Assessing Cognitive Disorders

Image: “_MG_0555” by Adrián Martínez. License: CC BY-SA 2.0

Definition of Cognitive Disorders

Cognitive disorders are a group of mental health disorders which predominantly affect learning, memory, perception and problem-solving. They result primarily from primary and secondary abnormalities of the central nervous system.

Four major kinds of cognitive disorders are:

• Delirium: It is characterized by reduced attention/awareness which develops over a short period of time and in a dramatic manner. Toxins and illnesses cause the condition. It is usually reversible.
• Dementia: Unlike delirium, dementia is a chronic and progressive loss of cognitive function, characterized by memory problems, confused thinking, and inability to concentrate. Common causes of dementia include infarction, HIV/AIDS, and Alzheimer’s disease.
• Amnesia: In this condition, a significant loss of memory occurs, but there is no loss of other cognitive functions as seen in dementia.
• Cognitive disorders not otherwise specified: In this kind, cognitive impairment may be due to a general medical condition or substance use.

Tests Performed to Assess Cognitive Function

Mini-mental Status Examination (MMSE)

Advantages

• Short screening structured test to measure cognitive impairment
• Takes approximately 5—10 minutes and covers many cognitive functions
• Easy to establish the score and know the patient’s level of cognitive function.

Disadvantages

• Not helpful for the uneducated as it includes language and mathematical testing
• For mild cognitive impairment, other tests need to be performed
• Questions are verbal; hence it is difficult to measure visuospatial and/or constructional praxis.

The test

The test consists of 11 questions with 5 areas of cognitive function: orientation, registration, attention and calculation, recall, and language can be measured.

Interpreting the Results of Tests Performed to Assess Cognitive Function

MMSE Scoring

24—30: No cognitive impairment

18—23: Mild cognitive impairment

0—17: Severe cognitive impairment

Montreal Cognitive Assessment (MoCA)

It a brief screening test designed to detect cognitive impairment in elders.

Advantages:

• Accessible online and available in several languages
• A good test for an educated person who has only a memory impairment complaint
• A 30-point test which takes about 10 minutes
• Compared to MMSE, this test is more sensitive for the detection of mild cognitive impairment
• Assesses other cognitive domains, such as memory, language, attention, visuospatial and executive functions.

Cognitive domains:

Thirty items assess these multiple cognitive domains:

• Short-term memory recall – 5 points
• Visuospatial abilities evaluated using a clock-drawing task – 3 points and a three-dimensional cube copy task – 1 point
• Executive functioning measured by an adaptation of Trail Making Test – 1 point
• Phonemic fluency – 1 point
• Verbal abstraction – 2 points
• Attention, concentration, and working memory measured using target detection – 1 point
• Serial subtraction – 3 points
• Digits forward – 1 point
• Digits backward – 1 point
• Language measured by confrontation naming of low-familiarity animals – 3 points
• Complex sentences repeated – 2 points
• Orientation to time and place evaluated – 6 points

Interpreting results:

MoCA scoring

Total possible score – 30 points

The score of 26 or above is considered normal

Mini-Cog:

It consists of 2 components:

• 3-words recall test for memory where you score 1 point for each word recalled without cues. Score 0—3.

Scoring: 1 point for each word recalled without cues. Score 0—3.

Simple Decision Tree

“Simple Decision Tree.” by Lecturio.

Clock drawing where you score form 0—2 with :

• 2 points representing normal clock where a normal clock should include all numbers from 1—12 in the correct order and clockwise direction.
• 0 point representing abnormal clock (abnormal hands or missing numbers)..

Advantages of the Mini-Cog:

• Sensitive to measure dementia status
• Short testing time compared to MMSE
• Diagnostic value not limited by the subject’s education or language.

Disadvantages

As a screening test, it does not substitute for a complete diagnostic workup.

Interpreting the Mini-Cog Score:

A mini-cog score can be obtained by adding recall and CDT scores.

• 0—2 points suggest possible impairment.
• 3—5 points suggest no impairment.