Fatigue and Its Associated Factors in Spinocerebellar Ataxia Type 3/Machado-Joseph Disease.

Fatigue has been described in several neurodegenerative diseases, reducing quality of life. A systematic evaluation of this clinical feature is lacking in SCA3/MJD. The aim of this study was to evaluate the frequency and the factors associated with fatigue in SCA3/MJD. Patients with SCA3/MJD and matched healthy controls answered the Modified Fatigue Impact Scale (MFIS), Beck Inventory Depression (BDI) and Epworth Sleepiness Scale (ESS). Scale for the assessment and rating of ataxia (SARA) was used to determine ataxia severity. We used Mann-Whitney and Fisher exact tests to compare mean scores and proportions between groups. Linear regression analyses were employed to investigate factors associated with fatigue in SCA3/MJD. Seventy-four patients were included with a mean age and disease duration of 47.2 ± 12.8 and 9.5 ± 6.37 years, respectively. There were 38 men and 36 women. Mean (CAG)n was 72.2 ± 3.8. Mean MFIS score was higher in patients with SCA3/MJD (41.4 ± 16.2 vs 18.4 ± 12.9, p < 0.001). According to BDI scores, relevant depressive symptoms were found in 69.4 % of patients but only in 10.4 % of controls (p < 0.001). The proportion of patients with ESS scores indicating excessive daytime somnolence was also higher than controls (37.5 vs 22.3 %, p = 0.05). In the multiple regression analysis, both BDI and ESS scores were associated with fatigue (r = 0.67, p < 0.001 and p = 0.01). Fatigue is frequent and strongly associated with depression and excessive daytime somnolence in SCA3/MJD.

Cerebellar Gray Matter Alterations in Huntington Disease: A Voxel-Based Morphometry Study.

Neuropathological and neuroimaging studies in Huntington disease (HD) have suggested a role for the cerebellum. Our goal was to perform a detailed evaluation of cerebellar morphology. We performed the Unified HD rating scale (UHDRS) and Montreal cognitive assessment (MOCA) in 26 HD patients and 26 healthy controls. We created a two-sample test to analyze cerebellar gray matter (GM) differences between groups and another to correlate GM alterations with UHDRS and MOCA, corrected for age, expanded cytosine-adenine-guanine repeats, and disease duration using the spatially unbiased atlas template (SUIT)-SPM-toolbox which preserves anatomical detailing. We found increased GM density in the anterior cerebellum compared to controls. Higher GM density in the postero-superior lobe correlated with mood symptoms. Worse motor function and better cognitive function correlated with GM changes in the posterior cerebellum (false discovery rate (FDR) correction p < 0.05 and k > 100 voxels). In this detailed study of the in vivo cerebellar morphology in HD, we observed GM changes in regions involved in sensorimotor integration, motor planning, and emotional processing, supporting cerebellar involvement in the neuropathological process of HD.

Differential Pattern of Cerebellar Atrophy in Tremor-Predominant and Akinetic/Rigidity-Predominant Parkinson's Disease.

Parkinson's disease (PD) is an akinetic-rigid disorder characterized by basal ganglia dysfunction and a possible cerebello-thalamo-cortical circuit involvement. This study aims to investigate the pattern of cerebellar involvement in PD and to assess whether it correlates with clinical parameters. MRI scans were acquired from 50 healthy controls (HC) and 63 patients; 44 were classified as tremor-predominant-PD (PDT) and 19 as akinetic/rigidity-predominant-PD (PDAR). We designed an analysis of covariance including the three groups and contrasted as follows: (1) all 63 PD vs HC, (2) PDT vs HC, (3) PDAR vs HC, and (4) PDT vs PDAR. For a precise evaluation of the cerebellum, we used the SUIT tool for voxel-based morphometry. Applying p = 0.001 and extent threshold = 20 voxels, the overall PD group vs HC showed decreased gray matter (GM) in the left lobules VI and crus I. The PDT group showed decreased cerebellar GM when compared with HC at left lobules VI, VIIb, and VIIIa; at right lobules Crus I, VIIb, and VIIIb; and vermal lobules VI and VIIIa. When compared with PDAR, PDT also showed a decrease in the left lobules VIIIa (p < 0.001). There were small clusters of both positive and negative correlation between disease duration and PDT group. The PDAR group showed no cerebellar changes. Our findings support the growing evidence of cerebellar involvement in the pathogenesis of the resting tremor.

Nonneurological Involvement in Late-Onset Friedreich Ataxia (LOFA): Exploring the Phenotypes.

