People should be what they appear to be

Life is full of things that are not necessarily what they seem to be, and the same applies when diseases mimic each other and make diagnosis difficult. This is particularly true for different dementias, which often show similar and overlapping symptoms.

Diagnosis is currently made by checking patients for ‘key symptoms’ – symptoms found in one dementia only. For example, Alzheimer’s disease patients have memory problems early on in the disease and memory problems are a ‘key symptom’ in the diagnosis of this dementia…but should they be?

Two people

Telling dementias apart is difficult because of overlapping symptoms, such as memory problems. Brain scans provide a clearer idea of which parts of the brain are affected by which dementia.

Recent findings from my group have challenged this notion. We’ve found that patients with a different dementia (frontotemporal dementia) can also have memory problems. Memory problems in frontotemporal dementia were thought to only appear late in the disease, however, our findings show that frontotemporal dementia patients can develop problems with memory at a very early stage and to the same degree as in Alzheimer’s disease. This is a problem for the diagnosis of dementia, as memory problems are not specific to Alzheimer’s disease alone.

Digging deeper into dementia

In a recent study, we explored memory problems in greater detail by investigating specific regions of the brain in people with frontotemporal dementia and people with Alzheimer’s disease. We found that structures deep in the brain (mammillary bodies and fornix) are associated with memory problems in frontotemporal dementia, while more superficial brain regions (temporal cortex, hippocampus) are associated with memory problems in Alzheimer’s disease.

The five major components of our memory circuit and how they are affected by dementia. The memory regions shaded blue are most affected by frontotemporal dementia, the memory region shaded red is more affected by Alzheimer’s disease.

This is important for diagnosis because it suggests that memory problems in the two diseases are caused by damage to different brain regions. When a patient has memory problems, clinicians can use this data to check which brain regions are affected and this will improve the diagnosis of these dementias and make them easier to distinguish. Now that we better understand the source of memory problems in these two dementias, future therapies can be developed to target the different brain regions.

Why does this matter?

Frontotemporal dementia patients may receive an incorrect diagnosis of Alzheimer’s disease if they present with memory problems early in their illness. A correct diagnosis is crucial because potential treatments for these dementias are different, and the impact of the disease on the family and carers varies with each dementia.

Our findings have important implications for the international diagnostic criteria for dementia. These criteria currently state that Alzheimer’s disease has memory problems and frontotemporal dementia does not. We recommend that the criteria be updated as soon as possible as there is a risk of misdiagnosing and incorrectly treating many dementia patients.

Dr Michael Hornberger heads a research group at NeuRA investigating the neural correlates of behaviour and cognition in ageing and neurodegenerative diseases. The title of this blog post ‘People should be what they appear to be’ is a quote from Othello by William Shakespeare.

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