Perspectives on the diagnosis and management of functional cognitive disorder: An international Delphi study.

BACKGROUND: Current proposed criteria for functional cognitive disorder (FCD) have not been externally validated. We sought to analyse the current perspectives of cognitive specialists in the diagnosis and management of FCD in comparison with neurodegenerative conditions. METHODS: International experts in cognitive disorders were invited to assess seven illustrative clinical vignettes containing history and bedside characteristics alone. Participants assigned a probable diagnosis and selected the appropriate investigation and treatment. Qualitative, quantitative and inter-rater agreement analyses were undertaken. RESULTS: Eighteen diagnostic terminologies were assigned by 45 cognitive experts from 12 countries with a median of 13 years of experience, across the seven scenarios. Accurate discrimination between FCD and neurodegeneration was observed, independently of background and years of experience: 100% of the neurodegenerative vignettes were correctly classified and 75%-88% of the FCD diagnoses were attributed to non-neurodegenerative causes. There was <50% agreement in the terminology used for FCD, in comparison with 87%-92% agreement for neurodegenerative syndromes. Blood tests and neuropsychological evaluation were the leading diagnostic modalities for FCD. Diagnostic communication, psychotherapy and psychiatry referral were the main suggested management strategies in FCD. CONCLUSIONS: Our study demonstrates the feasibility of distinguishing between FCD and neurodegeneration based on relevant patient characteristics and history details. These characteristics need further validation and operationalisation. Heterogeneous labelling and framing pose clinical and research challenges reflecting a lack of agreement in the field. Careful consideration of FCD diagnosis is advised, particularly in the presence of comorbidities. This study informs future research on diagnostic tools and evidence-based interventions.

Development of a smartphone screening test for preclinical Alzheimer's disease and validation across the dementia continuum.

BACKGROUND: Dementia prevalence is predicted to triple to 152 million globally by 2050. Alzheimer's disease (AD) constitutes 70% of cases. There is an urgent need to identify individuals with preclinical AD, a 10-20-year period of progressive brain pathology without noticeable cognitive symptoms, for targeted risk reduction. Current tests of AD pathology are either too invasive, specialised or expensive for population-level assessments. Cognitive tests are normal in preclinical AD. Emerging evidence demonstrates that movement analysis is sensitive to AD across the disease continuum, including preclinical AD. Our new smartphone test, TapTalk, combines analysis of hand and speech-like movements to detect AD risk. This study aims to [1] determine which combinations of hand-speech movement data most accurately predict preclinical AD [2], determine usability, reliability, and validity of TapTalk in cognitively asymptomatic older adults and [3], prospectively validate TapTalk in older adults who have cognitive symptoms against cognitive tests and clinical diagnoses of Mild Cognitive Impairment and AD dementia. METHODS: Aim 1 will be addressed in a cross-sectional study of at least 500 cognitively asymptomatic older adults who will complete computerised tests comprising measures of hand motor control (finger tapping) and oro-motor control (syllabic diadochokinesis). So far, 1382 adults, mean (SD) age 66.20 (7.65) years, range 50-92 (72.07% female) have been recruited. Motor measures will be compared to a blood-based AD biomarker, phosphorylated tau 181 to develop an algorithm that classifies preclinical AD risk. Aim 2 comprises three sub-studies in cognitively asymptomatic adults: (i) a cross-sectional study of 30-40 adults to determine the validity of data collection from different types of smartphones, (ii) a prospective cohort study of 50-100 adults ≥ 50 years old to determine usability and test-retest reliability, and (iii) a prospective cohort study of ~1,000 adults ≥ 50 years old to validate against cognitive measures. Aim 3 will be addressed in a cross-sectional study of ~200 participants with cognitive symptoms to validate TapTalk against Montreal Cognitive Assessment and interdisciplinary consensus diagnosis. DISCUSSION: This study will establish the precision of TapTalk to identify preclinical AD and estimate risk of cognitive decline. If accurate, this innovative smartphone app will enable low-cost, accessible screening of individuals for AD risk. This will have wide applications in public health initiatives and clinical trials. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT06114914, 29 October 2023. Retrospectively registered.

