Towards a neural network hypothesis for functional cognitive disorders: an extension of the Overfitted Brain Hypothesis.

Introduction: Whilst the empirical understanding of functional cognitive disorders (FCD) has advanced in recent years, theoretical and conceptual models have evolved more slowly. Existing frameworks for FCD are based on models of other functional neurological disorders or of metacognitive processes and are recognised to lack mechanistic precision.Methods: In this article, a novel application to FCD of Hoel's Overfitted Brain Hypothesis of the evolved function of dreaming is attempted.Results: This posits that the empirically observed sleep disturbance in FCD entails impaired dreaming which causes the brain to be overfitted and hence unable to generalise appropriately, producing mismatch between memory expectations and memory performance.Conclusions: This formulation of FCD is based on considerations derived from the study of neural networks and shares commonalities with Bayesian models of functional neurological disorders. Additionally, it has implications for future hypothesis-driven research in FCD and suggests a pragmatic basis for management strategies.

Matthew Baillie (1761-1823): From Shotts to Duntisbourne Abbots.

Matthew Baillie was born in Shotts, Lanarkshire, Scotland in 1761 and died at Duntisbourne Abbots, Gloucestershire, England in 1823. In the intervening years he established himself as one of the foremost anatomists of his day, publishing one of the earliest treatises on pathological anatomy, and then as physician, eventually ministering to the Royal household and other notable patients and earning a considerable fortune in the process. Amongst his many honours he received an Honorary Fellowship of the Royal College of Physicians of Edinburgh, where he is commemorated in the frieze in the Great Hall. This article follows the trajectory of his career, introducing material not found in previous biographies.

Attended with and head-turning sign can be clinical markers of cognitive impairment in older adults.

We read the paper by Soysal et al. (2017) with interest as we have experience of both the Attended With (AW) and the Head-Turning Sign (HTS) in a neurology-led cognitive disorders clinic.

Short Montreal Cognitive Assessment.

The diagnostic accuracy of the short Montreal Cognitive Assessment (s-MoCA), a cognitive screening instrument recently derived by item response theory and computerized adaptive testing from the original MoCA, for the diagnosis of dementia and mild cognitive impairment (MCI) was assessed in 2 patient cohorts referred to a dedicated memory clinic in order to examine the validity and reproducibility of s-MoCA. Diagnosis used standard clinical diagnostic criteria for dementia and MCI as reference standard (prevalence of cognitive impairment = 0.43 and 0.46 in each cohort, respectively). There were significant differences in s-MoCA test scores for dementia, MCI, and subjective memory impairment ( P ≤ .01), and s-MoCA effect sizes (Cohen d) were medium to large (range: 0.65-1.42) for the diagnosis of dementia and MCI. Using the cut-off for s-MoCA specified in the index study, it proved highly sensitive (>0.9) for diagnosis of dementia but with poor specificity (≤0.25), with moderate sensitivity (≥0.75) and specificity (≥0.60) for diagnosis of MCI. In conclusion, in these pragmatic diagnostic test accuracy studies, s-MoCA proved acceptable and sensitive for the diagnosis of cognitive impairment in a memory clinic setting, with a performance similar to that of the original MoCA.

MACE versus MoCA: equivalence or superiority? Pragmatic diagnostic test accuracy study.

BACKGROUND: The Mini-Addenbrooke's Cognitive Examination (MACE) is a new brief cognitive screening instrument for dementia and mild cognitive impairment (MCI). Historical data suggest that MACE may be comparable to the Montreal Cognitive Assessment (MoCA), a well-established cognitive screening instrument, in secondary care settings, but no head-to-head study has been reported hitherto. METHODS: A pragmatic diagnostic accuracy study of MACE and MoCA was undertaken in consecutive patients referred over the course of one year to a neurology-led Cognitive Function Clinic, comparing their performance for the diagnosis of dementia and MCI using various test metrics. RESULTS: In a cohort of 260 patients with dementia and MCI prevalence of 17% and 29%, respectively, both MACE and MoCA were quick and easy to use and acceptable to patients. Both tests had high sensitivity (>0.9) and large effect sizes (Cohen's d) for diagnosis of both dementia and MCI but low specificity and positive predictive values. Area under the receiver operating characteristic curve was excellent for dementia diagnosis (both >0.9) but less good for MCI (MoCA good and MACE fair). In contrast, weighted comparison suggested test equivalence for dementia diagnosis but with a slight net benefit for MACE for MCI diagnosis. CONCLUSIONS: MACE is an acceptable and accurate test for the assessment of cognitive problems, with performance comparable to MoCA. MACE appears to be a viable alternative to MoCA for testing patients with cognitive complaints in a secondary care setting.

