Diagnostic Criteria and Assessment for Dementia

Core Diagnostic Requirements

• Dementia diagnosis requires (1) cognitive or behavioral symptoms that interfere with work or usual activities, (2) documented decline from previous levels of functioning, and (3) exclusion of delirium or major psychiatric disorder; this assessment must include history from both the patient and a knowledgeable informant, objective cognitive testing, and structural brain imaging to rule out reversible causes. 1

Objective Cognitive Testing

• Neuropsychological testing is indicated when routine bedside examination cannot yield a confident diagnosis or when symptoms are reported but the examination appears normal. 1, 2

Cognitive Domain Assessment

• Assessment must document impairment in at least two of five cognitive domains; personality and behavior changes (e.g., mood fluctuations, agitation, apathy, social withdrawal) constitute one of these domains. 3

Physical Examination

• The physical examination should include an evaluation of functional abilities (e.g., activities of daily living) to help differentiate dementia from other conditions. 1

Referral to Specialist

• Patients should be referred to a dementia specialist when any of the following are present:
  
  • Onset of symptoms before age 60.
  • Atypical cognitive abnormalities such as aphasia, apraxia, or agnosia. 3
  • Sensorimotor dysfunction (e.g., cortical visual disturbances, movement or gait disorders). 3
  • Rapid progression of symptoms within weeks to months (urgent referral). 3
  • A fluctuating clinical course suggesting delirium, Lewy‑body dementia, or vascular cognitive impairment. 3
  • Discrepancy between history (significant symptoms) and a normal neurological examination. 3

Advanced Diagnostic Testing (Specialist Level)

• If diagnostic uncertainty remains after structural imaging, specialists may employ:
  
  • Fluorodeoxyglucose (FDG) PET imaging. 1
  • Cerebrospinal fluid analysis for amyloid‑β42 and tau/p‑tau biomarkers. 1
  • Amyloid PET scanning, applied according to appropriate‑use criteria. 1
• For individuals with a likely autosomal‑dominant family history of dementia, genetic testing should be considered with involvement of a genetic counselor throughout the process. 1

Critical Diagnostic Pitfalls

• Dementia must not be confused with depression (pseudodementia), which can mimic cognitive impairment. 1
• Diagnosis should not be based solely on a single cognitive domain impairment; at least two domains must be affected. 2

Evidence‑Based Cognitive Assessment for Dementia Diagnosis

Screening Tools and Their Limitations

• Brief cognitive screens such as the Mini‑Cog, Memory Impairment Screen, and the MMSE are useful for documenting severity but cannot alone establish a dementia diagnosis; a comprehensive clinical assessment is required. Strength of evidence: observational data indicating limited diagnostic specificity. 4

Comprehensive Cognitive Testing

• When initial screening suggests impairment, clinicians should use more sensitive instruments—Montreal Cognitive Assessment (MoCA), Saint Louis University Mental Status (SLUMS), or Rowland Universal Dementia Assessment Scale (RUDAS)—which demonstrate sensitivity greater than 80 % for detecting mild cognitive impairment and early dementia compared with the older MMSE. Strength of evidence: comparative study showing higher sensitivity. 4