Functional cognitive disorder (cogniform disorder)

Definition (McWhirter et al, 2020)

1) One or more symptoms of impaired cognitive function

2) Clinical findings show evidence of internal inconsistency: with observed or measured function, or between different situations

3) Symptoms or impairment are not better explained by another medical disorder, although might be comorbid with another medical disorder

4) Symptoms or impairment cause clinically substantial distress or impairment in social, occupational, or other important areas of function, or warrant medical evaluation

Proposed overlapping subtypes (Stone et al, 2015)

1) Excessive attentional focus on normal cognitive symptoms

2) Health anxiety about dementia with perceived cognitive deficit

3) Isolated functional cognitive symptoms with or without impairment on cognitive tests

4) Cognitive symptoms as part of anxiety / depression

5) Cognitive symptoms in other functional disorders (other FND, chronic fatigue, fibromyalgia)

6) Dissociative cognitive state (dissociative amnesia, fugue, Ganser syndrome)

Diagnosis

History Clinical features more common in functional cognitive disorders vs features more common in degenerative brain disease (McWhirter et al, 2020; Stone et al, 2015; Griem et al, 2016)

- patient typically attends the appointment alone, demonstrating confidence in ability to navigate the medical system (as well as confidence from others in their abilities)

- patient is more aware of their problem than others, as opposed to degenerative brain disease in which others are typically more aware of the problem than the patient

- patient answers questions independently, as opposed to degenerative brain disease in which patients typically turn to the accompanying adult for support in answering questions (e.g. head turn sign)

- patient gives detailed description of complaints, frequently offering elaboration and detail, have detailed account of personal history, drugs, and previous interactions with doctors. They may bring written list (la maladie du petit papier - Burnum 1985). The thoroughness and detail is often not compatible with presenting complaints of cognitive dysfunction. Patients with degenerative diseases are unlikely to give spontaneous elaboration and can typically only answer single-component questions

- patient may complain of loss of recent and remote autobiographical memories (or complaints of memory gaps for specific periods and events), as opposed to typical preservation of remote autobiographical memories and following Ribot's law.

- patient's complaints of memory symptoms may be within most people's normal experience

- approximate answers (i.e. answers that indicate the correct answer is known at some level)

- unstable longitudinal course with marked variability

Cognitive testing

- Failed validity or effort measures

- Scores lower than chance (indicating that the correct answer is known at some level)

In general, patients with FND perform worse on neuropsychological tests of information processing compared to patients with somatic symptom disorder (de Vroege et al, 2020).

References

Burnum, JF. La Maladie du Petit Papier. Is Writing a List of Symptoms a Sign of an Emotional Disorder? New England Journal of Medicine. 1985 Sep 12;313(11):690-1. https://pubmed.ncbi.nlm.nih.gov/4022061/

de Vroege, L., Koppenol, I., Kop, W. J., Riem, M. M. E. & van der Feltz-Cornelis, C. M. Neurocognitive functioning in patients with conversion disorder/functional neurological disorder: Neurocognitive function in conversion disorder/FND. J. Neuropsychol. (2020) doi:10.1111/jnp.12206https://pubmed.ncbi.nlm.nih.gov/32223071/

Griem, J., Stone, J., Carson, A. & Kopelman, M. D. Psychologic/functional forms of memory disorder. in Handbook of Clinical Neurology vol. 139 407–417 (Elsevier, 2016). https://pubmed.ncbi.nlm.nih.gov/27719860/

McWhirter, L., Ritchie, C., Stone, J. & Carson, A. Functional cognitive disorders: a systematic review. Lancet Psychiatry 7, 191–207 (2020). https://pubmed.ncbi.nlm.nih.gov/31732482/

Stone, J. et al. Functional (Psychogenic) Cognitive Disorders: A Perspective from the Neurology Clinic. J. Alzheimers Dis. 48, S5–S17 (2015). https://pubmed.ncbi.nlm.nih.gov/26445274/