Impaired Touchscreen Skills in Parkinson's Disease and Effects of Medication.

BACKGROUND: Deficits in fine motor skills may impair device manipulation including touchscreens in people with Parkinson's disease (PD). OBJECTIVES: To investigate the impact of PD and anti-parkinsonian medication on the ability to use touchscreens. METHODS: Twelve PD patients (H&Y II-III), OFF and ON medication, and 12 healthy controls (HC) performed tapping, single and multi-direction sliding tasks on a touchscreen and a mobile phone task (MPT). Task performance was compared between patients (PD-OFF, PD-ON) and HC and between medication conditions. RESULTS: Significant differences were found in touchscreen timing parameters, while accuracy was comparable between groups. PD-OFF needed more time than HC to perform single (P = 0.048) and multi-direction (P = 0.004) sliding tasks and to grab the dot before sliding (i.e., transition times) (P = 0.040; P = 0.004). For tapping, dopaminergic medication significantly increased performance times (P = 0.046) to comparable levels as those of HC. However, for the more complex multi-direction sliding, movement times remained slower in PD than HC irrespective of medication intake (P < 0.050 during ON and OFF). The transition times for the multi-direction sliding task was also higher in PD-ON than HC (P = 0.048). Touchscreen parameters significantly correlated with MPT performance, supporting the ecological validity of the touchscreen tool. CONCLUSIONS: PD patients show motor problems when manipulating touchscreens, even when optimally medicated. This hinders using mobile technology in daily life and has implications for developing adequate E-health applications for this group. Future work needs to establish whether touchscreen training is effective in PD.

Retention of touchscreen skills is compromised in Parkinson's disease.

Fine motor skill impairments likely have a severe impact on the use of touchscreens in Parkinson's disease (PD). Although recent work showed positive effects of intensive writing training, many questions remained regarding the consolidation of motor learning in PD. The current study examined the effects of PD on practicing the manipulation of touchscreen technology and whether this can lead to 24h-retention and transfer. We developed the Swipe-Slide Pattern (SSP)-task, similar to handling a touchscreen unlock-trace. On day 1, 11 patients and 10 healthy, age-matched controls underwent two consecutive runs of early and late learning (9 × 36 s SSP and 36 s rest). This was followed by a retention test after 24 h, including the assessment of transfer. Movement time (MT, s), Euclidean distance (ED) and a performance index (PI = MT/ED) were compared across the learning phases (early, late, retention and transfer) for both groups. Additionally, a learning, retention and transfer index were compared between groups and correlated to clinical characteristics. Both groups significantly improved in MT and PI across practice. However, while healthy adults showed further improvements after a 24h-retention period, patients presented with impaired retention indices. This was correlated with disease duration, disease severity and performance on a daily life mobile phone task. Finally, transfer to a similar, but untrained pattern was comparable between both groups. Overall, short-term practice of the SSP-task results in improvements for PD patients, albeit with impaired retention. Future work should investigate whether prolonged touchscreen skill training can be retained in motor memory in PD.

When motor control gets out of hand: Speeding up triggers freezing in the upper limb in Parkinson's disease.

INTRODUCTION: Patients with Parkinson's disease (PD) can suffer from sudden movement arrests during upper limb tasks. The current study investigated a test to assess freezing of the upper limbs (FOUL) at two speed conditions to improve the sensitivity of FOUL detection. METHODS: Forty-nine patients with PD and 10 age-matched controls (HC) performed a freezing-provoking writing task, requiring up- and down-stroke writing at varying sizes in-between visual target zones indicating funnel-shapes on a touch-sensitive tablet. They performed five trials at their preferred speed, referred to as the Normal Funnel Task (NFT) and five trials at maximum speed, referred to as the Fast Funnel Task (FFT), in a random order. RESULTS: Based on a combination of kinematic criteria and video analysis, 183 FOUL episodes were detected in 24 participants (23 PD, 1 HC). The number of patients with FOUL, number of FOUL episodes and percentage time frozen were significantly higher during FFT than NFT. Most FOUL episodes occurred during writing at small (51.6%) and decreasing size (36.3%). Additionally, FOUL outcomes significantly correlated with the Montreal Cognitive Assessment and New Freezing of Gait Questionnaire. CONCLUSION: As FOUL is more prevalent under higher task demands, these data offer support for the "threshold model", previously proposed to provide insight in freezing of gait (FOG) and underscoring the presupposed link between FOG and FOUL. As well, this study may provide a novel paradigm to assess FOUL in both laboratory and clinical settings.

