What is the diagnostic approach for dementia?

Diagnostic Approach for Dementia

The diagnosis of dementia requires a methodical evaluation that includes history-taking, cognitive assessment, laboratory testing, and selective neuroimaging to identify cognitive impairment that interferes with daily functioning and represents a decline from previous levels. 1, 2

Core Diagnostic Criteria

• Dementia is diagnosed when cognitive or behavioral symptoms interfere with ability to function at work or usual activities, represent a decline from previous functioning, and are not explained by delirium or major psychiatric disorder 1, 2
• Key cognitive domains to assess include memory, executive function, visuospatial abilities, language functions, and personality/behavior changes 1, 2
• Obtaining corroborative history from a reliable informant about changes in cognition, function, and behavior is essential for accurate diagnosis 1, 3

Diagnostic Assessment Process

Step 1: Clinical History and Examination

• Collect detailed information about cognitive concerns, including onset and progression of symptoms, sleep and mood disturbances, past medical history, family history, medication use, and review of systems 3
• Perform a thorough physical and neurological examination to identify focal neurological abnormalities that might suggest specific etiologies (e.g., stroke) 4
• Assess impact on instrumental activities of daily living (managing finances, medications, transportation, household tasks) 1

Step 2: Cognitive Assessment

• Use standardized cognitive screening tools such as:
  • Mini-Mental State Examination (MMSE) - high sensitivity for moderate dementia 1, 2
  • Montreal Cognitive Assessment (MoCA) - more sensitive for mild cognitive impairment 2
  • Clock Drawing Test - useful supplementary screening tool 1, 3
• Consider neuropsychological evaluation when:
  • Patient presentation is complex or symptoms are mild/unusual 5
  • Patient has educational extremes or language/cultural considerations 5
  • Comorbidities exist that may present as cognitive impairment (sensory impairments, movement disorders, stroke, brain injury, substance abuse, depression, etc.) 5

Step 3: Laboratory Testing

• Recommended core laboratory tests include:
  • Complete blood count 5, 1
  • Thyroid function tests 5, 1
  • Serum vitamin B12 levels 5, 1
  • Comprehensive metabolic panel (electrolytes, kidney and liver function) 5, 3
  • Glucose levels 5, 3
  • Calcium levels 5, 3

Step 4: Neuroimaging

• Anatomical neuroimaging (MRI preferred over CT) is recommended, particularly when:
  • Onset of cognitive symptoms within past 2 years 1, 3
  • Unexpected decline in cognition/function 1, 3
  • Recent significant head trauma 1, 3
  • Unexplained neurological manifestations 1, 3
  • Significant vascular risk factors 1, 3

Tiered Approach to Specialized Testing

• Tier 1: Standard clinical evaluation with cognitive screening and core laboratory tests - sufficient for many patients 5
• Tier 2: Consider specialized testing based on clinical presentation:
  • Neuropsychological evaluation for complex or mild presentations 5
  • Advanced neuroimaging for atypical presentations 5
  • Biomarker testing in select cases (e.g., young onset, rapid progression) 5

Diagnostic Formulation

• The diagnostic formulation should include three components:
  1. Cognitive functional status (mild, moderate, severe impairment)
  2. Characterization of the cognitive-behavioral syndrome
  3. Likely etiology/differential diagnosis 5

Common Pitfalls to Avoid

• Failing to obtain corroborative history from an informant 3
• Overlooking potentially reversible causes of cognitive impairment (depression, medication effects, metabolic disturbances, sleep disorders) 2, 4
• Using a "shotgun approach" to diagnostic testing rather than a tiered, methodical approach 5
• Neglecting to assess for psychiatric conditions that can mimic or exacerbate cognitive symptoms 3, 4
• Focusing solely on neurodegenerative causes while missing potentially treatable conditions 3, 6

Follow-up and Monitoring

• Schedule follow-up visits every 6-12 months to track disease progression 1, 2
• Use a multi-dimensional approach to monitor cognition, functional autonomy, behavioral symptoms, and caregiver burden 1
• Reassess cognitive, functional, neuropsychiatric, and behavioral symptoms at each follow-up 2