The final blink: intact cerebellar associative learning in isolated dystonia

Impaired eyeblink conditioning is often cited as evidence for cerebellar dysfunction in isolated dystonia. However, the results from individual studies are conflicting and underpowered. This collaborative project collated all published data and systematically re-examined the contribution of the predictors dystonia and its subtypes within a statistical model which controlled for the co-variates age and sex. Original neurophysiological data were shared and a sex and age matched control group were collected (dystonia n=52, controls n=50). Two raters blinded to participant identity rescored all recordings (6732 trials). After high inter-rater agreement was confirmed, mean conditioning per block was entered into a mixed repetitive measures model to evaluate the influence of sex, age, dystonia subtype (focal hand dystonia, cervical dystonia, DYT-TOR1A and DYT-THAP1) and clinical features such as tremor. There was a wide range of conditioning behavior across individuals in both groups. Young age (p=0.031) was associated with higher conditioning. All dystonia versus controls showed no difference in conditioning (p=0.517). Analysis of dystonia subgroup, with age and sex as co-variates, showed that conditioning in cervical dystonia, focal hand dystonia and DYT-TOR1A was comparable to controls. DYT-THAP1 was characterized by high levels of conditioning. Clinical features such as tremor did not significantly influence conditioning. Sample size estimates for future work are provided based on the variance observed. Eyeblink conditioning, a proxy for cerebellar function, appears intact in the subtypes of isolated dystonia examined. Precise mechanisms for how the cerebellum interplays mechanistically with other key neuroanatomical nodes within the dystonic network remains elusive.

Personality Profile in Focal Hand Dystonia: A Cross-Sectional Study

It has been suggested that focal hand dystonia (FHD) should be viewed as a neuropsychiatric disorder rather than as a pure movement disorder. We aimed to compare the personality factors that are common to people with FHD and evaluate how personality factors could affect the functionality of the upper limbs and community participation. We conducted a cross-sectional case–control study in which 12 people with FHD were matched with 12 age and gender matched healthy control participants. The Big Five Questionnaire; the Quick Disabilities, Arm, Shoulder, and Hand questionnaire; and the Jebsen–Taylor Test of Hand Function were used as assessment measures. Control of emotions was the only variable for which a significant difference was found, with participants with FHD displaying lesser control. Correlations were not observed between different personality profiles, the functionality of the upper limb,s and the perceived participation of people with FHD in activities of daily living. People with FHD may present with low emotional stability, but this does not have a negative impact on the functionality of the upper limbs and activities of daily living. These findings have clinical implications to be considered for interventions, as they suggest that personality aspects, such as extraversion, may not predict for better functionality and perceived participation in activities of daily living.