Cognitive impairment in REM-sleep behaviour disorder and individuals at risk of Parkinson's disease.

BACKGROUND: Mild cognitive impairment (MCI) is commonly present at the time of Parkinson's Disease (PD) diagnosis, but its prevalence amongst individuals at increased risk of PD is unclear. METHODS: Cognition was assessed using the Montreal Cognitive Assessment (MoCA) in 208 participants in the PREDICT-PD study, and 25 participants with REM-sleep behaviour disorder (RBD). Prevalence of MCI level I was determined in all participants, and level II MCI in the RBD sub-group. RESULTS: Total MoCA scores were worse in the higher risk than the lower risk group defined as those below the 15th percentile of risk (p = 0.009), and in the RBD group compared to all healthy participants (p < 0.001). The prevalence of MCI level I was 12.8% in the lower-risk, 21.9% in the higher-risk (within the highest 15th percentile) and 64% in RBD participants; 66% of RBD participants had MCI level II with multi-domain MCI, but particularly attention and memory deficits. CONCLUSIONS: Cognitive impairment is increased in different groups at higher risk of PD, particularly in the subgroup formally diagnosed with RBD.

Antidepressants Trial in Parkinson's Disease (ADepT-PD): protocol for a randomised placebo-controlled trial on the effectiveness of escitalopram and nortriptyline on depressive symptoms in Parkinson's disease.

BACKGROUND: Depressive symptoms are common in patients with Parkinson's disease and depression is a significant predictor of functional impairment, reduced quality of life and general well-being in Parkinson's disease. Despite the high prevalence of depression, evidence on the effectiveness and tolerability of antidepressants in this population is limited. The primary aim of this trial is to establish the clinical and cost effectiveness of escitalopram and nortriptyline for the treatment of depression in Parkinson's disease. METHODS: This is a multi-centre, double-blind, randomised placebo-controlled trial in 408 people with Parkinson's disease with subsyndromal depression, major depressive disorder or persistent depressive disorder and a Beck Depression Inventory-II (BDI-II) score of 14 or above. Participants will be randomised into one of three groups, receiving either escitalopram, nortriptyline or placebo for 12 months. Trial participation is face-to-face, hybrid or remote. The primary outcome measure is the BDI-II score following 8 weeks of treatment. Secondary outcomes will be collected at baseline, 8, 26 and 52 weeks and following withdrawal, including severity of anxiety and depression scores as well as Parkinson's disease motor severity, and ratings of non-motor symptoms, cognitive function, health-related quality of life, levodopa-equivalence dose, changes in medication, overall clinical effectiveness, capability, health and social care resource use, carer health-related quality of life, adverse effects and number of dropouts. DISCUSSION: This trial aims to determine the effectiveness of escitalopram and nortriptyline for reducing depressive symptoms in Parkinson's disease over 8 weeks, to provide information on the effect of these medications on anxiety and other non-motor symptoms in PD and on impact on patients and caregivers, and to examine their effect on change in motor severity. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT03652870 Date of registration - 29th August 2018.

The motor prodromes of parkinson's disease: from bedside observation to large-scale application.

There is sufficient evidence that the pathological process that causes Parkinson's disease begins years before the clinical diagnosis is made. Over the last 15 years, there has been much interest in the existence of a prodrome in some patients, with a particular focus on non-motor symptoms such as reduced sense of smell, REM-sleep disorder, depression, and constipation. Given that the diagnostic criteria for Parkinson's disease depends on the presence of bradykinesia, it is somewhat surprising that there has been much less research into the possibility of subtle motor dysfunction as a pre-diagnostic pointer. This review will focus on early motor features and provide some advice on how to detect and measure them.

Experiences of advance care planning in Parkinson's disease and atypical parkinsonian disorders: a mixed methods systematic review.