Friedreich's ataxia (FDRA) is the most common inherited ataxia worldwide, caused by homozygous GAA expansions in the FXN gene. Patients usually have early onset ataxia, areflexia, Babinski sign, scoliosis and pes cavus, but at least 25 % of cases have atypical phenotypes. Disease begins after the age of 25 in occasional patients (late-onset Friedreich ataxia (LOFA)). Little is known about the frequency and clinical profile of LOFA patients. One hundred six patients with molecular confirmation of FDRA and followed in three Brazilian outpatient centers were enrolled. General demographics, GAA expansion size, age at onset, cardiac, endocrine, and skeletal manifestations were evaluated and compared between LOFA and classic FDRA (cFDRA) groups. We used Mann-Whitney and Fisher tests to compare means and proportions between groups; p values <0.05 were considered significant. LOFA accounted for 17 % (18/106) and cFDRA for 83 % (88/106) of the patients. There were 13 and 48 women in each group, respectively. LOFA patients were significantly older and had smaller GAA expansions. Clinically, LOFA group had a tendency toward lower frequency of diabetes/impaired glucose tolerance (5.8 vs. 17 %, p = 0.29) and cardiomyopathy (16.6 vs. 28.4 %, p = 0.38). Skeletal abnormalities were significantly less frequent in LOFA (scoliosis 22 vs. 61 %, p = 0.003, and pes cavus 22 vs.75 %, p < 0.001) as were spasticity and sustained reflexes, found in 22 % of LOFA patients but in none of the cFDRA patients (p = 0.001). LOFA accounts for 17 % of Brazilian FDRA patients evaluated herein. Clinically, orthopedic features and spasticity with retained reflexes are helpful tips to differentiate LOFA from cFDRA patients.

Nonmotor Symptoms in Parkinson's Disease.

Nonmotor symptoms (NMSs) in Parkinson's disease (PD) have become increasingly recognized as major determinants of quality of life across cultures worldwide. Behavioral symptoms include dementia, depression, anxiety, apathy, and fatigue. Somatic symptoms include hypotension, constipation, diaphoresis, and pain. However, somatic symptoms may also be intrinsic, such as dementia, and iatrogenic, such as compulsive disorders. The authors address some of the more common disorders, yet few have been the target of clinical trials.

Longitudinal magnetic resonance imaging study shows progressive pyramidal and callosal damage in Friedreich's ataxia.

INTRODUCTION: Spinal cord and peripheral nerves are classically known to be damaged in Friedreich's ataxia, but the extent of cerebral involvement in the disease and its progression over time are not yet characterized. The aim of this study was to evaluate longitudinally cerebral damage in Friedreich's ataxia. METHODS: We enrolled 31 patients and 40 controls, which were evaluated at baseline and after 1 and 2 years. To assess gray matter, we employed voxel-based morphometry and cortical thickness measurements. White matter was evaluated using diffusion tensor imaging. Statistical analyses were both cross-sectional and longitudinal (corrected for multiple comparisons). RESULTS: Group comparison between patients and controls revealed widespread macrostructural differences at baseline: gray matter atrophy in the dentate nuclei, brainstem, and precentral gyri; and white matter atrophy in the cerebellum and superior cerebellar peduncles, brainstem, and periventricular areas. We did not identify any longitudinal volumetric change over time. There were extensive microstructural alterations, including superior cerebellar peduncles, corpus callosum, and pyramidal tracts. Longitudinal analyses identified progressive microstructural abnormalities at the corpus callosum, pyramidal tracts, and superior cerebellar peduncles after 1 year of follow-up. CONCLUSION: Patients with Friedreich's ataxia present more widespread gray and white matter damage than previously reported, including not only infratentorial areas, but also supratentorial structures. Furthermore, patients with Friedreich's ataxia have progressive microstructural abnormalities amenable to detection in a short-term follow-up.

Spinal cord damage in Machado-Joseph disease.

