Chapter 3 – Young-Onset Dementias




Abstract




Dementia is stereotypically associated with older people. However, it can affect people in their forties and fifties, or even younger. Currently, even among healthcare professionals, there is a lack of awareness and a dearth of appropriate services for such patients. Despite the attention given to this condition by National Institute for Health and Care Excellence (NICE) guidelines, provision of specialist young-onset dementia services in the United Kingdom (UK) remains patchy. Carers and patients often find themselves being passed ‘from pillar to post’ between psychiatry and neurology, and also between adult, old age and liaison psychiatry. The responsibility for identifying available and appropriate help is often left with carers. This leads to unnecessary delays, causes undue distress to patients and places an added burden on carers. The aim of this chapter is to review how things are in the field of young-onset dementia and provide an overview of this important topic.





Chapter 3 Young-Onset Dementias


Kate Jefferies and Niruj Agrawal



Introduction


Dementia is stereotypically associated with older people. However, it can affect people in their forties and fifties, or even younger. Currently, even among healthcare professionals, there is a lack of awareness and a dearth of appropriate services for such patients. Despite the attention given to this condition by National Institute for Health and Care Excellence (NICE) guidelines, provision of specialist young-onset dementia services in the United Kingdom (UK) remains patchy. Carers and patients often find themselves being passed ‘from pillar to post’ between psychiatry and neurology, and also between adult, old age and liaison psychiatry. The responsibility for identifying available and appropriate help is often left with carers. This leads to unnecessary delays, causes undue distress to patients and places an added burden on carers. The aim of this chapter is to review how things are in the field of young-onset dementia and provide an overview of this important topic.


Young-onset dementias are a fascinating group of disorders that present challenges in diagnosis, management and service provision. It has become accepted practice that ‘young-onset’ refers to dementias that occur before the age of 65 years.


ICD–11 defines dementia as follows:



Dementia is an acquired brain syndrome characterized by a decline from a previous level of cognitive functioning with impairment in two or more cognitive domains (such as memory, executive functions, attention, language, social cognition and judgment, psychomotor speed, visuoperceptual or visuospatial abilities). The cognitive impairment is not entirely attributable to normal aging and significantly interferes with independence in the person’s performance of activities of daily living. Based on available evidence, the cognitive impairment is attributed or assumed to be attributable to a neurological or medical condition that affects the brain, trauma, nutritional deficiency, chronic use of specific substances or medications, or exposure to heavy metals or other toxins.1


The diagnosis of dementia involves a decline in cognitive functions sufficient to impair activities of daily living. It should also be remembered that dementias, particularly in younger people, often present with symptoms other than memory decline as the predominant feature.



Differences between Young-Onset Dementias and Dementias in Later Life


Young-onset dementia is less common than dementia in later life. The differential diagnosis is broader and younger people are more likely to have a rarer form of dementia, as explored in Chapter 4. Both the diagnosis and the symptoms of the condition can have a devastating impact on patients, carers and their families. Younger people are likely to have different needs and commitments to older people. They are more likely to be in work at the time of diagnosis, have dependent family or children, and have heavy financial commitments (e.g. a mortgage). They are also likely to be physically fit and active, and aware of their problems. As a consequence, they are prone to feel distressed and frustrated. Yet access to information and support can be difficult and limited. Spouses of patients with young-onset dementia have many concerns, especially worries about financial and health matters, a feeling of lack of support and social isolation.2



Prevalence of Young-Onset Dementia


In 1998, an estimated 18,500 people had young-onset dementia in the UK.3 The disorder was more common in men than in women: in people between 30 and 64 years of age there were 78.2 cases per 100,000 men and 56.4 cases per 100,000 women. Prevalence increased sharply with age, with two-thirds of patients aged 55 and over (see Figure 3.1). About a decade later, Knapp & Prince reported a comparable prevalence, with young-onset dementias accounting for 2.2% of all people with dementia in the UK.4 They calculated that there are at least 15,034 people with young-onset dementia. In 2013, this estimate had risen again, to suggest there were 42,325 people with young-onset dementia in the UK.5 However, this estimate is based on the number of referrals to services, and the true figure may be up to three times higher.