The Parkinson's Puzzle Box.

INTRODUCTION: Women and those with younger onset Parkinson's Disease (YOPD) are typically diagnosed later and face unique situations and challenges. This essay aims to raise awareness of the difficulties in diagnosing YOPD and the need for a personalised approach to care for women with YOPD. METHODS: Two professional women with YOPD (academic physiotherapist and practicing dentist) and a female neurologist (clinician academic) came together to write a narrative essay on their personal experience and perspectives in relation to women and YOPD. RESULTS: The essay outlines how the experience of diagnosis is likened to a complex puzzle box with many interlocking components that are hidden and difficult to solve. The concerns of the women about their identity, work, family and the future, with most supports targeting those that are older and retired are outlined. CONCLUSION: It is concluded that YOPD is a complex puzzle to solve, but can be done by understanding all the intricate interlocking components of the puzzle and combined with greater awareness could lead to earlier diagnosis and the delivery of successful person-centred care. PATIENT OR PUBLIC CONTRIBUTION: People with lived experience were involved in the essay conception and writing.

Estimating presymptomatic episodic memory impairment using simple hand movement tests: A cross-sectional study of a large sample of older adults.

INTRODUCTION: Finding low-cost methods to detect early-stage Alzheimer's disease (AD) is a research priority for neuroprotective drug development. Presymptomatic Alzheimer's is associated with gait impairment but hand motor tests, which are more accessible, have hardly been investigated. This study evaluated how home-based Tasmanian (TAS) Test keyboard tapping tests predict episodic memory performance. METHODS: 1169 community participants (65.8 ± 7.4 years old; 73% female) without cognitive symptoms completed online single-key and alternate-key tapping tests and episodic memory, working memory, and executive function cognitive tests. RESULTS: All single-key (R2 adj  = 8.8%, ΔAIC = 5.2) and alternate-key (R2 adj  = 9.1%, ΔAIC = 8.8) motor features predicted episodic memory performance relative to demographic and mood confounders only (R2 adj  = 8.1%). No tapping features improved estimation of working memory. DISCUSSION: Brief self-administered online hand movement tests predict asymptomatic episodic memory impairment. This provides a potential low-cost home-based method for stratification of enriched cohorts. HIGHLIGHTS: We devised two brief online keyboard tapping tests to assess hand motor function. 1169 cognitively asymptomatic adults completed motor- and cognitive tests online. Impaired hand motor function predicted reduced episodic memory performance. This brief self-administered test may aid stratification of community cohorts.

Functional neurological disorder is a feminist issue.

Functional neurological disorder (FND) is a common and disabling disorder, often misunderstood by clinicians. Although viewed sceptically by some, FND is a diagnosis that can be made accurately, based on positive clinical signs, with clinical features that have remained stable for over 100 years. Despite some progress in the last decade, people with FND continue to suffer subtle and overt forms of discrimination by clinicians, researchers and the public. There is abundant evidence that disorders perceived as primarily affecting women are neglected in healthcare and medical research, and the course of FND mirrors this neglect. We outline the reasons why FND is a feminist issue, incorporating historical and contemporary clinical, research and social perspectives. We call for parity for FND in medical education, research and clinical service development so that people affected by FND can receive the care they need.

Isolated rapid eye movement sleep behaviour disorder (iRBD) in the Island Study Linking Ageing and Neurodegenerative Disease (ISLAND) Sleep Study: protocol and baseline characteristics.