BACKGROUND AND PURPOSE: Advance care planning allows people to plan for their future care needs and can include medical, psychological and social aspects. However, little is known on the use, experience of and attitudes towards advance care planning in patients with parkinsonian disorders, their family carers and healthcare professionals. METHODS: A systematic search of online databases was conducted in April 2019 using a narrative synthesis approach with thematic analysis and tabulation to synthesize the findings. RESULTS: In all, 507 articles were identified and 27 were included. There were five overarching themes: (i) what is involved in advance care planning discussions, (ii) when and how advance care planning discussions are initiated, (iii) barriers to advance care planning, (iv) the role of healthcare professionals and (v) the role of the family carer. This evidence was used to highlight eight effective components to support optimal advance care planning in parkinsonian disorders: advance care planning discussions should be individualized in content, timing and approach; patients should be invited to discuss advance care planning early and regularly; palliative care services should be introduced early; a skilled professional should deliver advance care planning; support to family carers should be offered in the advance care planning process; healthcare professionals should be educated on parkinsonian disorders and palliative care; advance care planning should be clearly documented and shared with relevant services; and healthcare professionals should be enabled to conduct effective advance care planning. CONCLUSIONS: These components can inform best practice in advance care planning in patients with parkinsonian disorders.

The late stage of Parkinson's -results of a large multinational study on motor and non-motor complications.

INTRODUCTION: There is little information on the late stages of parkinsonism. METHODS: We conducted a multicentre study in 692 patients with late stage parkinsonism in six European countries. Inclusion criteria were disease duration of ≥7 years and either Hoehn and Yahr stage ≥4 or Schwab and England score of 50 or less. RESULTS: Average disease duration was 15.4 (SD 7.7) years and mean total UPDRS score was 82.7 (SD 22.4). Dementia according to MDS-criteria was present in 37% of patients. Mean levodopa equivalence dose was 874.1 (SD 591.1) mg/d. Eighty two percent of patients reported falls, related to freezing (16%) or unrelated to freezing (21% of patients) or occurring both related and unrelated to freezing (45%), and were frequent in 26%. Moderate-severe difficulties were reported for turning in bed by 51%, speech by 43%, swallowing by 16% and tremor by 11%. Off-periods occurred in 68% and were present at least 50% of the day in 13%, with morning dystonia occurring in 35%. Dyskinesias were reported by 45% but were moderate or severe only in 7%. Moderate-severe fatigue, constipation, urinary symptoms and nocturia, concentration and memory problems were encountered by more than half of participants. Hallucinations (44%) or delusions (25%) were present in 63% and were moderate-severe in 15%. The association with overall disability was strongest for severity of falls/postural instability, bradykinesia, cognitive score and speech impairment. CONCLUSION: These data suggest that current treatment of late stage parkinsonism in the community remains insufficiently effective to alleviate disabling symptoms in many patients.

Impulse control and related behaviors in Parkinson's disease with dementia.

BACKGROUND AND PURPOSE: The objective was to determine the frequency, demographic and clinical correlates [such as age, sex, Parkinson's disease (PD) severity and dopaminergic treatment] of impulse control disorder (ICD) symptoms and related behaviors in patients with PD with (PD-D) and without (PD-ND) dementia. METHODS: We analyzed historical data from a national, multi-center, cross-sectional database and assessed ICDs and related behaviors with the Scale for Evaluation of Neuropsychiatric Disorders in Parkinson's Disease administered as a semi-structured interview to patients with PD-D (n = 85) and PD-ND (n = 444) and their informants. RESULTS: Dopamine agonist therapy use was common and similar in the two groups (78.8% in PD-D vs. 82.9% in PD-ND), but ICDs (23.5% vs. 13.3%, P = 0.02), hobbyism-punding (32.9% vs. 10.6%, P < 0.001) and dopaminergic medication abuse (8.2% vs. 3.2%, P = 0.03) were more common in the PD-D group. CONCLUSIONS: The finding that ICDs and related behaviors are more common in patients with PD frequently treated with dopamine agonists who also have comorbid dementia suggests that the neural substrates associated with PD dementia may also predispose to development of compulsive behaviors.

Heterogeneity in progression of prodromal features in Parkinson's disease.