Machado-Joseph disease (SCA3) is the most frequent spinocerebellar ataxia worldwide and characterized by remarkable phenotypic heterogeneity. MRI-based studies in SCA3 focused in the cerebellum and connections, but little is known about cord damage in the disease and its clinical relevance. To evaluate the spinal cord damage in SCA3 through quantitative analysis of MRI scans. A group of 48 patients with SCA3 and 48 age and gender-matched healthy controls underwent MRI on a 3T scanner. We used T1-weighted 3D images to estimate the cervical spinal cord area (CA) and eccentricity (CE) at three C2/C3 levels based on a semi-automatic image segmentation protocol. The scale for assessment and rating of ataxia (SARA) was employed to quantify disease severity. The two groups-SCA3 and controls-were significantly different regarding CA (49.5 ± 7.3 vs 67.2 ± 6.3 mm(2), p < 0.001) and CE values (0.79 ± 0.06 vs 0.75 ± 0.05, p = 0.005). In addition, CA presented a significant correlation with SARA scores in the patient group (p = 0.010). CE was not associated with SARA scores (p = 0.857). In the multiple variable regression, we found that disease duration was the only variable associated with CA (coefficient = -0.629, p = 0.025). SCA3 is characterized by cervical cord atrophy and antero-posterior flattening. In addition, the spinal cord areas did correlate with disease severity. This suggests that quantitative analyses of the spinal cord MRI might be a useful biomarker in SCA3.

Association of the Area Deprivation Index With Dementia Basic Workup and Diagnosis in Central and Western Virginia: A Cross-Sectional Study.

Background and Objectives: The Area Deprivation Index (ADI) provides a validated and multidimensional metric of areal disadvantage. Our goals were to determine if the ADI influences the likelihood of receiving workup based on published guidelines and an etiologic diagnosis of dementia in Central and Western Virginia. Methods: We collected deidentified data from the electronic health record of individuals aged 50-105 years diagnosed with dementia at the University of Virginia (UVA) Medical Center (2016-2021) and at Carillion Clinic (2018-2021). Visit-specific ICD-10 codes were used to classify each dementia diagnosis as "disease-specific" (e.g., Alzheimer disease) or "general" (e.g., unspecified dementia). Following the American Academy of Neurology guidelines, we considered the evaluation performed as "adequate" if patients had vitamin B12, thyroid-stimulating hormone, and brain CT or magnetic resonance imaging within 6 months of the initial diagnosis. Census tract ADI was linked to study participants using the unique census tract identifier derived from the participants' home addresses at the time of diagnosis. Statistical modeling occurred under a Bayesian paradigm implemented using a standard code in R. Results: The study included 13,431 individuals diagnosed with dementia at UVA (n = 7,152) and Carillion Clinic (n = 6,279). Of those, 32.5% and 20.4% received "disease-specific" diagnoses at UVA and Carillion Clinic and 8.2% and 20.4% underwent "adequate" workup, respectively. The adjusted relationship between census tract ADI and the likelihood of a disease-specific diagnosis was U-shaped: Residence in moderately disadvantaged areas was associated with the lowest likelihood of disease-specific diagnosis. Discussion: Most patients diagnosed with dementia did not receive an adequate evaluation or an etiologic diagnosis. Those living in locations just above the national median ADI levels had the lowest likelihood of receiving an etiologic diagnosis, lower than those in the least and most deprived areas. Renewed awareness efforts among providers are needed to increase compliance with diagnostic guidelines.

Nonmotor and extracerebellar features in Machado-Joseph disease: a review.

Spinocerebellar ataxia type 3 or Machado-Joseph disease is the most common spinocerebellar ataxia worldwide, and the high frequency of nonmotor manifestations in Machado-Joseph disease demonstrates how variable is the clinical expression of this single genetic entity. Anatomical, physiological, clinical, and functional neuroimaging data reinforce the idea of a degenerative process involving extracerebellar regions of the nervous system in Machado-Joseph disease. Brain imaging and neuropathologic studies have revealed atrophy of the pons, basal ganglia, midbrain, medulla oblongata, multiple cranial nerve nuclei, and thalamus and of the frontal, parietal, temporal, occipital, and limbic lobes. This review provides relevant information about nonmotor manifestations and extracerebellar symptoms in Machado-Joseph disease. The main nonmotor manifestations of Machado-Joseph disease described in previous data and discussed in this article are: sleep disorders, cognitive and affective disturbances, psychiatric symptoms, olfactory dysfunction, peripheral neuropathy, pain, cramps, fatigue, nutritional problems, and dysautonomia. In addition, we conducted a brief discussion of noncerebellar motor manifestations, highlighting movement disorders. © 2013 Movement Disorder Society.

A multimodal evaluation of microstructural white matter damage in spinocerebellar ataxia type 3.