Does transcranial direct current stimulation during writing alleviate upper limb freezing in people with Parkinson's disease? A pilot study.

Transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) can boost motor performance in Parkinson's disease (PD) when it is applied at rest. However, the potential supplementary therapeutic effect of the concurrent application of tDCS during the training of motor tasks is largely unknown. The present study examined the effects of tDCS on upper limb motor blocks during a freezing-provoking writing task (the funnel task) requiring up- and down-stroke movements at alternating amplitudes. Ten PD patients and 10 age-matched controls underwent two sessions of writing combined with 20 min of anodal or sham tDCS on the left M1 in a randomized cross-over design. The primary outcome was the number of upper limb freezing episodes during five trials of the funnel task on a touch-sensitive tablet. PD patients showed a significant reduction in freezing episodes during tDCS compared to sham. No effects of tDCS were found for the amplitude, variability and speed of the strokes outside the freezing episodes. However, patients who reported freezing episodes in daily life (N = 6) showed a beneficial effect of tDCS on stroke characteristics. These results indicate a subgroup-dependent variability in response to non-invasive brain stimulation applied during the performance of motor tasks in PD. This warrants future studies to examine tDCS as an adjuvant tool for training programs aimed to reduce motor deficits related to freezing.

Determinants of Dual-Task Training Effect Size in Parkinson Disease: Who Will Benefit Most?

BACKGROUND AND PURPOSE: Dual-task interventions show positive effects in people with Parkinson disease (PD), but it remains unclear which factors determine the size of these benefits. As a secondary analysis of the DUALITY trial, the aim of this study was to assess the determinants of the effect size after 2 types of dual-task practice. METHODS: We randomly allocated 121 participants with PD to receive either integrated or consecutive dual-task training. Dual-task walking performance was assessed during (i) a backward digit span task (digit), (ii) an auditory Stroop task (Stroop), and (iii) a functional mobile phone task. Baseline descriptive, motor, and cognitive variables were correlated with the change in dual-task gait velocity after the intervention. Factors correlated with the change in dual-task gait velocity postintervention (P < 0.20) were entered into a stepwise forward multiple linear regression model. RESULTS: Lower dual-task gait velocity and higher cognitive capacity (Scales for Outcomes in Parkinson's Disease-Cognition [ScopaCog]) at baseline were related to larger improvements in dual-task gait velocity after both integrated and consecutive dual-task training for all 3 tasks (ß[gait] = -0.45, ß[ScopaCog] = 0.34, R = 0.23, P < 0.001, for digit; ß[gait] = -0.52, ß[ScopaCog] = 0.29, R = 0.26, P < 0.001, for Stroop; and ß[gait] = -0.40, ß[ScopaCog] = 0.30, R = 0.18, P < 0.001, for mobile phone task). DISCUSSION AND CONCLUSIONS: Participants with PD who showed a slow dual-task gait velocity and good cognitive functioning at baseline benefited most from the dual-task training, irrespective of the type of training and type of dual-task outcome.Video Abstract available for more insights from the authors (see Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A242).

Adaptations to Postural Perturbations in Patients With Freezing of Gait.

Introduction: Freezing of gait (FOG) is a powerful determinant of falls in Parkinson's disease (PD). Automatic postural reactions serve as a protective strategy to prevent falling after perturbations. However, differences in automatic postural reactions between patients with and without FOG in response to perturbation are at present unclear. Therefore, the present study aimed to compare the response patterns and neuromuscular control between PD patients with and without FOG and healthy controls (HCs) after postural perturbations. Methods: 28 PD patients (15 FOG+, 13 FOG-) and 22 HCs were included. Participants stood on a moveable platform while random perturbations were imposed. The first anterior platform translation was retained for analysis. Center of pressure (CoP) and center of mass (CoM) trajectories and trunk, knee and ankle angles were compared between the three groups using the Statistical Parametric Mapping technique, allowing to capture changes in time. In addition, muscle activation of lower leg muscles was measured using EMG. Results: At baseline, FOG+ stood with more trunk flexion than HCs (p = 0.005), a result not found in FOG-. Following a perturbation, FOG+ reacted with increased trunk extension (p = 0.004) in comparison to HCs, a pattern not observed in FOG-. The CoM showed greater backward displacement in FOG- and FOG+ (p = 0.008, p = 0.027). Both FOG+ and FOG- showed increased co-activation of agonist and antagonist muscles compared to HCs (p = 0.010), with no differences between FOG+ and FOG-. Conclusions: Automatic postural reactions after a sudden perturbation are similar between PD subgroups with and without FOG but different from HCs. Reactive postural control, largely regulated by brain stem centers, seems to be modulated by different mechanisms than those governing freezing of gait. Greater differences in initial stance position, enhanced by joint stiffening, could however underlie maladaptive postural responses and increase susceptibility for balance loss in FOG+ compared to FOG-.

