prominently, although they may respond to subtle changes in medication, as dopamine-binding drugs, including levodopa, may exacerbate hallucinations [ 10 ] . Even in early PD, problems have been identi fi ed with planning and initiating activity, slowness in problem solving, and adapting to new situations [ 11 ] .
Dementia in Parkinson’s Disease
The incidence of dementia in PD is increased up to six times, with up to 30 % of people affected. PD-associated dementia is commoner with increasing age and with the akinetic-rigid form of the disease [ 10 ] . A key feature of PD dementia is the fact that the person has dif fi culty with everyday living because of cognitive de fi cits, independent of any other problems arising from the disease [ 11 ] . Dementia in PD is also characterized by problems with attention and memory problems. There are speci fi c diagnostic tests to be used for PD-associated dementia [ 11 ] .
Signi fi cantly, a large placebo-controlled randomized trial has shown that the dual cholinesterase inhibitor drug rivastigmine may give some improvement in mild to moderate dementia associated with Parkinson’s disease [ 12 ] .
Motor Neurone Disease (MND)
Historically, it was always assumed that cognitive change was very uncommon in MND. However, in one study involving 279 patients with MND, some degree of cognitive impairment (usually involving the frontal lobes) was reported in over 50 % of the patients [ 13 ] . Characteristically, problems arise with planning activities, learning new things, and using language [ 14 ] . Carers of people with MND have described self-centeredness and reduced concern for the feelings of others, while other patients were reportedly more irritable [ 15 ] . Emotional lability affects some patients, while others have blunting of emotions. Sometimes, families and even pro- fessional carers may underestimate or fail to recognize cognitive problems [ 16 ] .
A small minority of people who have MND may have frontotemporal dementia prior to the onset of the physical symptoms of MND. In these cases, the dementia tends to progress particularly rapidly [ 17 ] .
Progressive Supranuclear Palsy (PSP)
Cognitive changes in PSP include forgetfulness and dramatically slowed informa- tion processing speed [ 18 ] . The combination of severely slowed information pro- cessing and marked problems with executive function is characteristic of PSP and differentiates it from other dementias. Furthermore, executive dysfunction appears early in the course of the disease and is relatively severe.
How Might We Respond to Cognitive Impairment?
Recognizing the possibility of cognitive changes and eliciting this objectively is the fi rst step. It is known too that cognitive impairment may be variable over short
periods of time, sometimes even in the same day, as is commonly the case in mul- tiple sclerosis. Such an individual may be lacking in insight, with impaired memory and verbal fl uency in the morning, for instance. At some other time in the day, they may initiate topics of conversation and be alive with dry humor.
Crucially, if it is known that the particular disease puts the individual at risk of cognitive change, then discussions can be facilitated before losing mental capacity.
Speci fi cally, knowing what the person might feel about the common life-prolonging treatments may ensure that their choices are met. This may prevent professionals from subsequently “doing things to the person” passively, contrary to their actual wishes. Likewise, knowing their preferred place of care and death might enable plans to be put in place to achieve this for them.
It is important to recognize the toll which caring for a cognitively impaired patient may impose and that carers often face a distressing and isolating time.
Supporting family and informal carers who may be physically and emotionally exhausted is essential – see Chap. 3 . They may particularly value “time-out” away from the responsibilities of coping with the patient. Sometimes the knowledge that there will be short periods of respite care for the person with the disease may enable carers to continue in their role for longer.