Dementia: Assessment of cognitive impairment
All patients suspected of having dementia should have a recent physical examination, including a screening neurological examination and review of medications as a part of the evaluation.
Quick cognitive screening tests
Recommended here are screening tests that are feasible and that allow the clincian to probe various brain functions, while also identifying early changes and changes over time.
This section describes a standard screening test, the Mini-Mental State Examination (MMSE), and a brief screening test called the Mini-Cog. It also lists other recommended standardized tests for dementia.
Mini-Mental State Examination
The MMSE (Folstein et al., 1975) is an 11- item test that takes five to 10 minutes to administer:
- scoring: suggested cut-off score of 24 or less out of 30 should raise concerns regarding possible dementia
- influenced by age, education
- test items most sensitive to detection of dementia: orientation to date especially year), delayed word recall, intersecting pentagons
- pros: familiar; relatively short time to administer
- cons: takes longer than other similar tests; examines limited number of cognitive domains (less emphasis on memory and executive functioning); often not sensitive to early cognitive change
The Mini-Cog (Borson et al., 2000) combines the delayed three-word recall and the clock-drawing test:
- First give the three-word registration: "I am going to say three words. I want you to repeat them back to me." Tell the patient that he or she will also be asked to recall them later.
- Then 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 below.
- Ask the patient to recall the three words.
This one-item test 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 for 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 here for detection and monitoring, including delirium
Scoring the Mini-Cog
Suggested scoring of the Mini-Cog:
- three out of three on delayed recall indicates normal; zero out of three indicates likely dementia
- for one or two out of three on word recall:
- clock-drawing test normal = no dementia
- clock-drawing test abnormal = dementia
The Mini-Cog should be considered as a first-line cognitive screen in primary care. Note that the Mini-Cog has not been evaluated as extensively as the MMSE or the Montreal Cognitive Assessment (see below).
This is a word-generation test that takes one minute to administer:
- Ask 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 less than 10 animals in one minute.
Montreal Cognitive Assessment (MoCA)
The MoCA (Nasreddine, et al., 2005) is an 11 -item test that takes 10 to 15 minutes to administer:
- scoring: total score possible is 30 (like MMSE); 26–30 = likely normal; 20–25 = possibly mild cognitive impairment or early dementia; < 20/30 = suspicious for dementia
- good follow-up test if abnormalities are found on the clock-drawing test or Mini-Cog to further evaluate cognition or in individuals 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 and 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 patients with more advanced cognitive impairment
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 in evaluating dementia. Specific situations for 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 for concomitant cerebrovascular disease because this may affect subsequent management.
Recommendations on screening for cognitive impairment in older adults (Canadian Task Force on Preventative Health, 2015)