BACKGROUND: In the pre-diagnostic phase of Parkinson's disease (PD), a range of motor and non-motor symptoms can occur. However, there is considerable variability in their onset and currently little information exists on the pattern of progression of clinical features before diagnosis. METHODS: We analysed data from a survey amongst patients with PD from 11 European countries by the European Parkinson's Disease Association. They completed questions on first occurrence of 21 pre-diagnostic features. A principal component analysis (PCA) with varimax rotation was performed to determine the co-occurrence of these features. FINDINGS: 1467 patients were included. Changes in movement were the most commonly reported features up to 4 years before diagnosis. However, at five or more years before diagnosis loss of sense of smell, sleep problems, fatigue and other non-motor features had been experienced most frequently. PCA of pre-diagnostic features' duration revealed three factors with eigenvalues over Kaiser's criterion of 1: a) a neuropsychiatric factor comprised of anxiety, depression, apathy, stress, and sleep problems; b) an axial factor defined by difficulty eating and/or swallowing problems, freezing, and falls/balance problems; and c) a motor factor with additional non-motor features. Bladder/bowel problems and tremor had low factor loadings on all components. However, in those with disease duration less than 5 years the autonomic features were associated with the axial factor and tremor loaded on both the motor and psychiatric symptom factors. INTERPRETATION: The identified symptom complexes in the pre-diagnostic stage of PD may be reflective of a shared pattern of pathological disease progression.

Experience of care for Parkinson's disease in European countries: a survey by the European Parkinson's Disease Association.

BACKGROUND: Few studies report on the experience of care for patients with Parkinson's disease (PD) from their own point of view. METHODS: An analysis was carried out of a survey in 11 European countries on self-reported access to services and satisfaction with different aspects of care. RESULTS: In all, 1775 people with PD (PwP) participated with disease duration ranging from <1 to 42 years. When referred to a specialist most were seen within 3 months but medication reviews occurred every 3 months in only 10%, every 6 months in 37%, once a year in 40% and every 2 years or less frequently in 13%. Waiting times to therapists were usually ≥4 months. Satisfaction with care was highest for involvement of PwP in decisions (63% of respondents satisfied) and involvement of family/carer (62%) followed by communication with PwP (57%), information received (54%), frequency of treatment reviews (52%) and suitability of treatment for the individual condition and circumstances (52%), but lowest for availability and accessibility of treatment when needed (48%) and collaborations between healthcare professionals in delivering care (41% satisfied). The main factors associated with overall satisfaction scores with care were the overall satisfaction with initial consultation (r = 0.26, P < 0.0001), the sensitivity with which the diagnosis was communicated, the quantity of information provided (both r = 0.24, P < 0.0001) and the frequency of medication review (r = 0.17, P < 0.0001). CONCLUSION: More coordinated and responsive care, tailored to the individual, with regular and timely medication reviews and information provision, is likely to improve satisfaction with care in current healthcare pathways.

Patient experiences of receiving a diagnosis of Parkinson's disease.

OBJECTIVE: To report patients' own experiences of receiving a diagnosis of Parkinson's disease (PD) and to identify factors influencing this experience. METHODS: A survey by the European Parkinson's Disease Association in 11 European countries. RESULTS: 1775 patients with an average age of 69.7 years participated of whom 54% were male. Those living in rural areas reported having waited longer to seek medical help (p < 0.05). A possible diagnosis of PD was made at the first appointment in a third of respondents. When the diagnosis was made, only 50% reported that the diagnosis was communicated sensitively. 38% of patients reported having been given enough time to ask questions and discuss concerns, but 29% did not. 98% of participants reported having been given information about PD at the time of diagnosis but 36% did not find the information given helpful. Patient satisfaction with the diagnostic consultation was positively associated with more sensitive delivery of diagnosis, the helpfulness and quantity of the information provided and time to ask questions (all p < 0.001). Where diagnosis was given by a specialist, participants reported greater perceived satisfaction with the diagnostic consultation, greater sensitivity of communicating the diagnosis, time to ask questions, provision and helpfulness of information, and earlier medication prescription (all p < 0.0001). CONCLUSIONS: There is a need to improve how the diagnosis of PD is communicated to patients, the opportunity to ask questions soon after diagnosis, and the amount, timing and quality of life information provided, as this is associated with greater satisfaction with the diagnostic process.

