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Dementia (Diagnosing Dementia (essential symptoms: acquired impairment in…
Dementia
Diagnosing Dementia
essential symptoms: acquired impairment in STM & LTM, impairment in abstract thinking, impaired judgment -> the disturbance is severe enough to interfere with work & usual activities
- definite: clinical diagnosis + histologic confirmation (study of tissue) --> post mortem
- probable (most common one): typical clinical syndrome without histologic confirmation
- possible: atypical clinical features but no alternative diagnosis apparent & no histologic confirmation
laboratory studies:
- thyroid function tests, measurement of serum vitamin B12 level, blood glucose levels, liver function tests, screening for heavy metals --> to identify specific alternative causes
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separation of DLB from PDD:
- long duration of parkinsonian motor syndrome before dementia in PDD
- initial dementia accompanied by extrapyramidal symptoms in DLB
Vascular dementia diagnostic criteria have variable accuracy (multiple classification criteria, also for AD)
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Mild AD can be diagnosed according to clinical criteria with high degree of certainty (more comprehensive NP test battery)
use all available evidence: history, vascular risk factors, physical examination, clinical course, neuroimaging, laboratory data, cognitive imapairment pattern
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Neurobiological markers
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secondary consequences of deposition of beta-amyloid:
- formation of neurofibrially tangles
- oxidation & lipid perodixidation
- glutamatergic excitoxicity
- inflammation
- activation of cascade of apoptopic cell death
AD as Disconnection Syndrome:
- loss of effective interaction between various cortical regions
- neurofibrally tangles situated in cortical layers & cell types that support the connections between association areas
- cortical disconnection leads to abnormalities in interregional pattern of blood flow activation eg. during performance of cognitive tasks
- reduced synchronization between EEG signals at sites that correspond to association areas that should work together during cognitive tasks eg. cross modal stimulus processing
- impaired interaction between visual & auditory cortical systems
- "feature binding" impaired
cell dysfunction & cell death in neurons responsible for maintenance of neurotransmitter systems eg. ACh
overall: neuronal atrophy, synapse loss, abnormal accumulation of plaques & tangles in MTL, frontal, temporal & parietal association cortices
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Diagnostic issues
criteria have good sensitivity but bad specificity: because there are many common features between different types of dementia (overlap)
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normative data issue: we need more longitudinal studies -> in old elderly, there is a mix of normal aging & pathology and it is still not disentangled
MMSE
Advantages:
- requires no specialized equipment of training for administration
- short
- has validity & reliability for diagnosis & longitudinal assessment of AD
Disadvantages:
- difficulty to identify MCI
- age, education, culture, SES can cause bias in scores
- lack of standardization
- lack of suitability for illiterate subjects (highly verbal test)
- multiple testing allows for easy remembering of questions
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examines: orientation, immediate & short-term memory, attention, calculation, language, praxis
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Cognitive markers
asking the same questions repeatedly, getting lost in familiar places, being unable to follow directions, getting disoriented, neglecting personal safety, hygiene & nutrition
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Psychological markers
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psychosis, agitation in middle & late phases
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Syndromal diagnosis: doesn't identify a specific cause, offering a symptomatic relief (diagnoses of mental illnesses) -> you need to look at neuropsychological assessment
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AD & Vascular Dementia
more impairment than AD on executive functions tests but AD individuals are more impaired on tests of episodic memory
Etiological diagnosis: identifying a specific cause, looking at the patient's history, how symptoms develop over time, taking genetic & hereditary factors into account, also medical records
Why should we take patient's history into account?
- to keep track of medications used
- to recognize factors that might contribute to worse outcomes or better outcomes
- to see how the symptoms progress/develop over time
- crucial for etiological diagnosis (basis for neurologists)
- Syndrome is just a state of the patient. It doesn't tell us the cause and progression.