Although white matter damage may play a major role in the pathogenesis of spinocerebellar ataxia 3 (SCA3), available data rely exclusively upon macrostructural analyses. In this setting we designed a study to investigate white matter integrity. We evaluated 38 genetically-confirmed SCA3 patients (mean age, 52.76 ± 12.70 years; 21 males) with clinical scales and brain magnetic resonance imaging (MRI) and 38 healthy subjects as a control group (mean age, 48.86 ± 12.07 years, 20 male). All individuals underwent the same protocol for high-resolution T1 and T2 images and diffusion tensor imaging acquisition (32 directions) in a 3-T scanner. We used Tract-Based Spatial Statistics (FSL 4.1.4) to analyze diffusion data and SPM8/DARTEL for voxel-based morphometry of infratentorial structures. T2-relaxometry of cerebellum was performed with in-house-developed software Aftervoxel and Interactive Volume Segmentation (IVS). Patients' mean age at onset was 40.02 ± 11.48 years and mean duration of disease was 9.3 ± 2.7 years. Mean International Cooperative Ataxia Rating Scale (ICARS) and Scale for Assessment and Rating of Ataxia (SARA) scores were 32.08 ± 4.01 and 14.65 ± 7.33, respectively. Voxel-based morphometry demonstrated a volumetric reduction of gray and white matter in cerebellum and brainstem (P <.001). We found reduced fractional anisotropy (P <.05) in the cerebellum and brainstem. There were also areas of increased radial diffusivity (P <.05) in the cerebellum, brainstem, thalamus, frontal lobes, and temporal lobes. In addition, we found decreased T2-relaxation values in the white matter of the right cerebellar hemisphere. Microstructural white matter dysfunction, not previously reported, occurs in the cerebellum and brainstem of SCA3 patients.

Dysautonomia is frequent in Machado-Joseph disease: clinical and neurophysiological evaluation.

Autonomic dysfunction has been already described in patients with SCA3/MJD, but several important questions remain unanswered. The objectives of this study are to determine the frequency and the intensity of autonomic manifestations in SCA3/MJD, as well as to identify possible correlations between autonomic manifestations and genetic and clinical parameters. We have performed clinical and electrophysiological evaluations of 40 patients with SCA3/MJD and 38 healthy controls. We used the Scale for the Assessment and Rating of Ataxia (SARA) and the scales for Outcomes in Parkinson's Disease: Autonomic Questionnaire to quantify the severity of ataxia and autonomic complaints, respectively. We also studied heart rate variability at rest, during orthostatic challenge (30:15 ratio), Valsalva maneuver (Valsalva index), and deep breathing (E/I ratio). We evaluated spectral analyses of RR intervals at rest and the sympathetic skin response. Mean RR intervals at rest and the 30:15 ratio were different between patients and controls (811.8 versus 933.4 ms; p = 0.001 and 1.10 versus 1.15; p = 0.038, respectively). The Valsalva index and the E/I ratio were similar between the groups (p = 0.373 and p = 0.08). Spectral analysis presented distinct results in patients and controls, related to low- and high-frequency power (p < 0.001 and <0.001, respectively). We found cardiovascular and sympathetic sweat disautonomia in 30 % and 45 % of the patients with SCA3/MJD. Autonomic manifestations were related neither to genetic (CAG repeat length) nor clinical parameters (age, disease duration, SARA scores). Autonomic dysfunction is frequent and sometimes disabling in SCA3/MJD. We found evidence of both cardiovascular and sudomotor dysfunction in the disease.

Neuroanatomical correlates of depression in Friedreich's ataxia: a voxel-based morphometry study.

Affective disorders have been increasingly recognized in neurodegenerative diseases and often result in poor quality of life. However, the frequency, clinical relevance, and anatomical substrate of depression in Friedreich's ataxia were not yet evaluated. We assessed 22 patients with Friedreich's ataxia for major depression using Beck Depression Inventory and cerebral 3 T MRI scans. We then employed whole-brain voxel-based morphometry analyses on volumetric T1 datasets to compare tissue loss between patients with and without major depression. Patients (36.3 %) fulfilled criteria for major depression (8/22). Mean Beck Depression Inventory (BDI) score was 9.63 ± 8.95 and the depressive group had significantly higher score compared to non-depressive group (18.5 ± 8.6 vs 4.4 ± 2.9, p < 0.001). There was no correlation between Beck Depression Inventory score and age of patients, ataxia severity, age at onset, or duration of the disease. The comparison between patient groups found no significant differences of white matter volumes. In contrast, we found reduction of gray matter volumes in the depressive group in medial and orbital region of frontal lobe and anterior cingulate gyri (p < 0.001). Regression analyses have shown that BDI scores were inversely correlated with gray matter volume at right superior frontal gyrus. Major depression is frequent in Friedreich's ataxia and possibly under recognized. Our results strongly suggest that this may not be a simply reactive phenomenon, but rather associated to structural abnormalities.

