Cognitive function is thought of as a combination of multiple cognitive domains responsible for specific functions of the brain, such as attention, concentration, memory, cognitive speed, executive function, language, visual spatial skills, and praxis. The ultimate tool to assess cognitive function in an objective manner that provides a quantitative measure is neuropsychological testing. This entails a few hours of testing typically performed or supervised by a licensed neuropsychologist. A few shorter tools have been developed over the years that clinicians can use at the bedside. Some tools are more thorough than others, but they are all considered screening tools with limitations. Examples of such tools are Minicog, MMSE, SLUMS, MOCA.
All these screening tools provide a global score, however, performance on each individual test within a given examination is as important as the global score. For example, two patients might score 20/30 on a given examination, but in one patient, the deficit could be all due to poor memory, while in another patient, the deficit could be due to a combination of attention, executive, and language dysfunction. Although these two theoretical patients had identical scores, the clinical significance of their cognitive impairment would be different and the implications in terms of their diagnosis, treatment, and ability to function in their daily life are vastly different.
The purpose of these examinations is to assess current cognitive function and provide a possible prognosis with regards to progression over the years. These tests are often repeated every so often, yearly, or sometimes every few years, and the change in the score and performance might indicate either that the cognitive function has remained stable or that it has declined.
It is also important to note that even though these cognitive examinations are meant to be objective, the administration method and scoring technique can vary from clinician to clinician. Some examinations, such as MOCA, require the clinician to go through online training and obtain a certification to be allowed to administer the test, while others, such as SLUMS and MMSE, do not require such training. Therefore, two clinicians administering the same test to the same patient might end up with different scores.