Relapsing polychondritis complicated by cognitive dysfunction: two distinct clinical phenotypes?

Relapsing polychondritis (RPC) is a rare, immune-mediated condition affecting approximately 3.5 per million population per year. Neurological involvement in RPC is still rarer and is presumed to be the result of a vasculitic process, although this is seldom confirmed in the literature. We present two cases of RPC complicated by cognitive dysfunction with contrasting clinical trajectories. Our findings suggest that there are two clinical phenotypes of cognitive dysfunction in RPC. The first is a fulminant, multisystem presentation with sub-acute cognitive decline mimicking central nervous system vasculitis, and we provide histopathological evidence of this process occurring. The other is an insidious cognitive decline without associated constitutional or systemic symptoms.

Correlation or Limits of Agreement? Applying the Bland-Altman Approach to the Comparison of Cognitive Screening Instruments.

BACKGROUND/AIMS: Calculation of correlation coefficients is often undertaken as a way of comparing different cognitive screening instruments (CSIs). However, test scores may correlate but not agree, and high correlation may mask lack of agreement between scores. The aim of this study was to use the methodology of Bland and Altman to calculate limits of agreement between the scores of selected CSIs and contrast the findings with Pearson's product moment correlation coefficients between the test scores of the same instruments. METHODS: Datasets from three pragmatic diagnostic accuracy studies which examined the Mini-Mental State Examination (MMSE) vs. the Montreal Cognitive Assessment (MoCA), the MMSE vs. the Mini-Addenbrooke's Cognitive Examination (M-ACE), and the M-ACE vs. the MoCA were analysed to calculate correlation coefficients and limits of agreement between test scores. RESULTS: Although test scores were highly correlated (all >0.8), calculated limits of agreement were broad (all >10 points), and in one case, MMSE vs. M-ACE, was >15 points. CONCLUSION: Correlation is not agreement. Highly correlated test scores may conceal broad limits of agreement, consistent with the different emphases of different tests with respect to the cognitive domains examined. Routine incorporation of limits of agreement into diagnostic accuracy studies which compare different tests merits consideration, to enable clinicians to judge whether or not their agreement is close.

AD8 Informant Questionnaire for Cognitive Impairment: Pragmatic Diagnostic Test Accuracy Study.

The diagnostic accuracy of the AD8 informant questionnaire for cognitive impairment was assessed in patients referred to a dedicated memory clinic. This pragmatic prospective study of consecutive referrals attending with an informant who completed AD8 (n = 212) lasted 12 months. Diagnosis used standard clinical diagnostic criteria for dementia and mild cognitive impairment as reference standard (prevalence of cognitive impairment = 0.62). The AD8 proved acceptable to informants, was quick, and easy to use. Using the cutoff of ≥2/8, AD8 was highly sensitive (0.97) for diagnosis of cognitive impairment but specificity was poor (0.17). Combining AD8 with either the Mini-Mental State Examination or the Six-Item Cognitive Impairment Test showed little additional diagnostic benefit. In conclusion, AD8 is very sensitive for cognitive impairment in a memory clinic but specificity may be inadequate.

Six-item cognitive impairment test (6CIT): pragmatic diagnostic accuracy study for dementia and MCI.

