Types of Dementia

Dementia is a term that is often used broadly to refer to the loss of cognitive abilities, but there are a number of different forms of dementia. Here, we will outline common forms of dementia, as well as the symptoms and brain changes associated with each dementia type.

Alzheimer’s disease

Alzheimer’s disease is arguably the most well recognized form of dementia, likely because it is the most common form. Between 60 and 80% of dementia cases fall into the Alzheimer’s disease category. The disease is marked by memory deficits, depression, and reduced motivation. As the disease progresses, patients have a difficult time communicating well, making effective decisions, and even doing tasks we do not normally think of as highly cognitive, such as walking, speaking, and swallowing.

Alzheimer’s disease is progressive, meaning it gets worse over time, and the worsening of symptoms is mirrored by changes within the brain. In addition to cell damage and death, Alzheimer’s disease involves the accumulation of what are known as plaques and tangles. Plaques refer to a protein fragment called beta-amyloid, whereas tangles occur due to the twisting of a different protein called tau. An abundance of medical research has focused on how to prevent or disrupt the accumulation of plaques and tangles as a way to medically intervene with Alzheimer’s disease, but unfortunately the research has not led to a cure for the disease.

Dementia with Lewy bodies (DLB)

Dementia with Lewy bodies is a form of dementia that has a lot in common with Alzheimer’s disease. However, with this particular type of dementia, patients usually have trouble sleeping, experience hallucinations, and suffer from mobility issues. The issues with movement that those with DLB have are similar to what is experienced in Parkinson’s disease (PD). The overlap in symptoms between DLB and PD is likely due to a similarity in the changes in the brain that occur with these two pathologies. Specifically, in both DLB and PD, Lewy bodies, which are clumps of another protein, alpha-synuclein, are present. In DLB, Lewy bodies develop in the cortex of the brain, whereas they develop in other areas in PD.

Vascular dementia

About 10% of dementia cases are classified as vascular dementia. This type of dementia usually occurs as a result of brain injury, and the specific symptoms vary depending on the location and extent of the injury. The details of the injury are usually determined with brain imaging technqiues, and this determination can provide deeper insight into the likely symptoms and outcomes of vascular dementia patients. Common symptoms associated with vascular dementia are difficulty in planning and decision making.

Mixed Dementia

When someone suffers from more than one type of dementia, their dementia is referred to as “mixed dementia.” Depending on the particular forms of dementia present, these patients experience different symptoms and brain changes.

References

Bouchard, R. W. (2007). Diagnostic criteria of dementia. Can J Neurol Sci, 34 Suppl 1, S11-18.

Raz, L., Knoefel, J., & Bhaskar, K. (2015). The neuropathology and cerebrovascular mechanisms of dementia. J Cereb Blood Flow Metab. doi: 10.1038/jcbfm.2015.164

Storey, E., Slavin, M. J., & Kinsella, G. J. (2002). Patterns of cognitive impairment in Alzheimer’s disease: assessment and differential diagnosis. Front Biosci, 7, e155-184.