Isolated rapid eye movement (REM) sleep behaviour disorder (iRBD) is a sleep disorder that is characterised by dream enactment episodes during REM sleep. It is the strongest known predictor of α-synuclein-related neurodegenerative disease (αNDD), such that >80% of people with iRBD will eventually develop Parkinson's disease, dementia with Lewy bodies, or multiple system atrophy in later life. More research is needed to understand the trajectory of phenoconversion to each αNDD. Only five 'gold standard' prevalence studies of iRBD in older adults have been undertaken previously, with estimates ranging from 0.74% to 2.01%. The diagnostic recommendations for video-polysomnography (vPSG) to confirm iRBD makes prevalence studies challenging, as vPSG is often unavailable to large cohorts. In Australia, there have been no iRBD prevalence studies, and little is known about the cognitive and motor profiles of Australian people with iRBD. The Island Study Linking Ageing and Neurodegenerative Disease (ISLAND) Sleep Study will investigate the prevalence of iRBD in Tasmania, an island state of Australia, using validated questionnaires and home-based vPSG. It will also explore several cognitive, motor, olfactory, autonomic, visual, tactile, and sleep profiles in people with iRBD to better understand which characteristics influence the progression of iRBD to αNDD. This paper details the ISLAND Sleep Study protocol and presents preliminary baseline results.

A new one-stop interdisciplinary cognitive clinic model tackles rural health inequality and halves the time to diagnosis: Benchmarked against a national dementia registry.

OBJECTIVES: Unequal access to cognitive assessments is a major barrier to timely diagnosis, especially for those living in rural or remote areas. 'One-stop' cognitive clinic models are a proposed solution, but few such clinics exist. We evaluate the implementation of a new one-stop State-wide clinic model in Tasmania, Australia, where 27% of people live in rural/remote areas. METHODS: A novel single-visit protocol has been developed, comprising interdisciplinary medical and cognitive assessments, research participation, consensus diagnosis and management plan. A cross-sectional evaluation was undertaken using the RE-AIM (reach, effectiveness, adoption, implementation, maintenance) framework and results benchmarked against the national Australian Dementia Network Registry. RESULTS: Over the first 52 consecutive weekly clinics: Reach: 130 adults were assessed (mean age [SD] 70.12 years [10.31]; 59.2% female) with 40 (36.8%) from rural/remote areas. EFFECTIVENESS: 98.5% (128/130) received a same-day diagnosis: 30.1% (n = 40) Subjective Cognitive Decline, 35.4% (46) Mild Cognitive Impairment, 33.1% (43) dementia and one case inconclusive. Adoption: 22.9% (156) of General Practitioners referred patients. IMPLEMENTATION: Nearly all 'ideal' diagnostic clinical practices were met and >90% of surveyed patients reported 'good/very good' clinic experience. The wait from referral to diagnosis was 2 months shorter than other national Registry clinics (78 vs. 133 days). CONCLUSIONS: This 'one-stop' model provides an interdisciplinary consensus cognitive diagnosis quickly and is well accepted; this may reduce health inequities especially for people living in rural/remote areas. This cognitive clinic model may be of relevance to other centres worldwide and also provides a rich data source for research studies.

An online, public health framework supporting behaviour change to reduce dementia risk: interim results from the ISLAND study linking ageing and neurodegenerative disease.