Spinal cord atrophy correlates with disability in Friedreich's ataxia.

Although Friedreich's ataxia is characterized by spinal cord atrophy, it remains to be investigated the possible correlation of such atrophy with clinical disability and genetic parameters. Thirty-three patients with Friedreich's ataxia and 30 healthy controls underwent MRI on a 3 T scanner. We used T1-weighted 3D images to estimate spinal cord area and eccentricity at C2/C3 level based on a semi-automatic image segmentation protocol. We quantified severity of ataxia with the Friedreich ataxia rating scale (FARS). Mean cord area in Friedreich's ataxia was smaller than in controls (38 vs 67.9 mm(2), p < 0.001). In contrast, mean cord eccentricity was significantly higher in Friedreich's ataxia when compared to the controls (0.82 vs 0.76, p < 0.001). There was a significant correlation between cord areas and the FARS scores (r = -0.53, p = 0.002). Cord damage in Friedreich's ataxia results in atrophy combined with flattening. Cord area is associated to clinical disability and might be useful as a biomarker in the disease.

Primary Palliative Care in Huntington's Disease.

Background: Palliative care practices, including communication about patient-centered goals of care and advance care planning (ACP), have the potential to enhance care throughout the course of Huntington's disease (HD) and related disorders. The goal of our project was to develop a pilot program that integrates primary palliative care practices with interdisciplinary care for HD. Objectives: (1) To train HD team members to facilitate goals of care and ACP conversations at all stages of HD; (2) To create materials for care planning in HD focused on patient-centered goals of care and health-related quality of life; and (3) To modify clinic workflow to include goals of care and ACP discussions. Methods: We defined planning domains to expand care planning beyond end-of-life concerns. We created a patient and family guide to advance care planning in HD. We conducted VitalTalk communications training with the HD team. We modified the interdisciplinary clinic workflow to include ACP and developed an EMR template for documentation. Results: After communication training, more team members felt well prepared to discuss serious news (12.5% to 50%) and manage difficult conversations (25% to 62.5%). The proportion of clinic visits including advance care planning discussions increased from 12.5% to 30.6% during the pilot phase. Conclusions: Provision of primary palliative care for HD in an interdisciplinary clinic is feasible. Integration of palliative care practices into HD specialty care requires additional training and modification of clinic operations.

White and grey matter abnormalities in patients with SPG11 mutations.

BACKGROUND: Mutations in SPG11 are the most frequent known cause of autosomal recessive hereditary spastic paraplegia. Corpus callosum thinning is a hallmark of the condition but little is known about damage to other structures in the CNS. OBJECTIVE: To evaluate in vivo cerebral damage in patients with SPG11 mutations. METHODS: 5 patients and 15 age and sex matched healthy controls underwent high resolution diffusion tensor imaging (32 directions) and a T1 volumetric (1 mm slices) acquisition protocol in a 3 T scanner (Philips Achieva). These sequences were then analysed through voxel based morphometry (VBM) and tract based spatial statistics (TBSS). RESULTS: Mean age of the patients was 23.6±4.5 years (range 14-45) and mean duration of disease was 12 years (range 5-15). All patients presented with progressive spastic paraplegia and three were already wheelchair bound when first evaluated. Mutations found were: c.529_533delATATT, c.704_705delAT, c.733_734delAT, c.118C>T and c.7256A>G. VBM identified significant grey matter atrophy in both the thalamus and lentiform nuclei. TBSS analyses revealed reduced fractional anisotropy involving symmetrically subcortical white matter of the temporal and frontal lobes, the cingulated gyrus, cuneus, striatum, corpus callosum and brainstem. CONCLUSIONS: Widespread white matter damage in patients with SPG11 mutations has been demonstrated. Grey matter atrophy was prominent in both the thalamus and basal ganglia but not in the cerebral cortex. These findings suggest that neuronal damage/dysfunction is more widespread than previously recognised in this condition.

Volumetric brain changes in thalamus, corpus callosum and medial temporal structures: mild Alzheimer's disease compared with amnestic mild cognitive impairment.

