Dementia Diagnosis: Structured Clinical Approach
Begin with a detailed history from both the patient AND a reliable informant—never rely on patient self-report alone, as patients with dementia lack insight into their deficits—documenting cognitive changes, functional decline in instrumental activities of daily living (IADLs), behavioral symptoms, onset/progression pattern, and risk factors. 1, 2, 3
Step 1: History Taking (Essential First Step)
From Patient and Informant
- Cognitive concerns: Specific domains affected (memory, language, executive function, visuospatial abilities) with onset and progression pattern 2
- Functional impact: Document decline in IADLs such as managing finances, medications, driving, using technology 1
- Behavioral changes: Mood fluctuations, apathy, loss of empathy, socially inappropriate behaviors, compulsive behaviors 1
- Risk factors: Family history, vascular risk factors (hypertension, diabetes, hyperlipidemia), prior head trauma 2
- Medication review: Identify drugs causing cognitive impairment (anticholinergics, benzodiazepines, opioids) 2, 4
Use Structured Informant Tools
- AD8, IQCODE, or ECog for cognitive/functional changes 3
- Lawton IADL Scale for functional assessment 3
- NPI-Q or MBI-C for behavioral symptoms 4, 3
Step 2: Office-Based Cognitive Assessment
Use the Montreal Cognitive Assessment (MoCA) as your primary screening tool—it has superior sensitivity for mild cognitive impairment and early dementia compared to MMSE. 2, 4, 3
Validated Screening Tools
- MoCA: More sensitive for MCI and mild dementia (sensitivity/specificity superior to MMSE) 2, 3
- MMSE: Remains valuable for moderate dementia and longitudinal tracking (sensitivity/specificity >80% for distinguishing dementia) 2, 3
- Mini-Cog or Memory Impairment Screen plus Clock Drawing: For rapid screening 4
Assess Multiple Cognitive Domains
- Memory (acquisition and recall of new information) 1
- Executive function (reasoning, complex tasks, judgment) 1
- Language (word-finding, comprehension, fluency) 1
- Visuospatial abilities (recognition, spatial orientation) 1
- Attention and processing speed 2
Step 3: Physical and Neurological Examination
Perform a comprehensive examination looking specifically for focal neurologic abnormalities suggesting stroke, parkinsonian features (rigidity, bradykinesia, tremor), gait disturbances, and signs of normal pressure hydrocephalus (triad of gait apraxia, urinary incontinence, cognitive impairment). 2, 5
- Vital signs and cardiovascular assessment 2
- Neurological examination for focal deficits, movement disorders, primitive reflexes 2, 5
- Sensory assessment (vision and hearing deficits can mimic or worsen dementia) 1, 4
Step 4: Core Laboratory Testing
Order these tests in ALL patients to exclude reversible causes: 2, 4, 3
- Complete blood count 2, 3
- Comprehensive metabolic panel (sodium, calcium, glucose) 2, 3
- Thyroid function tests (TSH, free T4) 2, 3
- Vitamin B12 level 2, 3
- Folate level 2, 3
Additional Testing Based on Clinical Suspicion
- HIV testing if risk factors present 2, 3
- Syphilis serology if indicated 2
- Erythrocyte sedimentation rate or C-reactive protein if vasculitis suspected 6
Step 5: Neuroimaging
Obtain MRI (preferred over CT) when cognitive symptoms began within the past 2 years, when there is unexpected decline, or to evaluate for vascular lesions, atrophy patterns, and structural abnormalities. 2, 4, 3
MRI is Superior for Detecting
- Vascular lesions (infarcts, white matter disease) 2, 3
- Atrophy patterns (hippocampal atrophy in Alzheimer's, frontal/temporal atrophy in frontotemporal dementia) 2
- Structural abnormalities (subdural hematoma, normal pressure hydrocephalus, tumors) 5
Step 6: Apply Diagnostic Criteria for Dementia
Dementia is diagnosed when cognitive or behavioral symptoms: (1) interfere with ability to function at work or usual activities, (2) represent a decline from previous functioning, and (3) are not explained by delirium or major psychiatric disorder. 1, 3