BACKGROUND: Unmanaged cardiometabolic health, low physical and cognitive activity, poor diet, obesity, smoking and excessive alcohol consumption are modifiable health risk factors for dementia and public health approaches to dementia prevention have been called for. The Island Study Linking Ageing and Neurodegenerative Disease (ISLAND) is a dementia prevention public health study examining whether improving knowledge about modifiable dementia risk factors supports behaviour changes that reduce future dementia risk. METHODS: Residents of Tasmania, Australia, aged 50 + years who joined the 10-year ISLAND study were asked to complete annual online surveys about their knowledge, motivations and behaviours related to modifiable dementia risk. ISLAND included two knowledge-based interventions: a personalised Dementia Risk Profile (DRP) report based on survey responses, and the option to do a 4-week Preventing Dementia Massive Open Online Course (PDMOOC). Longitudinal regression models assessed changes in the number and type of risk factors, with effects moderated by exposures to the DRP report and engagement with the PDMOOC. Knowledge and motivational factors related to dementia risk were examined as mediators of risk behaviour change. RESULTS: Data collected between October 2019 and October 2022 (n = 3038, av. 63.7 years, 71.6% female) showed the mean number of modifiable dementia risk factors per participant (range 0 to 9) reduced from 2.17 (SD 1.24) to 1.66 (SD 1.11). This change was associated with the number of exposures to the DRP report (p = .042) and was stronger for PDMOOC participants (p = .001). The interaction between DRP and PDMOOC exposures yielded a significant improvement in risk scores (p = .004). The effect of PDMOOC engagement on behaviour change was partly mediated by increased knowledge (12%, p = .013). Self-efficacy enhanced the effect of knowledge on behaviour change, while perceived susceptibility to dementia mitigated this relationship. CONCLUSIONS: The ISLAND framework and interventions, a personalised DRP report and the four-week PDMOOC, work independently and synergistically to increase dementia risk knowledge and stimulate health behaviour change for dementia risk reduction. ISLAND offers a feasible and scalable public health approach for redressing the rising prevalence of dementia.

The TAS Test project: a prospective longitudinal validation of new online motor-cognitive tests to detect preclinical Alzheimer's disease and estimate 5-year risks of cognitive decline and dementia.

BACKGROUND: The worldwide prevalence of dementia is rapidly rising. Alzheimer's disease (AD), accounts for 70% of cases and has a 10-20-year preclinical period, when brain pathology covertly progresses before cognitive symptoms appear. The 2020 Lancet Commission estimates that 40% of dementia cases could be prevented by modifying lifestyle/medical risk factors. To optimise dementia prevention effectiveness, there is urgent need to identify individuals with preclinical AD for targeted risk reduction. Current preclinical AD tests are too invasive, specialist or costly for population-level assessments. We have developed a new online test, TAS Test, that assesses a range of motor-cognitive functions and has capacity to be delivered at significant scale. TAS Test combines two innovations: using hand movement analysis to detect preclinical AD, and computer-human interface technologies to enable robust 'self-testing' data collection. The aims are to validate TAS Test to [1] identify preclinical AD, and [2] predict risk of cognitive decline and AD dementia. METHODS: Aim 1 will be addressed through a cross-sectional study of 500 cognitively healthy older adults, who will complete TAS Test items comprising measures of motor control, processing speed, attention, visuospatial ability, memory and language. TAS Test measures will be compared to a blood-based AD biomarker, phosphorylated tau 181 (p-tau181). Aim 2 will be addressed through a 5-year prospective cohort study of 10,000 older adults. Participants will complete TAS Test annually and subtests of the Cambridge Neuropsychological Test Battery (CANTAB) biennially. 300 participants will undergo in-person clinical assessments. We will use machine learning of motor-cognitive performance on TAS Test to develop an algorithm that classifies preclinical AD risk (p-tau181-defined) and determine the precision to prospectively estimate 5-year risks of cognitive decline and AD. DISCUSSION: This study will establish the precision of TAS Test to identify preclinical AD and estimate risk of cognitive decline and AD. If accurate, TAS Test will provide a low-cost, accessible enrichment strategy to pre-screen individuals for their likelihood of AD pathology prior to more expensive tests such as blood or imaging biomarkers. This would have wide applications in public health initiatives and clinical trials. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT05194787 , 18 January 2022. Retrospectively registered.

Applications of artificial intelligence to aid early detection of dementia: A scoping review on current capabilities and future directions.