BACKGROUND: It is widely known that atrophy of medial temporal structures is present in the mild stage of Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI). However, structures such as the thalamus and corpus callosum are much less studied. METHODS: We compared the volumes of the entorhinal cortex, hippocampus, thalamus and the corpus callosum in 14 controls, 14 patients with mild AD and 15 with aMCI and correlated these volumes with neuropsychological data. MRI was obtained at 2 T followed by manual segmentation. RESULTS: We found atrophy in hippocampi and thalami of MCI patients compared to controls, and in the bilateral entorhinal cortex of aMCI compared to AD patients. All the structures showed atrophy in AD patients compared to controls, including the corpus callosum. CONCLUSIONS: Our study confirms that thalamic areas are atrophied in aMCI, and the corpus callosum might represent a good structural marker for mild AD. Those areas were associated with cognitive functions already described in the literature.

Paroxysmal Hypothermia With Prominent Parkinsonian Features After Suprachiasmatic Tumor Resection.

Paroxysmal hypothermia (PH) is a rare syndrome of stereotyped episodes of hypothermia, bradycardia, and altered mental status occurring in patients with hypothalamic lesions. Prior cases have mentioned bradykinesia, ataxia, and dysarthria, but parkinsonism has not been described as a specific feature of PH. We report two patients, an adult and a child, who developed PH after suprachiasmatic tumor resection, both with clinical presentations notable for prominent parkinsonian features despite no evidence of parkinsonism during the intervening months and years. We propose a diagnostic algorithm and scoring tool to aid in the clinical diagnosis of PH presenting as parkinsonism.

Practical Considerations in the Administration of Aducanumab for the Neurologist.

Aducanumab (Aduhelm), developed by the biotechnology firm Biogen in Cambridge, MA, was approved using the less common accelerated approval pathway by the Federal Drug Administration (FDA) reserved for treatments that fill a significant unmet need.1 Its approval on June 7, 2021, has been met with an outpouring of opinions from prescribers, insurers, advocacy groups, and hospital systems regarding its risk-benefit profile.2-4 Originally approved for all forms of Alzheimer disease (AD), the FDA updated aducanumab's labeling on July 8, 2021, for "treatment in patients with mild cognitive impairment (MCI) or mild dementia stage of disease, the population in which treatment was initiated in clinical trials."5 With 6 million people nationally in the United States who suffer from AD and an anticipated one-third of those who may now fulfill the criteria under the revised labeling, the implications of aducanumab's approval continue to generate national interest.6.

Multi-Dimensional, Short-Timescale Quantification of Parkinson's Disease and Essential Tremor Motor Dysfunction.

Introduction: Parkinson's disease (PD) is a progressive movement disorder characterized by heterogenous motor dysfunction with fluctuations in severity. Objective, short-timescale characterization of this dysfunction is necessary as therapies become increasingly adaptive. Objectives: This study aims to characterize a novel, naturalistic, and goal-directed tablet-based task and complementary analysis protocol designed to characterize the motor features of PD. Methods: A total of 26 patients with PD and without deep brain stimulation (DBS), 20 control subjects, and eight patients with PD and with DBS completed the task. Eight metrics, each designed to capture an aspect of motor dysfunction in PD, were calculated from 1-second, non-overlapping epochs of the raw positional and pressure data captured during task completion. These metrics were used to generate a classifier using a support vector machine (SVM) model to produce a unifying, scalar "motor error score" (MES). The data generated from these patients with PD were compared to same-day standard clinical assessments. Additionally, these data were compared to analogous data generated from a separate group of 12 patients with essential tremor (ET) to assess the task's specificity for different movement disorders. Finally, an SVM model was generated for each of the eight patients with PD and with DBS to differentiate between their motor dysfunction in the "DBS On" and "DBS Off" stimulation states. Results: The eight metrics calculated from the raw positional and force data captured during task completion were non-redundant. MES generated by the SVM analysis protocol showed a strong correlation with MDS-UPDRS-III scores assigned by movement disorder specialists. Analysis of the relative contributions of each of the eight metrics showed a significant difference between the motor dysfunction of PD and ET. Much of this difference was attributable to the homogenous, tremor-dominant phenotype of ET motor dysfunction. Finally, in individual patients with PD with DBS, task performance and subsequent SVM classification effectively differentiated between the "DBS On" and "DBS Off" stimulation states. Conclusion: This tablet-based task and analysis protocol correlated strongly with expert clinical assessments of PD motor dysfunction. Additionally, the task showed specificity for PD when compared to ET, another common movement disorder. This specificity was driven by the relative heterogeneity of motor dysfunction of PD compared to ET. Finally, the task was able to distinguish between the "DBS On" and "DBS Off" states within single patients with PD. This task provides temporally-precise and specific information about motor dysfunction in at least two movement disorders that could feasibly correlate to neural activity.