Figure 3.1 Prevalence of dementia by age Data derived from Harvey R. Young Onset Dementia: Epidemiology, Clinical Symptoms, Family Burden, Support and Outcome. Dementia Research Group, 1998.



Diagnosis of Young-Onset Dementia



Distribution of Diagnoses


The distribution of diagnoses of dementia differs dramatically between older and younger patients. Alzheimer’s disease (AD) is the most common cause of dementia in both groups, accounting for almost two-thirds of cases in older people, but only a third of cases in younger people. Frontotemporal dementia (FTD) occurs much more commonly in younger than in older populations. Rarer causes of dementia also occur with greater frequency in the younger population (see Chapter 4).



Clinical Approach to Assessment


Assessment requires input from the multidisciplinary team. Early diagnosis is essential for a number of reasons: so that early treatment can be provided; to enable the person and family to come to terms with the illness; to allow early access to the correct support; and so that appropriate plans for the future can be made.


Clinically, the focus is on identifying young-onset dementia accurately and on differentiating it from illnesses that can also cause cognitive impairment and mimic dementia. The differential diagnosis of young-onset dementia includes various neurological illnesses, psychiatric illnesses, traumatic brain injury and drug misuse (see Box 3.1), along with some of the rarer causes of dementia explored in Chapter 4.




Box 3.1 Differential diagnosis of young-onset dementia




  1. 1. Delirium



  2. 2. Amnesic syndromes:




    • Korsakoff’s syndrome



    • anoxic brain damage



    • herpes simplex encephalitis




  3. 3. Mild cognitive impairment



  4. 4. Pseudodementia:




    • depressive



    • dissociative




  5. 5. Traumatic brain injury



  6. 6. Neurological illness (e.g. normal-pressure hydrocephalus, stroke, encephalitis, vasculitis, multiple sclerosis)



  7. 7. General medical conditions (e.g. endocrine, B12 deficiency, systemic lupus erythematosus, sarcoidosis)



  8. 8. Drugs (e.g. alcohol, benzodiazepines)



History


History should be obtained from the patient and collateral information should be gathered from an informant such as a family member. An informant’s account is often the key to an accurate diagnosis. Particular areas to concentrate on during history-taking are onset and evolution of symptoms, pattern of deficits, fluctuations in mental state, past or present neurological symptoms, current psychiatric symptoms, past psychiatric symptoms, medical history, family history, use of drugs and alcohol, and risk assessment.



Cognitive Testing


Detailed neuropsychological testing is an important component of the diagnostic process. It can reveal the precise nature and location of the cognitive deficits. Neuropsychological testing can also help in teasing out whether there has been any progression of dementia. Using a series of psychological tests, the neuropsychologist establishes the cognitive abilities of the person and compares them with the person’s estimated best levels and with those for an average person of the same age. Neuropsychological assessment can also identify where a person’s abilities are preserved so that they can be maximized.


Basic bedside testing is also helpful in confirming the nature, degree and location of deficits. The Mini-Mental State Examination (MMSE)6 has been a widely used screening test for cognitive impairment (but see Chapter 11). It is short, easy to use, has high interrater reliability and is useful for monitoring illness progression. However, it is insensitive to frontal lobe disorders, does not detect focal cognitive deficits and is strongly influenced by previous intelligence quotient (IQ) and education. The Addenbrooke’s Cognitive Examination was developed as a more comprehensive screening instrument that also tested frontal lobe functioning.7 It contains a 100-point test battery that assesses six cognitive domains and takes about 15 to 20 minutes to complete. It included the MMSE, but since 2001 the MMSE has not been available without payment of a fee. A subsequent edition of the test, the ACE-III, developed in 2012, does not include the MMSE.8


Bedside tests of frontal lobe functioning, which will often be useful in suspected young-onset dementia, are described in Table 3.1.




