14 Differentiating functional cognitive disorder from early neurodegeneration: a clinic-based study
Authors: Ball Harriet A , Swirski Marta , Newson Margaret , Coulthard Elizabeth , Pennington Catherine 
Published: July 2020

Objectives/Aims

Functional Cognitive Disorder (FCD) describes distressing or disabling cognitive symptoms that can be positively identified as internally inconsistent with recognised brain or systemic disease processes. FCD is common amongst attendees to cognitive or memory clinics. We aimed to improve the clinical characterisation of such patients, and identify means to differentiate them from patients with early neurodegeneration.

Methods

We identified two samples of patients recruited from a specialist cognitive clinic, classified on the basis of consensus expert clinical opinion following relevant investigations: FCD, (n=21), and neurodegenerative Mild Cognitive Impairment ‘MCI’, (n=17). We also recruited healthy control participants (n=25). All participants completed a cognitive battery: Montreal Cognitive Assessment (MoCA), Hopkins Verbal Learning Test-Revised (HVLT-R), Trail Making Test part B (TMT-B); and the Minnesota Multiphasic Personality Inventory (MMPI-2RF). Analyses included regression models controlling for age and gender. Analysis of the personality data focused on specific hypotheses generated from previous work on functional disorders.

Results

As expected, the FCD participants were younger than the MCI participants (mean age 58 vs 72), and were more likely to be occupationally active (35% vs 6%).

As described previously in this sample*, subjective cognitive symptoms were equally elevated in FCD and MCI compared to controls. Both the FCD and MCI groups were impaired in comparison to controls on MoCA, TMT-B and the initial recall component of HVLT-R. However, FCD participants demonstrated a dip in scores from free recall to recognition on HVLT-R, which was not seen in MCI (p<0.05). FCD and MCI groups scored equally high relative to controls on anxiety and depression, and on four personality indices: emotional or internalising dysfunction, somatic complaints (cognitive and non-cognitive analysed separately), and negative emotional experiences. There were no group differences in ‘introversion/low positive emotionality’.

Conclusions

Cognitive symptoms, basic bedside cognitive testing, personality analysis, and mood symptoms are all similar across both early neurodegenerative and FCD groups, making them hard to disentangle clinically. We hope that by highlighting certain testing modalities that can illustrate internal inconsistency (such as delayed recall spared relative to recognition, as opposed to consistently poor delayed recall and recognition that is more typical of Alzheimer’s neurodegeneration), we can improve diagnosis and thereby management strategies. It is unclear why both mood and non-cognitive somatic symptoms are elevated in both FCD and MCI; this could reflect an epiphenomenon of distress surrounding the cognitive symptoms, despite diverse origins of the cognitive symptoms.

Reference

Pennington C, Ball HA, Swirski M.Functional cognitive disorder: diagnostic challenges and future directions.Diagnostics2019;9: 131.