Anatomical categorization of isolated non-focal dystonia: novel and existing patterns using a data-driven approach

According to expert consensus, dystonia can be classified as focal, segmental, multifocal, and generalized, based on the affected body distribution. To provide an empirical and data-driven approach to categorizing these distributions, we used a data-driven clustering approach to compare frequency and co-occurrence rates of non-focal dystonia in pre-defined body regions using the Dystonia Coalition (DC) dataset. We analyzed 1,618 participants with isolated non-focal dystonia from the DC database. The analytic approach included construction of frequency tables, variable-wise analysis using hierarchical clustering and independent component analysis (ICA), and case-wise consensus hierarchical clustering to describe associations and clusters for dystonia affecting any combination of eighteen pre-defined body regions. Variable-wise hierarchical clustering demonstrated closest relationships between bilateral upper legs (distance = 0.40), upper and lower face (distance = 0.45), bilateral hands (distance = 0.53), and bilateral feet (distance = 0.53). ICA demonstrated clear grouping for the a) bilateral hands, b) neck, and c) upper and lower face. Case-wise consensus hierarchical clustering at k = 9 identified 3 major clusters. Major clusters consisted primarily of a) cervical dystonia with nearby regions, b) bilateral hand dystonia, and c) cranial dystonia. Our data-driven approach in a large dataset of isolated non-focal dystonia reinforces common segmental patterns in cranial and cervical regions. We observed unexpectedly strong associations between bilateral upper or lower limbs, which suggests that symmetric multifocal patterns may represent a previously underrecognized dystonia subtype.

Effects of ventral intermediate nucleus deep brain stimulation across multiple effectors in essential tremor

OBJECTIVE

Essential tremor (ET) prominently affects the upper-limbs during voluntary movements, but can also affect the lower-limbs, head, and chin. Although deep brain stimulation (DBS) of the ventral intermediate nucleus (VIM) of thalamus improves both clinical ratings and quantitative measures of tremor, no study has quantified effects of DBS on tremor across multiple body parts. Our objective was to quantify therapeutic effects of DBS across multiple body parts in ET.

METHODS

We performed quantitative assessment of tremor in ET patients who had DBS for at least one year. We assessed tremor on and off VIM-stimulation using triaxial accelerometers on the upper-limbs, lower-limbs, head and chin during seated and standing tasks.

RESULTS

VIM-DBS significantly reduced tremor, but there was no statistical difference in degree of tremor reduction across the measured effectors. Compared to healthy controls, ET patients treated with DBS showed significantly greater tremor power (4-8 Hz) across all effectors during seated and standing tasks.

CONCLUSIONS

VIM-DBS reduced tremor in ET patients. There was no significant difference in the degree of tremor reduction across the measured effectors.

SIGNIFICANCE

This study provides new quantitative evidence that VIM-DBS is effective at reducing tremor across multiple parts of the body.

B-26 Predictors of Cognitive Decline Over a 2-year Follow up: Olfaction and Scans Without Evidence of Dopaminergic Deficit Status (SWEDD)

Objective

Given the high discriminatory power of olfaction assessments in movement disorders, the current study sought to determine whether olfaction dysfunction differentially predicted cognitive decline in patients who have scans without evidence of dopaminergic deficit (SWEDD). Dopamine depletion is a major neuropathological feature of Parkinson’s disease (PD); however, 15% of patients with a clinical PD diagnosis have neuroimaging evidence of intact dopaminergic function. Recent work has suggested that patients with SWEDD are at a greater risk of cognitive impairment relative to those with PD.

Methods

Archival data were obtained from the Parkinson’s Progression Markers Initiative database. The total sample included three groups: PD (n = 401), SWEDD (n = 51), and HC (n = 175). Participants were categorized into non-impaired (-) or impaired (+) olfaction groups based on performance on the University of Pennsylvania Smell Identification Test, corrected for age and gender. Participants were administered the Montreal Cognitive Assessment twice and change scores were calculated to examine changes in cognition over time (baseline – two-year follow-up).

Results

A bootstrapped analysis of variance (ANOVA) revealed that the SWEDD+ group had lower MoCA scores than PD+ and HC+ groups at baseline (ps < .05). A bootstrapped ANOVA indicated that group differences were not significant at follow-up; rather, impaired baseline olfaction predicted cognitive decline across all study participants (p < .05), regardless of diagnosis.

Conclusions

Future studies are needed to assess whether the profile of motor and non-motor symptoms in SWEDD patients, including olfaction, is deserving of its own syndrome, or whether individual patients may fit better under alternative, existing diagnoses.

High rates of fatigue and sleep disturbances in dystonia

BACKGROUND

Nonmotor symptoms in dystonia are increasingly recognized to impair the quality of life. The primary objective of this study was to determine the prevalence of fatigue and sleep disturbances in dystonia and to ascertain their impact on quality of life using standardized questionnaires.

METHODS

Dystonia patients presenting to a Botulinum toxin clinic were prospectively administered Fatigue Severity Scale (FSS), Multidimensional Fatigue Inventory (MFI), Epworth Sleepiness Scale (ESS) and Parkinson's Disease Sleep Scale (PDSS) for assessment of fatigue and sleep disturbances. Health-related Quality of life (HRQOL) was determined using MOS SF-36 scale and depressive symptoms were assessed using the Beck Depression Inventory II.

RESULTS

Ninety-one patients with dystonia participated (66 women, 25 men, mean age 60 ± 17 years). Nine subjects had generalized dystonia, 18 segmental dystonia and 64 had focal dystonia. Moderate to severe fatigue was present in 43% of the cohort (FSS), excessive daytime somnolence in 27% (ESS) and other sleep disturbances in 26% (PDSS). FSS and MFI scores correlated significantly with HRQOL even when controlled for depression and sleep disturbances. Excessive daytime somnolence and nocturnal sleep disturbances correlated significantly with the HRQOL; however, these effects were not seen for daytime somnolence when controlled for depression. Psychometric testing found adequate reliabilities and convergent validities for both fatigue and sleep scales.

CONCLUSION

Fatigue and sleep disturbances revealed high prevalence rates in this large, first of its dystonia study. They negatively impacted the quality of life even when controlled for comorbid depression.