What is the recommended approach to diagnose dementia in an adult, particularly an older patient?

Diagnosing Dementia in Older Adults

Dementia diagnosis requires a multimodal assessment combining validated cognitive testing (MoCA preferred), structured functional evaluation (FAQ or DAD), and corroborative informant history (AD8 or IQCODE), followed by laboratory workup to exclude reversible causes and brain MRI to identify structural pathology. 1, 2, 3

Step 1: Obtain Collateral History First

• Interview family members or caregivers before examining the patient, as patients with dementia often lack insight into their deficits and cannot reliably self-report decline 4
• Use the AD8 questionnaire (8-item informant interview; scores ≥2 indicate cognitive impairment) or the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) to document changes in memory, personality, behavior, and daily functioning 1, 2, 4
• Probe specifically for: onset and progression of symptoms, changes in medication management, financial handling, meal preparation, driving ability, and personality/behavioral changes 1

Step 2: Administer Validated Cognitive Testing

• Use the Montreal Cognitive Assessment (MoCA) as the primary screening tool because it is more sensitive than MMSE for detecting mild cognitive impairment and early dementia 1, 2, 3
• MoCA scores <26 indicate objective cognitive impairment; scores of 27/30 suggest possible MCI requiring further investigation 1
• If MoCA is unavailable, validated alternatives include: Mini-Cog (3-item recall + clock drawing, ~3 minutes), Saint Louis University Mental Status (SLUMS), or Rowland Universal Dementia Assessment Scale (RUDAS) 1, 4, 3
• A normal cognitive test score does NOT rule out dementia when functional impairment and reliable informant reports indicate decline 4

Step 3: Assess Functional Status Objectively

• Evaluate instrumental activities of daily living (IADLs) using the Pfeffer Functional Activities Questionnaire (FAQ) or Disability Assessment for Dementia (DAD) 1, 2, 4
• Assess specific domains: medication management, financial handling, appointment keeping, meal preparation, transportation use, shopping, and housekeeping 1
• Documented functional impairment in IADLs distinguishes dementia from mild cognitive impairment 2
• Also evaluate basic activities of daily living (bathing, dressing, toileting, feeding) using standardized scales 5, 4

Step 4: Screen for Behavioral and Psychiatric Symptoms

• Administer the Neuropsychiatric Inventory-Questionnaire (NPI-Q) to systematically identify agitation, hallucinations, depression, apathy, disinhibition, and other behavioral symptoms 5, 1, 4
• Screen for depression using the Geriatric Depression Scale (GDS) or PHQ-9, as depression can mimic or coexist with dementia 5, 4
• Early visual hallucinations suggest Lewy body dementia; early personality/behavior changes suggest frontotemporal dementia; predominant memory loss favors Alzheimer disease 4, 6

Step 5: Perform Targeted Physical and Neurologic Examination

• Look for focal neurologic deficits (suggesting stroke/vascular dementia), parkinsonian features (suggesting Lewy body or Parkinson disease dementia), and gait abnormalities (suggesting normal pressure hydrocephalus) 4, 6, 3
• Assess cardiovascular risk factors (hypertension, diabetes, hyperlipidemia) as modifiable contributors to disease progression 4, 3
• Evaluate vision and hearing, as sensory deficits can worsen cognitive performance 5, 3

Step 6: Order Laboratory Tests to Exclude Reversible Causes

Mandatory screening tests include: 1, 2, 3, 7

• Complete blood count (CBC)
• Comprehensive metabolic panel (electrolytes, glucose, calcium, renal function, hepatic function)
• Thyroid-stimulating hormone (TSH)
• Vitamin B12 level
• Folate level

Additional tests based on clinical suspicion: 3, 7

• Syphilis screening (RPR/VDRL) only if clinical suspicion exists
• HIV testing in at-risk populations
• Erythrocyte sedimentation rate (ESR) if vasculitis suspected
• Heavy metal screening if exposure history present

Step 7: Obtain Brain Neuroimaging

• MRI is preferred over CT because of higher sensitivity for vascular lesions, specific atrophy patterns, and rare conditions 5, 3, 7
• If MRI is performed, obtain: 3D T1 volumetric sequence (with coronal reformations for hippocampal assessment), FLAIR, T2 (or susceptibility-weighted imaging), and diffusion-weighted imaging 5
• Neuroimaging is especially important for: recent symptom onset (<2 years), rapid decline, focal neurologic findings, age <65 years, history of head trauma, seizures, cancer history, or symptoms suggesting normal pressure hydrocephalus 5, 6, 3
• Imaging identifies structural causes: stroke, tumor, subdural hematoma, normal pressure hydrocephalus, multiple infarcts, extensive white matter disease 5, 4, 6

Step 8: Synthesize Information and Establish Diagnosis

• Cross-reference findings with DSM criteria for dementia: acquired cognitive decline in multiple domains (memory, language, visuospatial, executive function) sufficiently severe to interfere with social or occupational function 6, 7
• Use NINCDS-ADRDA criteria for Alzheimer disease or clinical criteria for other dementia subtypes (vascular, Lewy body, frontotemporal) 7
• Recognize that in patients ≥80 years, more than one cause of dementia is often present (e.g., Alzheimer disease plus vascular dementia) 8

Step 9: Longitudinal Monitoring

• Repeat the same cognitive instrument (MoCA) every 6-12 months to establish cognitive trajectory and track progression from MCI to dementia 1, 2, 4
• Increase follow-up frequency to every 3-4 months for patients with prominent behavioral symptoms or rapid clinical decline 4
• Serial assessments over time improve diagnostic accuracy and help distinguish true dementia from normal aging or depression 2, 8

Critical Pitfalls to Avoid

• Do NOT rely on a single cognitive test score in isolation; interpret results in the context of functional status, informant reports, and physical examination 4
• Do NOT dismiss borderline MoCA scores (e.g., 27/30) with markedly elevated AD8 scores (e.g., 6/8) as "normal for age"—this discordance strongly suggests real cognitive impairment with functional impact 1
• Do NOT delay comprehensive assessment with "watchful waiting" when cognitive concerns are present, as early diagnosis allows treatment of reversible causes, advance care planning, and potential disease-modifying interventions 1
• Do NOT assume new-onset depression in older adults is purely psychiatric; it may represent an early manifestation of dementia 4
• Structured cognitive tools detect impairment 2-3 fold more effectively than unaided clinical judgment 2

When to Refer to Neurology

• Age <60 years at symptom onset 3
• Severe behavioral disturbances 3
• Unclear diagnosis after initial workup 3
• Atypical presentations: rapid symptom onset, impairment in multiple cognitive domains but NOT episodic memory, or consideration of CSF biomarkers/genetic testing 6