Evaluating Cognitive Impairment and Dementia
Screening includes office-based assessments of cognitive function, as well as laboratory testing and neuroimaging. All patients suspected of having dementia should have a physical examination, including a screening neurological examination and review of medications, as a part of the evaluation.
Quick Cognitive Screening Tests
Mini-Mental State Examination
The Mini-Mental State Examination (MMSE) is an 11-item test that takes five to 10 minutes to administer (Folstein et al., 1975).
- Scoring: suggested cut-off of 24 or less out of 30 should raise concerns about possible dementia.
- Performance affected by age and education
- Test items that are most sensitive to detection: orientation to date (especially year), delayed word recall and intersecting pentagons
- Pros: familiar and takes a relatively short time to administer
- Cons: takes longer than other similar tests; tests a limited number of cognitive domains (relatively less emphasis on memory and executive functioning); often not sensitive to early cognitive change
The Mini-Cog is a first-line cognitive screen for primary care, although it has not been evaluated as extensively as the MMSE or the Montreal Cognitive Assessment. The Mini-Cog combines the delayed three-word recall test and the clock-drawing test (Borson et al., 2000).
Delayed three-word recall test
- Tell the patient: “I am going to say three words. I want you to repeat them back to me.” Explain that you will later ask the patient to recall the words.
- Use the clock-drawing test (see below) as a distracter for the three-word recall. The scoring of the clock is similar to the Mini-Cog scoring described on page 229.
- Ask the patient to recall the three words.
This test involves one item, and takes one to two minutes to administer.
- Test: “Please draw a clock and make the time show 10 minutes past 11:00.”
- Scoring: normal (perfect or near perfect) or abnormal by inspection; any abnormal clock should raise suspicion of dementia and prompt further evaluation.
- Pros: not influenced by age or education; easy, very quick and acceptable to most patients; some measure of visuospatial and executive function
- Cons: does not test memory or language abilities
- Recommended for detection and monitoring, including delirium
Scoring the Mini-Cog
- 3 out of 3 on delayed recall indicates normal; 0 out of 3 indicates likely dementia.
- 1 or 2 out of 3 on word recall: normal clock-drawing test = no dementia; abnormal clock-drawing test = dementia
- This word-generation test asks patients to name as many four-legged animals as they can in one minute.
- Tell patients that the test is not a race and that they will have one minute to complete the test from the point that they say the first word.
- People with dementia are 25 times more likely to name fewer than 10 animals in one minute.
Montreal Cognitive Assessment (MoCA)
The MoCA is an 11-item test that takes 10 to 15 minutes to administer (Nasreddine et al., 2005).
- Scoring: total score possible is 30 (like MMSE); 26–30 = likely normal; 20–25 = possibly mild cognitive impairment or early dementia; < 20 = suspicious for dementia
- Good follow-up test if abnormalities are found on the clock-drawing test or Mini-Cog to further evaluate cognition and for people with cognitive complaints and normal scores on brief screening exams
- Test packages and instructions available online in multiple languages; adjustment for education included in the testing
- Pros: free, easy to access, available in more than 20 languages; sensitive for dementia and mild cognitive impairment; tests executive function in detail and features a more rigorous memory section; trail-making section for evaluating driving safety; very useful in primary care
- Cons: more time-consuming than other tests; may be frustrating for people with more advanced cognitive impairment; may be affected by sensory deficits such as visual or hearing impairment; may be affected by literacy and education level, which can limit the test’s utility in some populations.
Laboratory Screening Tests
Routine laboratory tests should include:
- complete blood count
- serum electrolytes
- serum calcium
- TSH and glucose.
Further investigations that may be useful in evaluating for possible dementia include measures of renal function and liver enzymes, and an ECG.
Indications for Neuroimaging
Neuroimaging is not routinely recommended for evaluating dementia. Specific situations in which neuroimaging (CT scan of the head) should be considered include:
- age at dementia onset < 60
- focal neurological signs
- rapid progression of dementia
- recent head trauma
- use of anticoagulants
- unusual symptoms or gait disturbance.
Neuroimaging is also recommended to evaluate concomitant cerebrovascular disease because it may affect management.
- The Primary Care Practitioner Role
- Screening & Assessment
- Resources & References