Differential diagnosis in clinical neuropsychology: A case example of assessment without testing

Neuropsychological testing is the standard of care in the United States for assessing functional deficits related to cognitive impairment. However, there are well-known limitations of neuropsychological testing, including issues of reliability and validity, appropriate norming, predictive and ecological validity, and cultural appropriateness. The goal of this case example is to differentiate assessment from testing and to describe how assessment of brain-behavior relationships can be conducted when testing data are not available.

This case example describes a neuropsychological differential diagnosis where the individual being examined was unable to participate in any standardized testing and had no available brain imaging. By necessity, the entirety of the differential diagnosis rests on the history and behavioral observations. This case is presented as a fact-finding exercise, as it would be in a board examination to assess neuropsychological competencies.

The diagnostic value of history and behavioral observations are discussed in the context of disease base rates to rule in/rule out differential diagnoses involving the peripheral and central nervous systems. Clearly, standardized neuropsychological testing would add important data to revise and refine diagnoses and to develop treatment interventions.

Neuropsychological competency examinations usually observe clinicians in a controlled environment with comprehensive information, similar to demonstrating swimming skills in a swimming pool. However, neuropsychologists should also be able to swim in the ocean, where the setting is not well controlled, comprehensive information may not be available, and the waters are often murky, such as when assessing patients where standardized testing is not possible. (PsycInfo Database Record (c) 2026 APA, all rights reserved).