BACKGROUND & OBJECTIVE: With populations aging, the number of people with dementia worldwide is expected to triple to 152 million by 2050. Seventy percent of cases are due to Alzheimer's disease (AD) pathology and there is a 10-20 year 'pre-clinical' period before significant cognitive decline occurs. We urgently need, cost effective, objective biomarkers to detect AD, and other dementias, at an early stage. Risk factor modification could prevent 40% of cases and drug trials would have greater chances of success if participants are recruited at an earlier stage. Currently, detection of dementia is largely by pen and paper cognitive tests but these are time consuming and insensitive to the pre-clinical phase. Specialist brain scans and body fluid biomarkers can detect the earliest stages of dementia but are too invasive or expensive for widespread use. With the advancement of technology, Artificial Intelligence (AI) shows promising results in assisting with detection of early-stage dementia. This scoping review aims to summarise the current capabilities of AI-aided digital biomarkers to aid in early detection of dementia, and also discusses potential future research directions. METHODS & MATERIALS: In this scoping review, we used PubMed and IEEE Xplore to identify relevant papers. The resulting records were further filtered to retrieve articles published within five years and written in English. Duplicates were removed, titles and abstracts were screened and full texts were reviewed. RESULTS: After an initial yield of 1,463 records, 1,444 records were screened after removal of duplication. A further 771 records were excluded after screening titles and abstracts, and 496 were excluded after full text review. The final yield was 177 studies. Records were grouped into different artificial intelligence based tests: (a) computerized cognitive tests (b) movement tests (c) speech, conversion, and language tests and (d) computer-assisted interpretation of brain scans. CONCLUSIONS: In general, AI techniques enhance the performance of dementia screening tests because more features can be retrieved from a single test, there are less errors due to subjective judgements and AI shifts the automation of dementia screening to a higher level. Compared with traditional cognitive tests, AI-based computerized cognitive tests improve the discrimination sensitivity by around 4% and specificity by around 3%. In terms of speech, conversation and language tests, combining both acoustic features and linguistic features achieve the best result with accuracy around 94%. Deep learning techniques applied in brain scan analysis achieves around 92% accuracy. Movement tests and setting smart environments to capture daily life behaviours are two potential future directions that may help discriminate dementia from normal aging. AI-based smart environments and multi-modal tests are promising future directions to improve detection of dementia in the earliest stages.

New horizons in late-onset essential tremor: a pre-cognitive biomarker of dementia?

Essential tremor (ET) is the most common cause of tremor in older adults. However, it is increasingly recognised that 30-50% of ET cases are misdiagnosed. Late-onset ET, when tremor begins after the age of 60, is particularly likely to be misdiagnosed and there is mounting evidence that it may be a distinct clinical entity, perhaps better termed 'ageing-related tremor'. Compared with older adults with early-onset ET, late-onset ET is associated with weak grip strength, cognitive decline, dementia and mortality. This raises questions around whether late-onset ET is a pre-cognitive biomarker of dementia and whether modification of dementia risk factors may be particularly important in this group. On the other hand, it is possible that the clinical manifestations of late-onset ET simply reflect markers of healthy ageing, or frailty, superimposed on typical ET. These issues are important to clarify, especially in the era of specialist neurosurgical treatments for ET being increasingly offered to older adults, and these may not be suitable in people at high risk of cognitive decline. There is a pressing need for clinicians to understand late-onset ET, but this is challenging when there are so few publications specifically focussed on this subject and no specific features to guide prognosis. More rigorous clinical follow-up and precise phenotyping of the clinical manifestations of late-onset ET using accessible computer technologies may help us delineate whether late-onset ET is a separate clinical entity and aid prognostication.

Get Parkinson's medications on time: the Leeds QI project.