Training for Micrographia Alters Neural Connectivity in Parkinson's Disease.

Despite recent advances in clarifying the neural networks underlying rehabilitation in Parkinson's disease (PD), the impact of prolonged motor learning interventions on brain connectivity in people with PD is currently unknown. Therefore, the objective of this study was to compare cortical network changes after 6 weeks of visually cued handwriting training (= experimental) with a placebo intervention to address micrographia, a common problem in PD. Twenty seven early Parkinson's patients on dopaminergic medication performed a pre-writing task in both the presence and absence of visual cues during behavioral tests and during fMRI. Subsequently, patients were randomized to the experimental (N = 13) or placebo intervention (N = 14) both lasting 6 weeks, after which they underwent the same testing procedure. We used dynamic causal modeling to compare the neural network dynamics in both groups before and after training. Most importantly, intensive writing training propagated connectivity via the left hemispheric visuomotor stream to an increased coupling with the supplementary motor area, not witnessed in the placebo group. Training enhanced communication in the left visuomotor integration system in line with the learned visually steered training. Notably, this pattern was apparent irrespective of the presence of cues, suggesting transfer from cued to uncued handwriting. We conclude that in early PD intensive motor skill learning, which led to clinical improvement, alters cortical network functioning. We showed for the first time in a placebo-controlled design that it remains possible to enhance the drive to the supplementary motor area through motor learning.

Being on Target: Visual Information during Writing Affects Effective Connectivity in Parkinson's Disease.

A common motor symptom of Parkinson's disease (PD) is micrographia, characterized by a decrease in writing amplitude. Despite the relevance of this impairment for activities of daily living, the underlying neural network abnormalities and the impact of cueing strategies on brain connectivity are unknown. Therefore, we investigated the effects of visual cues on visuomotor network interactions during handwriting in PD and healthy controls (HCs). Twenty-eight patients with early disease, ON dopaminergic medication, and 14 age-matched controls performed a pre-writing task with and without visual cues in the scanner. Patients displayed weaker right visuo-parietal coupling than controls, suggesting impaired visuomotor integration during writing. Surprisingly, cueing did not have the expected positive effects on writing performance. Patients and controls, however, did activate similar networks during cued and uncued writing. During cued writing, the stronger influence of both visual and motor areas on the left superior parietal lobe suggested that visual cueing induced greater visual steering. In the absence of cues, there was enhanced coupling between parietal and supplementary motor areas (SMA) in line with previous findings in HCs during uncued motor tasks. In conclusion, the present study showed that patients with PD, despite their compromised brain function, were able to shift neural networks similar to controls. However, it seemed that visual cues provided a greater accuracy constraint on handwriting rather than offering unequivocal beneficial effects. Altogether, the results suggest that the effectiveness of using compensatory neural networks through applying external stimuli is task dependent and may compromise motor control during writing.

Cueing for people with Parkinson's disease with freezing of gait: A narrative review of the state-of-the-art and novel perspectives.

Freezing, which manifests during gait and other movements, is an incapacitating motor symptom experienced by many patients with Parkinson's disease (PD). In rehabilitation, auditory and visual cueing methods are commonly applied to evoke a more goal-directed type of motor control and, as such, reduce freezing severity in patients with PD. In this narrative review, we summarize the current evidence regarding the effects of external cueing in patients with PD with freezing of gait (FOG) and provide suggestions on how to further improve cueing effectiveness with emerging technological developments. For this paper, we reviewed 24 articles describing the assessment of the effects of cues in patients with FOG (n=354). Because these studies mostly involved quasi-experimental designs, no methodological analysis was undertaken. In general, the evidence suggests that cue-augmented training can reduce FOG severity, improve gait parameters and improve upper-limb movements immediately after training. However, findings were not univocal, and long-term consolidation and transfer of the effects appear to be hampered specifically in this subgroup. With the increasing use of wearable technology, new possibilities are allowing for adapting the cue type, cue content and dose of cues to the needs of individual patients, which may boost the clinical use and efficiency of cued training in PD patients with FOG.

