Dementia

Core

Introduction

Dementia is an umbrella term for a syndrome that presents with cognitive and behavioural symptoms. It is defined as a progressive decline in higher cortical function such as memory, intellect, and personality which ultimately results in a loss of ability to cope independently with activities of daily living, and with a clear consciousness. Depending on the age at which it first presents, dementia is described as early or late onset, with 65 years old being the threshold between the two (source). However, the onset of symptoms can be very subtle and is often insidious, making it difficult to pinpoint a particular time of onset; the age of onset is usually tracked back once a diagnosis is made.

The main cognitive areas that are affected in dementia are memory, orientation, learning capacity and judgement. Patients often struggle with short term memory (although long term memory loss also happens much later down the line).

In terms of non-cognitive symptoms, there is a wide array of different ways these can manifest depending on the underlying pathology. It can be through behavioural symptoms such as increased agitation, aggression, sexual disinhibition or wandering. Patients can show signs of depression and anxiety or sleeping problems such as insomnia and daytime drowsiness. Finally, it can also be accompanied by psychotic symptoms such as visual and auditory hallucinations and persecutory delusions.

Diagnosis

Dementia is a diagnosis of exclusion. It is important to rule out any organic causes for the cognitive and behavioural symptoms before diagnosing dementia.

Some examples of organic disturbances which can have similar presentations include hypothyroidism, hypercalcaemia, vitamin B12 deficiency or normal pressure hydrocephalus, meaning patients in whom a diagnosis of dementia is being considered will usually require blood tests and may require a CT head scan, depending on clinical features.

After any such organic causes have been ruled out, if progressive cognitive decline still persists resulting in an impairment in carrying out activities of daily living along with a clear consciousness, dementia can be diagnosed.

Types of Dementia

There are different types of dementia depending on the pathophysiology underlying the presentation. Some of the most common ones are:

• Alzheimer’s disease
• Vascular dementia
• Lewy body dementia
• Frontotemporal dementia
• Rarer forms of dementia

Alzheimer’s Disease

Alzheimer’s Disease is the most common form of dementia in the UK, making up around 60% of diagnosis, though it is rare under 65 years of age (source). Characteristic changes can be found both macro- and microscopically.

Macroscopic changes include global atrophy of the brain, resulting in sulcal widening and enlargement of the ventricles, particularly the lateral ventricles.

Characteristic microscopic changes include senile plaques of Aβ protein (a by-product of amyloid precursor protein (APP) breakdown) and neurofibrillary tangles made of hyperphosphorylated Tau proteins. This ultimately results in increased neuronal death that occurs in a constant declining pattern.

Vascular Dementia

Vascular dementia is the second most common type of dementia in over 65s (source), and is a result of pathological cerebrovascular events, such as strokes and repeated transient ischaemic attacks.

Risk factors for vascular dementia include history of stroke, hypertension, hypercholesterolaemia, diabetes and smoking.

Vascular dementia usually presents in a stepwise progression, where the patient is stable for a period then undergoes a steep decline following a cerebrovascular event. It can also present with focal neurological symptoms depending on the cortical area affected by infarction.

Importantly, vascular dementia can often be found alongside Alzheimer’s disease, which is known as mixed dementia.

Lewy Body Dementia

Lewy Body Dementia is a broader term for a condition caused by the deposition of Lewy bodies (spherical intracytoplasmic deposits of aggregated α-synuclein protein) in the substantia nigra, temporal lobe, frontal lobe and cingulate gyrus.

Lewy Body Dementia typically presents with fluctuation in cognition and alertness, vivid visual hallucinations, repeated falls, and features of Parkinsonism.

Depending on the timing of the cognitive symptoms with regard to Parkinsonian features, patients are classed with Dementia with Lewy Body (DLB) or Parkinson’s Disease Dementia (PDD). In DLB, cognitive decline occurs before or within a year of parkinsonism (tremor, muscle stiffness, etc.), whereas in PDD, cognitive symptoms appear over a year after the onset of parkinsonism. Pathophysiology of both is very similar and they are both classed as Lewy Body dementias.

Finally, it is important to be very cautious with antipsychotics if Lewy body dementia is suspected, as there is an increased risk of severe antipsychotic sensitivity reactions, including neuroleptic malignant syndrome. This is a medical emergency characterised by fever, confusion, rigidity, raised creatinine phosphokinase and autonomic instability. Any use should be under specialist guidance.

Frontotemporal Dementia

This is the second most common cause of early-onset dementia (source) and is caused by deposition of Pick Bodies in the frontal and temporal lobes. Presentation will mimic lobe dysfunction with loss of inhibition, loss of motivation (without other signs of depression), non-fluent aphasia, inappropriate social behaviour, and repetitive behaviours.

Rarer Forms of Dementia

HIV-associated neurocognitive disorder (formerly AIDS complex dementia)

With an increase in life expectancy of patients living with HIV/AIDS, there is an increase in prevalence of ADC. This happens when HIV infected macrophages enter the brain, and their deposition causes indirect damage to neurones. Generally, onset is insidious, but it progresses rapidly. Characteristics include cognitive impairment, psychomotor retardation, tremor, ataxia, dysarthria, and incontinence.

Creutzfeldt-Jakob disease (CJD)

CJD is a rare condition caused by an infectious protein called a prion. These can be sporadic (due to protein malformation in the brain), variant (caused by bovine spongiform encephalopathy, or mad cow disease), or inherited.

It causes symptoms of memory problems, changes in personality, and problems with balance, vision, mobility, and speech. Most patients with CJD will die within a year of diagnosis as there is no treatment.

Pugilist Dementia

Pugilist dementia is a serious form of brain damage resulting from repeated concussions, and so is common in professional athletes (classically boxers, as shown by the name) or military personnel.

Management

There is currently no cure for dementia and management primarily involves symptom management and, in some cases, slowing disease progression. Management of dementia requires a holistic approach, encompassing the biological, psychological, and social implications of the disease.

Pharmacologically, acetylcholinesterase inhibitors (such as donepezil, rivastigmine and galantamine) have been shown to improve cognition in mild to moderate Alzheimer’s disease. NMDA antagonists (such as memantine) are also used to reduce overstimulation of glutamate activity in Alzheimer’s disease.

Social management needs to be timely and comprehensive: the disease should be explained to the patient in a sensitive way and support provided after appropriate assessment of capacity. Talks regarding investigations such as genetic mapping to inform any relatives of genetic predispositions, ability to carry on driving a car or managing financial resources etc. Power of attorney decisions should be discussed early on as this needs to be done while patient is deemed to have capacity to make such choices. Appropriate care and management plan should be put in place to anticipate care needs and respite care where required.

Edited by: Dr. Maddie Swannack

Reviewed by: Dr. Thomas Burnell

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