Parkinson's disease (PD) is a common neurodegenerative disease. Delayed administration of PD medications is associated with increased risk of life-threatening complications including choking, aspiration pneumonia and neuroleptic malignant syndrome. In 2016, the spouse of a patient with PD wrote to Leeds Teaching Hospitals Trust (LTHT) to highlight that multiple medication delays and omissions had occurred during his recent admission. In response, LTHT formed a PD quality improvement (QI) Collaborative of multidisciplinary members committed to ensuring timely PD medication administration. The faculty used Institute for Healthcare Improvement Model for Improvement QI methodology. Interventions were tested on pilot wards and the most successful were scaled up and spread across all 90 adult inpatient wards as an 'intervention bundle'. Between January 2016 and June 2020 mean delays in the time from admission to first dose of medication dropped from over 7 to under 1 h. The mean percentage of omitted PD medications reduced from 15.1 to 0.6%. Project success was multifactorial but due to: Simplicity of interventions.Multiprofessional ownership by frontline teams to make changes and take prompt action.The spouse of the patient taking a leading role in the Collaborative, bringing her unique personal insight and experience, which facilitated behavioural change.

Health at the writing desk of John Ruskin: a study of handwriting and illness.

Though John Ruskin (1819-1900) is remembered principally for his work as a theorist, art critic and historian of visual culture, he wrote exhaustively about his health in his correspondence and diaries. Ruskin was prone to recurring depressive and hypochondriacal feelings in his youth and adulthood. In 1871, at the age of 52 years, he developed an illness with relapsing psychiatric and neurological features. He had a series of attacks of brain disturbance, and a deterioration of his mental faculties affected his writing for years before curtailing his career a decade before he died. Previous writers have suggested he had a psychiatric malady, perhaps schizophrenia or schizoaffective disorder. But the more obvious conclusion from a close medical reading of Ruskin's descriptions of his illness is he had some sort of 'organic' brain illness. This paper aims to give insight into the relationship between Ruskin's state of well-being and the features of his writing through a palaeographical study of his letters and diary entries. We examine the handwriting for physical traces of Ruskin's major brain illness, guided by the historical narrative of the illness. We also examine Ruskin's recording of his experiences for what they reveal about the failure of his health and its impact on his work. Ruskin's handwriting does not have clear-cut pathological features before around 1885, though suggestions of subtle writing deficits were present as early as 1876. After 1887, Ruskin's handwriting shows fixed pathological signs-tremor, disturbed letter formation and features that reflect a slow and laborious process of writing. These observations are more than could be explained by normal ageing, and suggest the presence of a neurological deficit affecting writing control. Our findings are consistent with conclusions that we drew from the historical record-that John Ruskin had an organic neurological disorder with cognitive, behavioural, psychiatric and motor effects.

Exercise and dementia prevention.

Ageing, genetic, medical and lifestyle factors contribute to the risk of Alzheimer's disease and other dementias. Around a third of dementia cases are attributable to modifiable risk factors such as physical inactivity, smoking and hypertension. With the rising prevalence and lack of neuroprotective drugs, there is renewed focus on dementia prevention strategies across the lifespan. Neurologists encounter many people with risk factors for dementia and are frequently asked whether lifestyle changes may help. Exercise has emerged as a key intervention for influencing cognition positively, including reducing the risk of age-related cognitive decline and dementia. This article focuses on the current evidence for physical inactivity as a modifiable dementia risk factor and aims to support neurologists when discussing risk reduction.

Multiple system atrophy mimicked by multi-organ pathology.

Both multiple system atrophy and Parkinson's disease may present with parkinsonism and autonomic dysfunction. We describe a patient who initially met the diagnostic criteria for multiple system atrophy and had atypical features for Parkinson's disease including blackouts and pyramidal signs. Ultimately, he was found to have three separate diagnoses rather than a single unifying one.

Multiple myeloma with multiple neurological presentations.