Altered effective connectivity contributes to micrographia in patients with Parkinson's disease and freezing of gait.

Recently, it was shown that patients with Parkinson's disease (PD) and freezing of gait (FOG) can also experience freezing episodes during handwriting and present writing problems outside these episodes. So far, the neural networks underlying increased handwriting problems in subjects with FOG are unclear. This study used dynamic causal modeling of fMRI data to investigate neural network dynamics underlying freezing-related handwriting problems and how these networks changed in response to visual cues. Twenty-seven non-freezers and ten freezers performed a pre-writing task with and without visual cues in the scanner with their right hand. The results showed that freezers and non-freezers were able to recruit networks involved in cued and uncued writing in a similar fashion. Whole group analysis also revealed a trend towards altered visuomotor integration in patients with FOG. Next, we controlled for differences in disease severity between both patient groups using a sensitivity analysis. For this, a subgroup of ten non-freezers matched for disease severity was selected by an independent researcher. This analysis further exposed significantly weaker coupling in mostly left hemispheric visuo-parietal, parietal - supplementary motor area, parietal - premotor, and premotor-M1 pathways in freezers compared to non-freezers, irrespective of cues. Correlation analyses revealed that these impairments in connectivity were related to writing amplitude and quality. Taken together, these findings show that freezers have reduced involvement of the supplementary motor area in the motor network, which explains the impaired writing amplitude regulation in this group. In addition, weaker supportive premotor connectivity may have contributed to micrographia in freezers, a pattern that was independent of cueing.

Handwriting training in Parkinson's disease: A trade-off between size, speed and fluency.

BACKGROUND: In previous work, we found that intensive amplitude training successfully improved micrographia in Parkinson's disease (PD). Handwriting abnormalities in PD also express themselves in stroke duration and writing fluency. It is currently unknown whether training changes these dysgraphic features. OBJECTIVE: To determine the differential effects of amplitude training on various hallmarks of handwriting abnormalities in PD. METHODS: We randomized 38 right-handed subjects in early to mid-stage of PD into an experimental group (n = 18), receiving training focused at improving writing size during 30 minutes/day, five days/week for six weeks, and a placebo group (n = 20), receiving stretch and relaxation exercises at equal intensity. Writing skills were assessed using a touch-sensitive tablet pre- and post-training, and after a six-week retention period. Tests encompassed a transfer task, evaluating trained and untrained sequences, and an automatization task, comparing single- and dual-task handwriting. Outcome parameters were stroke duration (s), writing velocity (cm/s) and normalized jerk (i.e. fluency). RESULTS: In contrast to the reported positive effects of training on writing size, the current results showed increases in stroke duration and normalized jerk after amplitude training, which were absent in the placebo group. These increases remained after the six-week retention period. In contrast, velocity remained unchanged throughout the study. CONCLUSION: While intensive amplitude training is beneficial to improve writing size in PD, it comes at a cost as fluency and stroke duration deteriorated after training. The findings imply that PD patients can redistribute movement priorities after training within a compromised motor system.

Freezing-related perception deficits of asymmetrical walking in Parkinson's disease.

Patients with Parkinson's disease (PD), and especially those with freezing of gait (FOG), are known to experience impairments in gait rhythmicity, symmetry, and bilateral coordination between both legs. In the current study, we investigated whether deficits in perception of gait speed between limbs were more pronounced in freezers than in non-freezers and could explain some of these gait impairments. We also assessed cognitive ability and proprioception. Twenty-five PD patients (13 freezers, 12 non-freezers) and 12 healthy controls walked on a split-belt treadmill, while the speed of one of the belts was gradually increased. Participants had to indicate the moment at which they perceived belt speeds to be different. The main outcome variables were the number of correct responses (perception accuracy) and the difference in belt speeds at the moment the participants perceived belt speeds to be different (perception threshold). In addition, gait characteristics during both split- and tied-belt walking were determined. Results showed significantly lower perception accuracy in freezers, whereas the perception threshold did not differ between groups. During tied-belt walking, freezers exhibited more asymmetrical step lengths and limb excursions than non-freezers and healthy controls. Greater step length and limb excursions were associated with better perception, whereas more variable gait was associated with more impaired perception. The results confirm the hypothesis that freezers have impaired perception of locomotor asymmetry. While proprioceptive and cognitive ability did not explain these findings, the possible causal link with the occurrence of FOG needs further corroboration.