[MSA-QoL: disease-specific questionnaire to assess health-related quality of life in multiple system atrophy: validation of the German translation]. / MSA-QoL: spezifisches Bewertungsinstrument zur Erfassung der Lebensqualität bei Multisystematrophie : Validierung der deutschsprachigen Übersetzung.

BACKGROUND: Multiple system atrophy (MSA) is a rapidly progressive neurodegenerative disorder which causes early sustained disability and quality of life impairment. Recently, a self-reported questionnaire focusing on MSA-specific symptoms (Multiple System Atrophy Quality of Life questionnaire, MSA-QoL) was developed in the English language. This article reports the validation of the German translation of the MSA-QoL. METHODS: Translation of the MSA-QoL was implemented in a 3-tiered approach including a forward translation, a back translation and an independent review. For the validation study 38 consecutive patients with MSA according to the consensus criteria were recruited by the participating centers in a German-Austrian cohort. Data were analyzed using standard psychometric procedures. RESULTS: As determined by the independent review, the German translation of the MSA-QoL was classified as fully equivalent to the English version. The validation study confirmed good psychometric properties of the rating scale. CONCLUSION: The German translation of the MSA-QoL was shown to be a reliable patient-reported rating scale to determine health-related quality of life in MSA patients.

EFNS/MDS-ES/ENS [corrected] recommendations for the diagnosis of Parkinson's disease.

BACKGROUND: A Task Force was convened by the EFNS/MDS-ES Scientist Panel on Parkinson's disease (PD) and other movement disorders to systemically review relevant publications on the diagnosis of PD. METHODS: Following the EFNS instruction for the preparation of neurological diagnostic guidelines, recommendation levels have been generated for diagnostic criteria and investigations. RESULTS: For the clinical diagnosis, we recommend the use of the Queen Square Brain Bank criteria (Level B). Genetic testing for specific mutations is recommended on an individual basis (Level B), taking into account specific features (i.e. family history and age of onset). We recommend olfactory testing to differentiate PD from other parkinsonian disorders including recessive forms (Level A). Screening for pre-motor PD with olfactory testing requires additional tests due to limited specificity. Drug challenge tests are not recommended for the diagnosis in de novo parkinsonian patients. There is an insufficient evidence to support their role in the differential diagnosis between PD and other parkinsonian syndromes. We recommend an assessment of cognition and a screening for REM sleep behaviour disorder, psychotic manifestations and severe depression in the initial evaluation of suspected PD cases (Level A). Transcranial sonography is recommended for the differentiation of PD from atypical and secondary parkinsonian disorders (Level A), for the early diagnosis of PD and in the detection of subjects at risk for PD (Level A), although the technique is so far not universally used and requires some expertise. Because specificity of TCS for the development of PD is limited, TCS should be used in conjunction with other screening tests. Conventional magnetic resonance imaging and diffusion-weighted imaging at 1.5 T are recommended as neuroimaging tools that can support a diagnosis of multiple system atrophy (MSA) or progressive supranuclear palsy versus PD on the basis of regional atrophy and signal change as well as diffusivity patterns (Level A). DaTscan SPECT is registered in Europe and the United States for the differential diagnosis between degenerative parkinsonisms and essential tremor (Level A). More specifically, DaTscan is indicated in the presence of significant diagnostic uncertainty such as parkinsonism associated with neuroleptic exposure and atypical tremor manifestations such as isolated unilateral postural tremor. Studies of [(123) I]MIBG/SPECT cardiac uptake may be used to identify patients with PD versus controls and MSA patients (Level A). All other SPECT imaging studies do not fulfil registration standards and cannot be recommended for routine clinical use. At the moment, no conclusion can be drawn as to diagnostic efficacy of autonomic function tests, neurophysiological tests and positron emission tomography imaging in PD. CONCLUSIONS: The diagnosis of PD is still largely based on the correct identification of its clinical features. Selected investigations (genetic, olfactory, and neuroimaging studies) have an ancillary role in confirming the diagnosis, and some of them could be possibly used in the near future to identify subjects in a pre-symptomatic phase of the disease.

Validation of the French version of the MSA health-related Quality of Life scale (MSA-QoL).

