Features of Dementia

The risk factors overlap for the different dementia subtypes, as do the different pathological processes occurring within the brain. However, certain features are found to predominate in each group.

A description of these features and how they contribute to the disease process is provided:

Neurofibrillary tangles

Neurofibrillary tangles are clumps of tau protein.

Tau proteins are required for normal axonal microtubule stability.

Clumping of these proteins, following hyperphosphorylation, causes neurones to fail and die.

Amyloid plaques

Amyloid plaques are deposits of beta amyloid.

The mechanism through which they cause cell death is not fully understood, but may be due to disrupting cell architecture.

Head injury has been shown to increase the amyloid levels within cerebrospinal fluid (CSF), which in turn may be the mechanism by which head injury can predispose to dementia.

An autosomal dominant genotype affecting amyloid precursor proteins has been associated with early-onset AD.

Synaptic loss

Synaptic loss causes death of the neurons.

As progressive connections are lost, widespread atrophy can ensue.

Lewy bodies

Lewy bodies are intracytoplasmic inclusion bodies made of neurofilaments.

They cause cellular dysfunction by displacing cellular contents.

They were first identified by Frederick Lewy in the substantia nigra of patients with Parkinson’s disease, and this finding reflects the overlap of clinical features between Parkinson’s disease and Lewy body dementia.

Cerebrovascular disease

Cerebrovascular disease may be secondary to well known risk factors such as diabetes, hypertension, hypercholesterolaemia and smoking.

Vascular dementia may follow both embolic and haemorrhagic events, multiple lesions or single infarcts.

Pathophysiological features of dementia subtypes are compared Table 1:

Table 1