Focusing on heel strike improves toe clearance in people with Parkinson's disease: an observational pilot study.

OBJECTIVES: To investigate differences in toe clearance between people with PD and age-matched healthy elderly (HE) during comfortable walking and to study the effects of dual-tasking and the use of an attentional strategy emphasizing heel strike on toe clearance. DESIGN: Observational cross-sectional study. SETTING: Camera-based 3D gait laboratory. PARTICIPANTS: Ten persons with PD (Hoehn and Yahr I to III) having mild gait disturbances and 10 HE. INTERVENTIONS: Participants walked for two minutes under three conditions at comfortable pace: single-task walking, attending to heel strike during single-task walking, and dual-task walking. MAIN OUTCOME MEASURES: Minimal and maximal toe clearance; foot strike angle with the ground. RESULTS: People with PD had less maximal toe clearance in the end of the swing phase and a smaller foot strike angle than HE during all three walking conditions. Impairments significantly diminished during heel strike focused walking improving performance to equal the HE. Heel strike focused walking resulted in an increased minimal toe clearance and a longer duration of end swing phase when compared to walking with and without a dual-task. The attentional strategy to focus on heel strike improved the stride length when compared to dual-task walking. Surprisingly, minimal toe clearance did not differ between PD and HE in any of the conditions and there were no dual-task effects on toe clearance. CONCLUSION: These findings provide evidence favoring the potential incorporation of an attentional strategy focusing on the heel strike in PD gait rehabilitation.

External input for gait in people with Parkinson's disease with and without freezing of gait: One size does not fit all.

Cueing or feedback provided when gait deviates from a predefined goal (intelligent input) can now be provided with wearable technology for Parkinson's disease (PD). As people with and without freezing of gait (FOG) have distinct cognitive profiles, they may respond differently to various types of input. This study compared the effects of four input modalities during prolonged walking and explored the relationship with cognition, subjective preference, and FOG. Participants (15 with and 13 without FOG) walked 30 min while exposed to continuous cueing; intelligent cueing; intelligent feedback; or no input. Cueing consisted of metronome beats matched to comfortable cadence. Intelligent input represented bouts of ten beats indicating comfortable cadence (intelligent cueing) or an instruction to adapt gait speed (intelligent feedback) when cadence deviated from the comfortable target. Preference for one condition over the other was gathered. Freezers produced most stable gait under continuous cueing, but the majority favored intelligent feedback. Non-freezers showed no differences between conditions, but gait was more stable under intelligent input than in freezers. Interestingly, lower cognitive scores were related to worse gait during intelligent input, most prominently seen in freezers. These results suggest that cognitive ability is an aspect to take into account when deciding on the most appropriate cueing modality in different PD subgroups.

Clinical balance scales indicate worse postural control in people with Parkinson's disease who exhibit freezing of gait compared to those who do not: A meta-analysis.

Postural instability and freezing of gait (FOG) are key features of Parkinson's disease (PD) that are closely related to falls. Uncovering the postural control differences between individuals with and without FOG contributes to our understanding of the relationship between these phenomena. The objective of this meta-analysis was to investigate whether postural control deficits, as detected by clinical balance scales, were more apparent in FOG+ compared to FOG-. Furthermore, we aimed to identify whether different scales were equally sensitive to detect postural control deficits and whether medication affected postural control differentially in each subgroup. Relevant articles were identified via five electronic databases. We performed a meta-analysis on nine studies which reported clinical balance scale scores in 249 freezers and 321 non-freezers. Methodological analysis showed that in 5/9 studies disease duration differed between subgroups. Despite this drawback, postural control was found to be significantly worse in FOG+ compared to FOG-. All included clinical balance scales were found to be sufficiently sensitive to detect the postural control differences. Levodopa did not differentially affect postural control (p=0.21), as in both medication states FOG+ had worse postural stability than FOG-. However, this finding warrants a cautious interpretation given the limitations of the studies included. From subscore analysis, we found that reactive and dynamic postural control were the most affected postural control systems in FOG+. We conclude that our findings provide important evidence for pronounced postural instability in individuals with FOG, which can be easily picked up with clinical evaluation tools. Posturographic measures in well-matched subgroups are needed to highlight the exact nature of these deficits.

