Demystifying Cognitive Impairment Assessment

Written on the 28 March 2022 by Dr Kailas Roberts

One thing that has repeatedly struck me in my years working with people with dementia and their loved ones and carers is that the process of evaluating cognitive impairment, including dementia, is somewhat of a mystery to those I see.                    

Sometimes, this uncertainty about the process means there is a delay in them seeing me or other specialists, and this is a problem as early diagnosis of dementia is important. Many of the interventions that we have that can help alleviate the symptoms of dementia are more effective early, and a prompt diagnosis allows people to plan and avoid potential crises later down the track.

So, here is the lowdown on the process of evaluation. Every specialist is somewhat different in the practice, of course, there are several common elements.

Diagnosing dementia is essentially a clinical process, one that comes about from asking questions and examining the person. It is an unfortunate fact that many people with dementia may minimise the impact of their cognitive symptoms. Sometimes this relates to pour insight – they are genuinely not aware of their difficulties (this is itself a symptom of dementia). Other times, it relates to a process of denial, with fear about the potential ramifications of having dementia meaning that the whole truth is not provided.

This means that it is far preferable to have someone accompany the person with the difficulties. This allows collateral information to be gathered. Often, a spouse or adult child may provide details of cognitive and functional difficulties that are critical in diagnosing a form of dementia. As you can imagine, this can be a delicate process, and it’s not unusual for me to see a degree of conflict between the person with the
cognitive impairment and those caring for them. Nonetheless, it is important to understand the full picture.

Because dementia is not just about memory loss, different aspects of thinking should be asked about by your treating doctor.  These include language skills, visuopatial skills, difficulties with calculation, attention and concentration, and executive skills. Psychological and behavioural changes can also be part of dementia-sometimes the most prominent part – and should also be enquired about. The impact on your day-to-day functioning is also important to establish. Unless there is impairment in this regard, dementia should not be conclusively diagnosed.

There should then be cognitive testing. This will be adapted according to the initial evaluation of the problems. Sometimes, it is obvious that a person is significantly impaired, and in these cases, only a short amount of testing may be required. For others, the impairment may be subtle, and they may require more lengthy testing. The gold standard of testing is something called a neuropsychological assessment. This can take a number of hours to complete but gives a very comprehensive picture of the difficulties. Neuropsychological testing is only required in the minority of cases, however.

Investigations are also an important part of the “work up” of someone with possible dementia. A number of blood tests should be performed, in large part to rule out reversible causes of cognitive impairment, of which there are many.

Personally, I also think everyone should have some form of neuro imaging - a brain scan essentially. Ideally, this should be an MRI brain scan, though if this is not available, then at least a CT brain scan. The former gives much more detail about areas of brain shrinkage and impaired blood supply and can be very helpful in determining what the underlying cause of dementia might be.

Imaging has come a long way in the last two decades, and it is now possible to obtain so-called “functional” scans. These look at the activity of the brain rather than the structure, and again can be helpful at determining the type of dementia. These are known as PET scans and SPECT scans.

Diagnosing dementia is therefore a process that involves several strands. Although it may seem involved, most people do you not find it especially onerous, and as mentioned, it is important to have things evaluated sooner rather than later if possible.