BACKGROUND: The six-item cognitive impairment test (6CIT) is a brief cognitive screening instrument (CSI) recommended for use in primary care settings. There are very few studies of 6CIT performance in secondary care settings. METHODS: We undertook a pragmatic diagnostic accuracy study of 6CIT in consecutive patients referred over the course of one year to a neurology-led cognitive function clinic, and compared its performance for the diagnosis of dementia and mild cognitive impairment (MCI) to that of the simultaneously administered Mini-Mental State Examination (MMSE). RESULTS: In a cohort of 245 patients with dementia prevalence around 20%, 6CIT proved quick and easy to use and acceptable to patients. It had good sensitivity (0.88) and specificity (0.78) for dementia diagnosis; it was more sensitive than MMSE (0.59) but less specific (0.85). For MCI diagnosis, 6CIT was again more sensitive (0.66) than MMSE (0.51) but less specific (0.70 vs. 0.75). Weighted comparisons showed net benefit for 6CIT compared to MMSE for both dementia and MCI diagnosis. 6CIT effect sizes (Cohen's d) were large for dementia diagnosis and moderate for MCI diagnosis. CONCLUSIONS: 6CIT is an acceptable and accurate test for the assessment of cognitive problems, its performance being more sensitive than the MMSE. 6CIT use should be considered as a viable alternative to MMSE in the secondary care setting.

Phantasia, aphantasia, and hyperphantasia: Empirical data and conceptual considerations.

Within the past decade, the term "phantasia" has been increasingly used to describe the human capacity, faculty, or power of visual mental imagery, with extremes of imagery vividness characterised as "aphantasia" and "hyperphantasia". A substantial volume of empirical research addressing these constructs has now been published, including attempts to find inductive correlates of behaviourally defined aphantasia, for example using research questionnaires and functional magnetic resonance imaging. Mental imagery has long been noted as a source of conceptual confusions but no specific conceptual analysis of the new formulation of phantasia, aphantasia, and hyperphantasia has been undertaken hitherto. We offer some conceptual considerations on phantasia, noting the ongoing confusion of perceptual with mental images, and the ubiquitous use of unvalidated subjective assessment instruments such as the Vividness of Visual Imagery Questionnaire (VVIQ) in diagnosis and assessment, development of which was predicated on these conceptual confusions. We offer some suggestions for a conceptual framework for future empirical studies in this field, circumventing these conceptual confusions.

Charles Dickens (1812-1870) and epilepsy.

To coincide with the bicentenary of the birth of Charles Dickens (1812-1870), accounts of epilepsy found in his novels and journalism have been collated and analyzed. From these, it may be inferred that Dickens was clearly aware of the difference between epilepsy and syncope and recognized different types of epilepsy and that seizures could be fatal. Speculations that Dickens himself suffered from epilepsy are not corroborated. Dickens's novelistic construction of epilepsy as a marker of criminality, as in the characters of Monks in Oliver Twist and Bradley Headstone in Our Mutual Friend, and perhaps of mental abnormality, was in keeping with conventional contemporary views of epilepsy, but his journalistic descriptions of individuals with epilepsy confined in the workhouse system indicate an awareness of the inadequacy of their care.

Screening utility of the Montreal Cognitive Assessment (MoCA): in place of--or as well as--the MMSE?

BACKGROUND: This aim of this study was to assess the clinical utility of the Montreal Cognitive Assessment (MoCA) as a screening instrument for cognitive impairment in patients referred to a memory clinic, alone and in combination with the Mini-Mental State Examination (MMSE). METHODS: This was a pragmatic prospective study of consecutive referrals attending a memory clinic (n = 150) over an 18-month period. Patients were diagnosed using standard clinical diagnostic criteria for dementia (DSM-IV) and mild cognitive impairment (MCI; cognitive impairment prevalence = 43%) independent of MoCA test scores. RESULTS: MoCA proved acceptable to patients and was quick and easy to use. Using the cut-offs for MoCA and MMSE specified in the index paper (≥26/30), MoCA was more sensitive than MMSE (0.97 vs 0.65) but less specific (0.60 vs 0.89), with better diagnostic accuracy (area under Receiver Operating Characteristic curve 0.91 vs 0.83). Downward adjustment of the MoCA cut-off to ≥20/30 maximized test accuracy and improved specificity (0.95) for some loss of sensitivity (0.63). Combining MoCA with the MMSE - either in series or in parallel - did not improve diagnostic utility above that with either test alone. CONCLUSIONS: In a memory clinic population, MoCA proved sensitive for the diagnosis of cognitive impairment. Use of a cut-off lower than that specified in the index study may be required to improve overall test accuracy and specificity for some loss of sensitivity in populations with a high prior probability of cognitive impairment. Combining the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) with the MMSE did not improve diagnostic utility.