Prolonged Walking with a Wearable System Providing Intelligent Auditory Input in People with Parkinson's Disease.

Rhythmic auditory cueing is a well-accepted tool for gait rehabilitation in Parkinson's disease (PD), which can now be applied in a performance-adapted fashion due to technological advance. This study investigated the immediate differences on gait during a prolonged, 30 min, walk with performance-adapted (intelligent) auditory cueing and verbal feedback provided by a wearable sensor-based system as alternatives for traditional cueing. Additionally, potential effects on self-perceived fatigue were assessed. Twenty-eight people with PD and 13 age-matched healthy elderly (HE) performed four 30 min walks with a wearable cue and feedback system. In randomized order, participants received: (1) continuous auditory cueing; (2) intelligent cueing (10 metronome beats triggered by a deviating walking rhythm); (3) intelligent feedback (verbal instructions triggered by a deviating walking rhythm); and (4) no external input. Fatigue was self-scored at rest and after walking during each session. The results showed that while HE were able to maintain cadence for 30 min during all conditions, cadence in PD significantly declined without input. With continuous cueing and intelligent feedback people with PD were able to maintain cadence (p = 0.04), although they were more physically fatigued than HE. Furthermore, cadence deviated significantly more in people with PD than in HE without input and particularly with intelligent feedback (both: p = 0.04). In PD, continuous and intelligent cueing induced significantly less deviations of cadence (p = 0.006). Altogether, this suggests that intelligent cueing is a suitable alternative for the continuous mode during prolonged walking in PD, as it induced similar effects on gait without generating levels of fatigue beyond that of HE.

Influence of Cueing and an Attentional Strategy on Freezing of Gait in Parkinson Disease During Turning.

BACKGROUND AND PURPOSE: Individuals with Parkinson disease exhibit decreased axial head-pelvis rotation. Consequently, they turn more en bloc than healthy controls, which may contribute to freezing during turning. We wanted to understand the influence of auditory cueing and an attentional strategy on turning and how this related to freezing of gait (FOG). METHODS: Fifteen participants with Parkinson disease and FOG were asked to turn 180° during baseline condition, unilateral cueing, and an attentional strategy prompting to start the turn with head rotation first. FOG occurrence, axial rotation, center of mass (COM) deviation, knee-flexion amplitude, and total turn velocity were measured using 3D motion analysis while off-medication. Normal reference values were obtained from 14 age-matched controls. RESULTS: Thirty-nine FOG episodes occurred in 5 participants. FOG occurred in 52.8% of baseline trials compared with 34.6% of trials using the head-first strategy, and 3.8% of the auditory cueing trials. During the head first strategy, the initiation of head, trunk, and pelvic rotation as well as the head-pelvis separation resembled turning patterns of healthy controls, but the COM shift to the inside of the turn was exaggerated. By contrast, during cueing, turning became more en bloc, with decreased head-pelvis separation and knee-flexion amplitude. DISCUSSION AND CONCLUSIONS: Cueing reduced FOG but did not correct axial movement deficits. The head-first strategy improved head-pelvis dissociation but had only limited effects on FOG. These results suggest that axial and COM deviation impairments are not directly related to FOG but may rather indicate a compensatory mechanism. Cueing reinforced the en-bloc movement and might as such help prevent FOG by triggering an alternative neural mechanism for movement generation.Video Abstract available for more insights from the authors (see Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A163).

Validity and reliability of a new tool to evaluate handwriting difficulties in Parkinson's disease.

