REFERENCE · DIAGNOSTIC TECHNIQUE

Internal Inconsistency and Clinical Assessment

Clinician-focused educational reference; use within professional competence, consent and an individual assessment plan.

Purpose and Suitability
Anatomy and Physiology
Preparation and Safety
Performing the Assessment
Interpreting Findings
Explaining the Result
Evidence and Limitations
Media and Accessibility
Research and Sources

Purpose and Suitability

Establish whether the cognitive complaint has a positive functional pattern, assess alternatives and decide what remains uncertain. Cognitive neurology, general practice, neuropsychology and the rehabilitation team contribute different observations.

Internal inconsistency: A clinically meaningful difference in access to the same cognitive ability across contexts, after accounting for demands and other explanations.

The clinician identifies a specific mismatch within a cognitive ability, such as better use during ordinary interaction than during focused testing. This is the central positive concept. Ordinary fluctuation, distress or a normal screening score alone is insufficient. [1]

A request to measure support needs can proceed alongside diagnostic assessment. Use the separate OT measurement guide; a diagnosis alone does not quantify disability.

Anatomy and Physiology

Memory, attention, language and executive functions work together. The comparison must specify the process being assessed: remembering an event, following an instruction and finding a word impose different demands. See the cognitive-process explanation.

Encoding: Taking information in so it can be remembered. Retrieval: Bringing previously learned information back to mind.

The proposed clinical framework describes a functional pattern; it does not establish a single biological mechanism or prove that every inaccessible memory remains intact. [1]

Preparation and Safety

Explain the assessment in advance and invite written examples or an existing calendar if helpful. Agree breaks and communication access. Document hearing, vision, language, pain, fatigue and medication context before interpreting differences.

Teaching safeguards: do not remove essential aids, create overload or exhaust the person to reveal a discrepancy. Sudden confusion, altered consciousness or new focal neurological symptoms needs urgent assessment; a progressive change also needs review. Obtain permission for supporter information, and explain confidentiality.

Performing the Assessment

Define the cognitive complaint, onset, course, variability and functional consequences. Ask for specific recent examples rather than accepting or rejecting a global label such as “memory loss.”
Observe how the patient follows the conversation, recalls autobiographical and appointment details, uses aids, corrects errors and manages multistep information during the encounter.
With consent, obtain collateral examples of both difficulty and preserved ability. Interpret differences between accounts respectfully and in context.
Use validated cognitive screening or neuropsychological assessment when it will answer a clinical question. Follow test-security, language, education and performance-validity standards.
Look for internal inconsistency across history, observed behaviour, day-to-day function and test performance. The contrast should be clinically meaningful and not explained more plausibly by task demands or fluctuating health.
Evaluate sleep, pain, fatigue, medication and substance effects, mood, anxiety, ADHD, epilepsy, head injury, neurodevelopmental factors, neurodegenerative disease and other relevant causes or comorbidities.
Explain the positive formulation without saying “nothing is wrong.” State the degree of certainty and arrange follow-up if progression or a new pattern emerges.

This original sequence is an educational outline, not a validated seven-item score. [1][2]

Conversation versus formal performance

Detailed, coherent accounts can be compared with the particular impairment claimed during testing. The comparison must concern the same ability and allow for anxiety, pain, fatigue, language and sensory barriers. It is supportive clinical reasoning, not a test of honesty. [1][2]

Everyday function and collateral history

With consent, the clinician compares the person’s account, a supporter’s observations and actual daily tasks. A specific inconsistency may be useful, but compensatory strategies can preserve daily function despite neurological disease. Disagreement alone is not a positive sign. [1][2]

Write down the task, the ability being compared, assistance and competing explanations. A rehearsed account and a new learning task do not test identical demands.

Interpreting Findings

Supportive: Name a specific same-domain inconsistency and why it remains informative after contextual differences are considered.

Not demonstrated: Normal screening or an uneventful consultation supplies no positive FCD finding by itself.

Indeterminate or mixed: State what limits interpretation and what evidence would help. FCD and another cognitive disorder can coexist. The proposed criteria include clinically significant distress or impairment and symptoms not better explained by another condition. [1]

Longitudinal assessment and investigations

Follow-up and selected laboratory, imaging or other tests address plausible competing or coexisting causes. Stability may contribute to the formulation but does not prove FCD. A positive diagnosis should explain current findings and what would prompt review. [1]

Record a review interval, responsible clinician and specific changes that should prompt earlier review. Everyday assessment findings should be reported even when the cause remains uncertain.

Explaining the Result

Authored example, not a patient quotation:

“I will explain the particular pattern that supports this diagnosis, and what we still need to check. That pattern does not tell us how much help you need through a whole day. We will assess that separately and write down a plan you can refer to.”

Offer a short written explanation. Ask the person to explain the plan in their own words as a check of the explanation, not an unannounced memory test.

Evidence and Limitations

Ball and colleagues proposed a clinical framework; it is not an accuracy-validated bedside manoeuvre. McWhirter and colleagues studied a small clinical cohort and proposed a risk model. Neither source makes conversational fluency or a normal score sufficient for diagnosis. [1][2]

The models guide separates research classifiers from routine clinical reasoning. No diagnostic finding should be converted into a percentage of disability.

Media and Accessibility

Use a fictional case with an actor or an annotated diagram showing four information sources:

The person’s description of the problem.
Examples of everyday difficulty and preserved ability.
Abilities observed during the appointment.
Results of appropriate validated assessment and medical evaluation.

Show how the clinician looks for a meaningful pattern across all four, rather than setting up a “gotcha” memory test. Do not display copyrighted or secured test items, scoring keys or a real patient’s identifiable daily-life details. Make clear that one inconsistency is a clue, not a diagnosis.

Research and Sources

The original clinical outline and media brief are preserved. Practical documentation, consent and accessibility suggestions are editorial safeguards. The proposed criteria and positive-diagnosis framework remain subject to clinical judgment and differential assessment.

Citation	Full citation
[1]	Ball HA, McWhirter L, Ballard C, et al. Functional cognitive disorder: dementia’s blind spot. Brain : a journal of neurology. 2020;143(10):2895-2903. DOI. PMID: 32791521. FND-CIT-0071.
[2]	McWhirter L, Ritchie C, Stone J, Carson A. Identifying functional cognitive disorder: a proposed diagnostic risk model. CNS Spectrums. 2022;27(6):754–763. FND-CIT-0026. https://doi.org/10.1017/S1092852921000845

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