📚 Geriatrics — L4: Cognitive Disorders & Dementia In Elderly

📚 Lecture Overview

This lecture explores cognitive disorders and dementia in the elderly, distinguishing between normal age-related changes, mild cognitive impairment, dementia, and delirium. Understanding these conditions is critical for accurate clinical diagnosis, distinguishing reversible causes from progressive neurodegenerative diseases, and implementing appropriate nonpharmacological and pharmacological management.

🎯 Key Concepts & Definitions

• Working Memory: A limited capacity store retaining information over short periods (seconds to 1-2 minutes) for immediate mental operations.
• Episodic Memory: The conscious recollection of personal events, including specific time, place, and contextual details.
• Semantic Memory: An individual's context-independent knowledge about the world, including vocabulary, facts, and concepts.
• Procedural Memory: Relates to skill learning, including motor, cognitive, perceptual, and "how-to" learning.
• Age-Associated Memory Impairment: Normal cognitive changes with aging featuring a relative deficiency in recall speed that does not affect daily functioning.
• Mild Cognitive Impairment (MCI): Greater memory or cognitive loss than normal aging, but daily functioning is typically preserved.
• Dementia: Chronic, global, usually irreversible deterioration of cognition that impairs daily functioning.
• Delirium: An acute, transient, usually reversible, fluctuating disturbance in attention, cognition, and consciousness level.

📖 Main Content

Memory Systems and Aging

• Memory is divided by storage duration into short-term (working) and long-term memory.
• Short-term memory includes two systems: Phonologic (for verbal information) and Visual-spatial (for visual information).
• Explicit memory includes episodic memory (events with context) and semantic memory (facts and word meanings).
• Implicit memory includes priming (cued recall via prior exposure) and procedural memory (motor and cognitive skills like riding a bike).
• Implicit memory processes remain relatively unimpaired in older adults.
• Short-term memory decline is part of normal aging and does not impact daily functioning.

Mild Cognitive Impairment (MCI)

• Causes greater memory/cognitive loss than age-associated memory impairment.
• Daily functioning is not affected.
• Subtypes include amnestic MCI (primarily affects memory) and nonamnestic MCI (affects other thinking skills like decision-making or visual perception).
• Up to 50% of patients with MCI develop dementia within 3 years.
• No FDA-approved medications currently treat MCI; management focuses on regular exercise, controlling cardiovascular risks, and cognitive/social engagement.

Dementia

• Chronic, global, irreversible cognitive deterioration accounting for over half of nursing home admissions.
• Most common type is Alzheimer disease (60-80% of cases), followed by vascular dementia, Lewy body dementia, and frontotemporal dementias.
• Reversible dementia causes: Normal-pressure hydrocephalus, subdural hematoma, hypothyroidism, vitamin B12 deficiency, toxins, and depression.
• Core Diagnostic Criteria (NIA-AA):
• Symptoms interfere with work or daily activities.
• Decline from previous functioning levels.
• Not explained by delirium or major psychiatric disorder.
• Impairment in $≥ 2$ domains: amnesia, aphasia, agnosia, executive dysfunction/apraxia, and personality/behavior changes.
• Pharmacological Treatment:
• Cholinesterase inhibitors (Donepezil, Rivastigmine, Galantamine): Inhibit acetylcholinesterase to increase brain acetylcholine levels.
• Memantine: NMDA receptor antagonist used to slow cognitive loss in moderate to severe dementia; can be synergistic with cholinesterase inhibitors.
• Antipsychotics / SSRIs: Used for behavioral disorders and depression (avoid sedating/anticholinergic drugs).

Delirium (Acute Confusional State)

• An acute, transient, fluctuating disturbance in attention, cognition, and consciousness level.
• Three subtypes based on consciousness level: Hyperactive (agitation, disruptive behavior), Hypoactive (lethargy, sleepiness), and Mixed.
• Most common causes: Drugs (anticholinergics, psychoactive drugs, opioids), dehydration, and infection.
• Management:
• Correct precipitating factors and remove predisposing factors.
• Provide a stable, quiet, well-lit environment with reorientation cues.
• Low-dose Haloperidol or second-generation antipsychotics for severe agitation.
• Benzodiazepines are strictly reserved for alcohol or benzodiazepine withdrawal; otherwise, they worsen confusion.

📊 Visual Learning

💡 Important Points to Remember

• Short-term memory loss is the hallmark first sign of Alzheimer disease.
• Delirium is acute and fluctuating; Dementia is chronic and progressive.
• Mild Cognitive Impairment (MCI) preserves daily functioning, whereas Dementia impairs daily functioning.
• Up to 50% of MCI patients progress to dementia within 3 years.
• Cholinesterase inhibitors increase brain acetylcholine by inhibiting acetylcholinesterase.
• Memantine is an NMDA antagonist used for moderate to severe dementia.
• Benzodiazepines are the drug of choice only for alcohol/sedative withdrawal delirium; they worsen other forms of delirium.
• Apo $\varepsilon 4$ allele: Having two alleles increases Alzheimer risk by 10 to 30 times, but testing is not recommended for routine diagnosis.
• Depression can mimic dementia (pseudodementia) and frequently coexists with it.
• Agnosia is the inability to identify objects despite intact sensory function; Apraxia is the inability to perform learned motor tasks despite intact motor function.

⚠️ Common Exam Questions

• Classic MCQ Trap: Examiners frequently present an elderly patient with acute confusion post-surgery and offer antipsychotics vs. benzodiazepines. Remember: if the cause is alcohol withdrawal, use benzodiazepines; for general delirium agitation, use antipsychotics (like low-dose haloperidol), as benzodiazepines worsen standard delirium.
• MCI vs. Dementia Trick: A question will describe memory loss in an older adult. If daily functioning is intact, the answer is Mild Cognitive Impairment (MCI) or normal aging. If daily functioning is impaired, the answer is Dementia.
• Reversibility Trap: Questions testing reversible dementias will feature patients with low B12, high TSH (hypothyroidism), or normal-pressure hydrocephalus. Always look for lab values pointing to nutritional or metabolic deficiencies.

📝 Quick Review Checklist

I can explain the differences between explicit, implicit, and working memory
I understand the clinical criteria distinguishing normal aging, MCI, and dementia
I can define the core diagnostic features and subtypes of delirium
I know the mechanisms of cholinesterase inhibitors and memantine
I can identify the most common causes of reversible dementia
I know the correct pharmacological management for delirium based on etiology