BACKGROUND: Handwriting in Parkinson's disease (PD) features specific abnormalities which are difficult to assess in clinical practice since no specific tool for evaluation of spontaneous movement is currently available. OBJECTIVE: This study aims to validate the 'Systematic Screening of Handwriting Difficulties' (SOS-test) in patients with PD. METHODS: Handwriting performance of 87 patients and 26 healthy age-matched controls was examined using the SOS-test. Sixty-seven patients were tested a second time within a period of one month. Participants were asked to copy as much as possible of a text within 5 minutes with the instruction to write as neatly and quickly as in daily life. Writing speed (letters in 5 minutes), size (mm) and quality of handwriting were compared. Correlation analysis was performed between SOS outcomes and other fine motor skill measurements and disease characteristics. Intrarater, interrater and test-retest reliability were assessed using the intraclass correlation coefficient (ICC) and Spearman correlation coefficient. RESULTS: Patients with PD had a smaller (p = 0.043) and slower (p<0.001) handwriting and showed worse writing quality (p = 0.031) compared to controls. The outcomes of the SOS-test significantly correlated with fine motor skill performance and disease duration and severity. Furthermore, the test showed excellent intrarater, interrater and test-retest reliability (ICC > 0.769 for both groups). CONCLUSION: The SOS-test is a short and effective tool to detect handwriting problems in PD with excellent reliability. It can therefore be recommended as a clinical instrument for standardized screening of handwriting deficits in PD.

Structural Brain Alterations in Motor Subtypes of Parkinson's Disease: Evidence from Probabilistic Tractography and Shape Analysis.

BACKGROUND AND OBJECTIVES: The postural instability and gait disorder (PIGD) and tremor dominant (TD) subtypes of Parkinson's disease (PD) show different patterns of alterations in functional connectivity (FC) between specific brain regions. This study aimed to investigate the relation between symptomatic heterogeneity in PD and structural alterations underlying these FC changes. METHODS: 68 PD patients classified as PIGD (n = 41) or TD (n = 19) and 19 age-matched controls underwent Magnetic Resonance Imaging (MRI). Diffusion-weighted images were used to assess fractional anisotropy (FA) and mean diffusivity (MD) at the whole-brain level using tract-based spatial statistics (TBSS). In addition, structural connectivity was assessed between regions that previously showed altered FC using probabilistic tractography. Anatomical images were used to determine shape and volume of the putamen, caudate and pallidum. RESULTS: TBSS revealed widespread FA reductions in PIGD compared to controls involving the superior longitudinal fasciculi and corpus callosum. No such differences were found in TD. Both PD subgroups had increased MD compared to controls in tracts connecting the left caudate with the bilateral ventral putamen. TD patients additionally showed increased MD compared to PIGD and controls in tracts connecting the right inferior parietal lobule with the right premotor and primary motor cortex, which previously showed altered FC. We also found grey matter atrophy in the rostrodorsal head of the caudate in PIGD compared to controls. CONCLUSION: Microstructural changes in white matter tracts, particularly in those connecting striatal sub-areas, partly underlie FC alterations in PD subtypes. Caudate shape alterations further implicate the striatum in PIGD pathophysiology.

Progression of postural control and gait deficits in Parkinson's disease and freezing of gait: A longitudinal study.

BACKGROUND AND AIMS: The relationship between impaired postural control and freezing of gait (FOG) in Parkinson's disease (PD) is still unclear. Our aim was to identify if postural control deficits and gait dysfunction progress differently in freezers compared to non-freezers and whether this relates to FOG development. METHODS: 76 PD patients, classified as freezer (n = 17) or non-freezer (n = 59), and 24 controls underwent a gait and postural control assessments at baseline and after 12 months follow-up. Non-freezers who developed FOG during the study period were categorized as FOG converters (n = 5). Gait was analyzed during walking at self-preferred pace. Postural control was assessed using the Mini-BESTest and its sub-categories: sensory orientation, anticipatory, reactive and dynamic postural control. RESULTS: Mini-BESTest scores were lower in PD compared to controls (p < 0.001), and in freezers compared to non-freezers (p = 0.02). PD has worse anticipatory (p = 0.01), reactive (p = 0.02) and dynamic postural control (p = 0.003) compared to controls. Freezers scored lower on dynamic postural control compared to non-freezers (p = 0.02). There were no baseline differences between converters and non-converters. Decline in postural control was worse in PD compared to controls (p = 0.02) as shown by a greater decrease in the total Mini-BESTest score. Similar patterns were found in freezers (p = 0.006), who also showed more decline in anticipatory (p < 0.001) and dynamic postural control (p = 0.02) compared to non-freezers. FOG converters had a greater decline in the total Mini-BESTest (p = 0.005) and dynamic postural control scores (p = 0.04) compared to non-converters. Gait outcomes showed no significant differences in any of the analyses. CONCLUSION: FOG is associated with more severe decline in postural control, which can be detected by the clinical Mini-BESTest.