Gaussian Process-based prediction of memory performance and biomarker status in ageing and Alzheimer's disease-A systematic model evaluation.

Neuroimaging markers based on Magnetic Resonance Imaging (MRI) combined with various other measures (such as genetic covariates, biomarkers, vascular risk factors, neuropsychological tests etc.) might provide useful predictions of clinical outcomes during the progression towards Alzheimer's disease (AD). The use of multiple features in predictive frameworks for clinical outcomes has become increasingly prevalent in AD research. However, many studies do not focus on systematically and accurately evaluating combinations of multiple input features. Hence, the aim of the present work is to explore and assess optimal combinations of various features for MR-based prediction of (1) cognitive status and (2) biomarker positivity with a multi-kernel learning Gaussian process framework. The explored features and parameters included (A) combinations of brain tissues, modulation, smoothing, and image resolution; (B) incorporating demographics & clinical covariates; (C) the impact of the size of the training data set; (D) the influence of dimensionality reduction and the choice of kernel types. The approach was tested in a large German cohort including 959 subjects from the multicentric longitudinal study of cognitive impairment and dementia (DELCODE). Our evaluation suggests the best prediction of memory performance was obtained for a combination of neuroimaging markers, demographics, genetic information (ApoE4) and CSF biomarkers explaining 57% of outcome variance in out-of-sample predictions. The highest performance for Aß42/40 status classification was achieved for a combination of demographics, ApoE4, and a memory score while usage of structural MRI further improved the classification of individual patient's pTau status.

Epidemiological, clinical and genetic aspects of adult onset isolated focal dystonia in Ireland.

BACKGROUND: Adult onset idiopathic isolated focal dystonia presents with a number of phenotypes. Reported prevalence rates vary considerably; well-characterized cohorts are important to our understanding of this disorder. AIM: To perform a nationwide epidemiological study of adult onset idiopathic isolated focal dystonia in the Republic of Ireland. METHODS: Patients with adult onset idiopathic isolated focal dystonia were recruited from multiple sources. Diagnosis was based on assessment by a neurologist with an expertise in movement disorders. When consent was obtained, a number of clinical features including family history were assessed. RESULTS: On the prevalence date there were 592 individuals in Ireland with adult onset idiopathic isolated focal dystonia, a point prevalence of 17.8 per 100 000 (95% confidence interval 16.4-19.2). Phenotype numbers were cervical dystonia 410 (69.2%), blepharospasm 102 (17.2%), focal hand dystonia 39 (6.6%), spasmodic dysphonia 18 (3.0%), musician's dystonia 17 (2.9%) and oromandibular dystonia six (1.0%). Sixty-two (16.5%) of 375 consenting index cases had a relative with clinically confirmed adult onset idiopathic isolated focal dystonia (18 multiplex and 24 duplex families). Marked variations in the proportions of patients with tremor, segmental spread, sensory tricks, pain and psychiatric symptoms by phenotype were documented. CONCLUSIONS: The prevalence of adult onset idiopathic isolated focal dystonia in Ireland is higher than that recorded in many similar service-based epidemiological studies but is still likely to be an underestimate. The low proportion of individuals with blepharospasm may reflect reduced environmental exposure to sunlight in Ireland. This study will serve as a resource for international comparative studies of environmental and genetic factors in the pathogenesis of the disorder.

Temporal discrimination thresholds in adult-onset primary torsion dystonia: an analysis by task type and by dystonia phenotype.

Adult-onset primary torsion dystonia (AOPTD) is an autosomal dominant disorder with markedly reduced penetrance. Sensory abnormalities are present in AOPTD and also in unaffected relatives, possibly indicating non-manifesting gene carriage (acting as an endophenotype). The temporal discrimination threshold (TDT) is the shortest time interval at which two stimuli are detected to be asynchronous. We aimed to compare the sensitivity and specificity of three different TDT tasks (visual, tactile and mixed/visual-tactile). We also aimed to examine the sensitivity of TDTs in different AOPTD phenotypes. To examine tasks, we tested TDT in 41 patients and 51 controls using visual (2 lights), tactile (non-painful electrical stimulation) and mixed (1 light, 1 electrical) stimuli. To investigate phenotypes, we examined 71 AOPTD patients (37 cervical dystonia, 14 writer's cramp, 9 blepharospasm, 11 spasmodic dysphonia) and 8 musician's dystonia patients. The upper limit of normal was defined as control mean +2.5 SD. In dystonia patients, the visual task detected abnormalities in 35/41 (85%), the tactile task in 35/41 (85%) and the mixed task in 26/41 (63%); the mixed task was less sensitive than the other two (p = 0.04). Specificity was 100% for the visual and tactile tasks. Abnormal TDTs were found in 36 of 37 (97.3%) cervical dystonia, 12 of 14 (85.7%) writer's cramp, 8 of 9 (88.8%) blepharospasm, 10 of 11 (90.1%) spasmodic dysphonia patients and 5 of 8 (62.5%) musicians. The visual and tactile tasks were found to be more sensitive than the mixed task. Temporal discrimination threshold results were comparable across common adult-onset primary torsion dystonia phenotypes, with lower sensitivity in the musicians.