What is the step-by-step process for diagnosing dementia?

Step-by-Step Guide to Diagnosing Dementia

The diagnosis of dementia requires a systematic, evidence-based approach that includes comprehensive history taking, cognitive assessment, physical examination, laboratory testing, and neuroimaging to identify cognitive decline that interferes with daily functioning and represents a decline from previous levels. 1, 2

Step 1: Initial Assessment and History Taking

• Collect detailed information about cognitive concerns, including onset (gradual vs. sudden), progression pattern, and specific domains affected (memory, language, executive function, etc.) 2
• Obtain corroborative history from a reliable informant about changes in cognition, function, and behavior, which is essential for accurate diagnosis 2, 3
• Document impact on instrumental activities of daily living (managing finances, medications, transportation, household tasks) 2
• Assess for risk factors including family history, vascular risk factors, and prior head trauma 3
• Review medication list for drugs that may cause cognitive impairment 1
• Evaluate for recent life stressors, sleep disturbances, and mood changes 3

Step 2: Cognitive Assessment

• Use standardized cognitive screening tools:
  • Mini-Mental State Examination (MMSE) - high sensitivity for moderate dementia 1, 2
  • Montreal Cognitive Assessment (MoCA) - more sensitive for mild cognitive impairment 1, 2
  • Clock Drawing Test - useful supplementary screening tool 2, 3
• Assess multiple cognitive domains:
  • Memory (ability to learn and recall new information) 4
  • Executive function (reasoning, judgment, problem-solving) 4
  • Language (word finding, comprehension, naming) 4
  • Visuospatial abilities (object recognition, spatial orientation) 4
  • Personality and behavior changes 4

Step 3: Physical and Neurological Examination

• Perform a comprehensive physical examination with attention to:
  • Vital signs (including orthostatic blood pressure) 4
  • Cardiovascular assessment (carotid bruits, arrhythmias) 4
  • Neurological examination (focal deficits, extrapyramidal signs, gait) 4
• Look for physical findings that may suggest underlying medical issues contributing to cognitive symptoms 4

Step 4: Laboratory Testing

• Recommended core laboratory tests include:
  • Complete blood count 2, 5
  • Comprehensive metabolic panel 2, 5
  • Thyroid function tests 2, 5
  • Vitamin B12 level 2, 5
  • Folate level 4
  • Glucose level 2
  • Calcium level 2
• Consider additional testing based on clinical suspicion:
  • Syphilis serology 5
  • HIV testing (in at-risk populations) 5
  • Urinalysis (to rule out infection) 5

Step 5: Neuroimaging

• Anatomical neuroimaging (MRI preferred over CT) is recommended, particularly when:
  • Onset of cognitive symptoms is within the past 2 years 2, 3
  • Unexpected decline in cognition/function 2, 3
  • Recent significant head trauma 2, 3
  • Unexplained neurological manifestations 2, 3
  • Significant vascular risk factors 2, 3
• MRI is superior for detecting vascular lesions, atrophy patterns, and other structural abnormalities 3

Step 6: Specialized Testing (When Indicated)

• Consider neuropsychological testing when:
  • Patient presentation is complex or symptoms are mild/unusual 2
  • Patient has educational extremes or language/cultural considerations 2
  • Screening tests are normal but clinical suspicion remains high 6
• Advanced biomarker testing may be considered in select cases:
  • CSF analysis for amyloid-beta and tau proteins 4
  • Amyloid PET imaging according to appropriate use criteria 4
  • Genetic testing for patients with early onset (<65 years) or strong family history 4

Step 7: Diagnostic Formulation

• Apply diagnostic criteria for dementia:
  • Cognitive or behavioral symptoms interfere with ability to function 4
  • Represent a decline from previous levels of functioning 4
  • Not explained by delirium or major psychiatric disorder 4
  • Cognitive impairment detected through history and objective assessment 4
  • Impairment in at least two cognitive domains 4
• Determine dementia subtype based on clinical features and test results:
  • Alzheimer's disease (gradual onset, prominent memory impairment) 4
  • Vascular dementia (stepwise progression, history of stroke) 4
  • Lewy body dementia (visual hallucinations, parkinsonism, fluctuations) 4
  • Frontotemporal dementia (behavioral changes, language impairment) 4

Step 8: Rule Out Mimics and Contributors

• Evaluate for conditions that can mimic or contribute to dementia:
  • Depression (can cause pseudodementia) 1
  • Delirium (acute onset, fluctuating course) 1
  • Metabolic disturbances (thyroid disease, vitamin deficiencies) 1
  • Medication effects (anticholinergics, sedatives) 1
  • Sleep disorders (sleep apnea) 4
  • Sensory deficits (hearing loss, vision impairment) 4

Step 9: Follow-up and Monitoring

• Schedule follow-up visits every 6-12 months to track disease progression 2, 3
• Use a multi-dimensional approach to monitor:
  • Cognition (repeat cognitive screening tests) 3
  • Functional autonomy (ADL/IADL assessment) 3
  • Behavioral symptoms 3
  • Caregiver burden 3

Common Pitfalls to Avoid

• Failing to obtain corroborative history from an informant 2
• Overlooking potentially reversible causes of cognitive impairment 2
• Attributing symptoms to normal aging without proper evaluation 1
• Using a "shotgun approach" to diagnostic testing rather than a tiered, methodical approach 2
• Diagnostic overshadowing, where symptoms are attributed to pre-existing conditions rather than emerging dementia 4