Multiple myeloma is a haematological malignancy with clonal plasma cell proliferation and production of monoclonal immunoglobulins. Its neurological complications are relatively common, caused by both the disease and the treatment. Neurologists should therefore be familiar with its neurological manifestations and complications. We describe a 40-year-old woman who presented with lower cranial neuropathies mimicking variant Guillain-Barré syndrome, with normal brain and spinal cord imaging and cerebrospinal fluid (CSF) albuminocytological dissociation, and subsequently diagnosed with IgD myeloma. She relapsed repeatedly with differing neurological presentations: numb chin syndrome and twice with impaired vision, first from cerebral venous sinus thrombosis and later from leptomeningeal infiltration of the optic chiasm. We discuss the neurological complications of myeloma, emphasising the need to consider it in a wide variety of neurological presentations and repeatedly to reassess its associated neurological diagnoses. We also highlight the complexity of myeloma treatment.

A New Evolutionary Algorithm-Based Home Monitoring Device for Parkinson's Dyskinesia.

Parkinson's disease (PD) is a neurodegenerative movement disorder. Although there is no cure, symptomatic treatments are available and can significantly improve quality of life. The motor, or movement, features of PD are caused by reduced production of the neurotransmitter dopamine. Dopamine deficiency is most often treated using dopamine replacement therapy. However, this therapy can itself lead to further motor abnormalities referred to as dyskinesia. Dyskinesia consists of involuntary jerking movements and muscle spasms, which can often be violent. To minimise dyskinesia, it is necessary to accurately titrate the amount of medication given and monitor a patient's movements. In this paper, we describe a new home monitoring device that allows dyskinesia to be measured as a patient goes about their daily activities, providing information that can assist clinicians when making changes to medication regimens. The device uses a predictive model of dyskinesia that was trained by an evolutionary algorithm, and achieves AUC>0.9 when discriminating clinically significant dyskinesia.

How to use pen and paper tasks to aid tremor diagnosis in the clinic.

When a patient presents with tremor, it can be useful to perform a few simple pen and paper tests. In this article, we explain how to maximise the value of handwriting and of drawing Archimedes spirals and straight lines as clinical assessments. These tasks take a matter of seconds to complete but provide a wealth of information that supplements the standard physical examination. They aid the diagnosis of a tremor disorder and can contribute to its longitudinal monitoring. Watching the patient's upper limb while they write and draw may reveal abnormalities such as bradykinesia, dystonic posturing and distractibility. The finished script and drawings can then be evaluated for frequency, amplitude, direction and symmetry of oscillatory pen movements and for overall scale of penmanship. Essential, dystonic, functional and parkinsonian tremor each has a characteristic pattern of abnormality on these pen and paper tests.

Functional dystonia and the borderland between neurology and psychiatry: New concepts.

Mind-brain dualism has dominated historical commentary on dystonia, a dichotomous approach that has left our conceptual grasp of it stubbornly incomplete. This is particularly true of functional dystonia, most diagnostically challenging of all functional movement disorders, in which the question of inherent psychogenicity remains a focus of debate. Phenomenological signs considered in isolation lack the specificity to distinguish organic and nonorganic forms, and dystonia's variability has frustrated attempts to develop objective laboratory-supported standards. Diagnostic criteria for functional dystonia that place emphasis on psychiatric symptoms perform poorly in studies of reliability, partly explained by the high frequency of psychopathology in organic dystonia. Novel approaches from the cognitive neurosciences may offer a way forward. Theory on Bayesian statistical prediction in cognitive processing is supported by sufficient experimental evidence for this model to be taken seriously as a way of reconciling contradictory notions about voluntary and unconscious motor control in functional movement disorders. In a Bayesian formulation of functional dystonia, misallocation of attention and abnormal predictive beliefs generate movements that are executed without a sense of agency. Building on this framework, there is a consensus that a biopsychosocial approach is required and that a unified philosophy of brain and mind is the best way to locate dystonia in the neurology-psychiatry borderland. At a practical level, movement disorder neurologists are best placed to differentiate organic from functional dystonia. The main role of psychiatrists is in the diagnosis and management of the primarily psychiatric disorders that often accompany dystonia. © 2016 International Parkinson and Movement Disorder Society.