Cognitive Impairment Must Involve ≥2 Domains
- Impaired memory (repetitive questions, misplacing items, forgetting appointments) 1
- Impaired reasoning/judgment (poor safety awareness, inability to manage finances) 1
- Impaired visuospatial abilities (getting lost, difficulty recognizing faces) 1
- Impaired language (word-finding difficulty, speech errors) 1
- Personality/behavioral changes (apathy, disinhibition, loss of empathy) 1
Step 7: Rule Out Mimics and Contributors
Systematically evaluate for conditions that can mimic or contribute to dementia before finalizing the diagnosis: 2, 4, 3
- Depression (pseudodementia—can mimic or co-occur with early dementia) 1, 3
- Delirium (acute onset, fluctuating course—requires urgent evaluation) 1, 4
- Metabolic disturbances (electrolyte abnormalities, hypoglycemia, B12/folate deficiency, thyroid dysfunction) 1, 3
- Medication effects (polypharmacy, anticholinergics, benzodiazepines) 1, 3
- Sleep disorders (sleep apnea causing cognitive impairment) 1, 3
- Sensory deficits (hearing loss, vision impairment) 1, 4
- Pain (undiagnosed or undertreated pain affecting cognition) 1
Step 8: Determine Dementia Subtype
Based on clinical features and test results: 2, 3, 7
- Alzheimer's disease: Gradual onset, prominent memory impairment, hippocampal atrophy on MRI 3, 5
- Vascular dementia: Stepwise decline, focal neurologic signs, vascular lesions on imaging 3, 7
- Lewy body dementia: Visual hallucinations, parkinsonism, fluctuating cognition, REM sleep behavior disorder 3, 7
- Frontotemporal dementia: Early behavioral changes or language impairment, frontal/temporal atrophy 3, 7
- Parkinson's disease dementia: Dementia onset ≥2 years after Parkinson's diagnosis 8, 7
Step 9: When to Refer to Specialist
Refer expeditiously to a dementia subspecialist for: 1, 4
- Atypical presentations (prominent language/behavioral abnormalities, sensory/motor dysfunction of cerebral origin) 1
- Early-onset dementia (age <65 years) 1, 4
- Rapidly progressive dementia (developing within weeks to months—this is urgent) 1, 4
- Diagnostic uncertainty after initial evaluation 1
- When office-based cognitive assessment is not sufficiently informative (neuropsychological testing may be needed) 1
Step 10: Consider Advanced Testing (Specialist Level)
When diagnostic uncertainty persists after structural imaging: 1
- FDG-PET or CSF Aβ42 and tau/p-tau for evaluating neurodegenerative patterns 1
- Amyloid PET scan according to appropriate use criteria to evaluate for cerebral amyloid pathology 1
- Genetic testing if autosomal dominant family history (involve genetic counselor) 1
Common Pitfalls to Avoid
- Delaying specialist referral for rapidly progressive or atypical symptoms (these require urgent evaluation) 1, 4
- Failing to obtain informant history (patient self-report is unreliable) 1, 3
- Overlooking delirium as a cause of acute cognitive changes (requires urgent medical evaluation) 1, 4
- Not assessing functional abilities (dementia diagnosis requires functional impairment in IADLs) 1
- Missing medication-induced cognitive impairment (review all medications, especially anticholinergics) 2, 4
- Neglecting to assess caregiver burden (significantly impacts patient outcomes and care planning) 4, 3
Management Framework After Diagnosis
Pharmacologic Treatment
- Cholinesterase inhibitors (donepezil, rivastigmine) for mild to moderate Alzheimer's disease 3, 9, 8
- Memantine for moderate to severe Alzheimer's disease (alone or combined with cholinesterase inhibitor) 3, 9
- Rivastigmine for Parkinson's disease dementia 3, 8
Non-Pharmacologic Interventions (Prioritize These)
- Cognitive training, music/art therapy, reminiscence therapy 3
- Physical exercise (walking programs) 3, 5
- Mediterranean diet 3
- Cognitively engaging activities (reading, puzzles) 5
- Socialization (family gatherings, group activities) 5
Longitudinal Monitoring
Schedule follow-up visits every 6-12 months for stable patients (more frequently if behavioral symptoms present) to track: 2, 4, 3