Table 3.1 Bedside tests of frontal lobe function








































Test Example Findings indicative of impairment
Verbal fluency ‘Name as many words as you can beginning with the letter T, any words except names of people or places’ Fewer than 13 words a minute
Similarities ‘In what way are a banana and an orange alike?’ Inability to identify the similarity
Cognitive estimates ‘How tall is the tallest man?’ ‘How fast can a horse gallop?’ Estimates will be inaccurate and often wildly wrong
Proverb interpretation ‘What do you understand by the saying “too many cooks spoil the broth”?’ Concrete (literal) not figurative responses
Luria hand sequence Fist–edge–palm (the patient is asked to tap the table with a fist, open palm and side of open hand, and to repeat the sequence as quickly as possible) Inability to follow the sequence; perseveration
Conflicting instructions ‘Tap twice when I tap once, and tap once when I tap twice’ Copying the tapping pattern of examiner rather than doing opposite despite clear instruction
Go/No-Go test ‘Tap once when I tap once. Do not tap when I tap twice’ Tapping twice when the examiner taps twice


Physical Examination


Physical examination is important both in reaching the diagnosis of the subtype of dementia and in identifying any treatable comorbidity. The physical examination is often normal in the early stages of dementia, but the presence of certain symptoms and signs will arouse suspicion of a primary neurological disorder. These include sudden onset of symptoms, focal neurological findings early in the illness, visual hallucinations, incontinence, ataxia and early seizures.


In AD, patients are typically physically well with no neurological signs in the early stages. Later, there may be akinesia and rigidity. In FTD, neurological signs are also usually absent in the early stages. In later stages of the disorder there may be evidence of primitive reflexes, and with further disease progression there may be akinesia and rigidity. Spontaneous features of parkinsonism are one of the core features of dementia with Lewy bodies (DLB). Huntington’s disease is evidenced by the presence of chorea and other pyramidal symptoms. In Creutzfeldt–Jacob disease, myoclonus and other extrapyramidal symptoms are often present.



Further Investigations


When arranging for further investigations the priorities are to identify treatable causes of dementia and to guide accurate diagnosis.


We would suggest conducting the following investigations routinely: full blood count; erythrocyte sedimentation rate; C-reactive protein; renal, liver and thyroid function; vitamin B12 and folate levels; bone profile; lipid profile; glucose; and structural neuroimaging by CT or MRI. Syphilis serology should be tested if there is a history of multiple unprotected sexual contacts and electrocardiogram (ECG) or chest X-ray should be carried out as determined by the clinical presentation, for example a history suggesting treatable comorbidities such as atrial fibrillation.


Structural neuroimaging should be carried out to exclude other pathologies and to help establish the subtype of dementia. MRI is preferable, as CT may not show focal atrophy well (but see Chapter 13 for further discussion of neuroimaging options). Functional imaging may be helpful in the detection of focal brain dysfunction. Hexamethylpropyleneamine oxime (HMPAO) single-photon emission computed tomography scan (SPECT) could help to differentiate the subtype of dementia. Dopaminergic iodine-123-radiolabelled SPECT (DaTscan) can be used to confirm suspected DLB.


In atypical presentations, particularly when dementia is rapidly progressive with features of encephalopathy or focal neurological signs, patients should be referred for neurological opinion; lumbar puncture may be required. Additional investigations such as human immunodeficiency virus (HIV) testing and CD4 count may be considered, depending on the clinical presentation.



Causes of Young-Onset Dementia


The clinical presentations of the following diseases generally do not differ between older and younger populations.



Alzheimer’s Disease


AD accounts for almost a third of young-onset dementia cases. The typical presentation of AD includes progressive episodic (day-to-day) memory loss and visuospatial and perceptual deficits, but well-preserved language and social functioning. The posterior cortical variant of the disease, with prominent impairment of parietal lobe functions, is more common in younger people.


AD is more common in women than men. Prevalence increases with increasing age. The average duration of illness is eight years. Alzheimer’s disease mostly occurs as a sporadic disorder, even in the younger population. However, inherited forms are more likely in the younger population.


Inheritance is autosomal dominant. There are many reported genetic mutations, but there are three genes that are most commonly affected: the presenilin 1 gene on chromosome 14, β-amyloid precursor protein on chromosome 21 and the presenilin 2 gene on chromosome 1.9

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Sep 27, 2020 | Posted by in PSYCHIATRY | Comments Off on Chapter 3 – Young-Onset Dementias
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