INTRODUCTION: Multiple system atrophy (MSA) has considerable impact on health-related quality of life. The MSA health-related Quality of Life scale (MSA-QoL) is a patient-reported questionnaire, which has been recently designed to evaluate the quality of life in MSA. The objective of the present study was to validate the French version of the MSA-QoL questionnaire. METHODS: One hundred and thirty-six consecutive MSA patients were included in the study. Four patients with more than 10% missing responses were excluded from the final analysis. Data quality, scaling assumptions, acceptability, reliability and validity were assessed similar to the original validation of the English version. RESULTS: Missing responses were low, item and subscale scores were evenly distributed and floor and ceiling effects were negligible. Item-total correlations were higher than the recommended greater than 0.30 and internal consistency was high for all subscales. Test-retest reliability was good for all subscales. Validity was supported by moderate interscale correlations between the subscales and the predicted correlations with other scales assessing motor disability, activities of daily living, quality of life and mood. DISCUSSION: The French version of the MSA-QoL displays robust psychometric properties similar to the English version. CONCLUSION: The French version of MSA-QoL seems suitable for assessing quality of life in French speaking MSA patients.

Streptococcal infection, Tourette syndrome, and OCD: is there a connection?

BACKGROUND: A causal relationship of common streptococcal infections and childhood neuropsychiatric disorders has been postulated. OBJECTIVE: To test the hypothesis of an increased rate of streptococcal infections preceding the onset of neuropsychiatric disorders. METHODS: Case-control study of a large primary care database comparing the rate of possible streptococcal infections in patients aged 2-25 years with obsessive-compulsive disorder (OCD), Tourette syndrome (TS), and tics with that in controls matched for age, gender, and practice (20 per case). We also examined the influence of sociodemographic factors. RESULTS: There was no overall increased risk of prior possible streptococcal infection in patients with a diagnosis of OCD, TS, or tics. Subgroup analysis showed that patients with OCD had a slightly higher risk than controls of having had possible streptococcal infections without prescription of antibiotics in the 2 years prior to the onset of OCD (odds ratio 2.59, 95% confidence interval 1.18, 5.69; p = 0.02). Cases with TS or tics were not more likely to come from more affluent or urban areas, but more cases lived in areas with a greater proportion of white population (p value for trend = 0.05). CONCLUSIONS: The present study does not support a strong relationship between streptococcal infections and neuropsychiatric syndromes such as obsessive-compulsive disorder and Tourette syndrome. However, it is possible that a weak association (or a stronger association in a small susceptible subpopulation) was not detected due to nondifferential misclassification of exposure and limited statistical power. The data are consistent with previous reports of greater rates of diagnosis of Tourette syndrome or tics in white populations.

The prognosis of fixed dystonia: a follow-up study.

BACKGROUND: The syndrome of fixed dystonia includes both CRPS-dystonia and psychogenic dystonia. The underlying mechanisms are unclear, but a high prevalence of neuropsychiatric illness has previously been reported. METHODS: Clinical and neuropsychiatric follow-up study by telephone and self-administered instruments (HADS, SDQ-20, DES II, EQ-5D), on 41 patients with fixed dystonia after a mean of 7.6 (+/-3.6) years. RESULTS: We obtained information on clinical outcome in 35 (85.4%) patients and neuropsychiatric questionnaire data in 22 (53.7%). Eighty-three percent were women. Thirty-one percent had worsened, 46% were the same and 23% had improved, of whom 6% had major remissions. At follow-up, mean duration of illness was 11.8 (+/-4.9) years and mean age 43.2 (+/-14.8) years. Except for 1 patient who was re-diagnosed with corticobasal degeneration, the diagnosis remained unchanged in others. Forty-one percent had scores indicating anxiety and 18% indicating depression; 18% scored within the range of dissociative/somatoform disorders on DES II and 19% on SDQ-20. The mean EQ-5D index and VAS scores were 0.34 and 56.1%. Comparison between the 3 outcome groups revealed significant difference only in the EQ-5D (p=0.003). Only baseline CRPS predicted a worse outcome (chi(2)=0.006). CONCLUSIONS: Our findings revealed that the prognosis of this syndrome is poor, with improvement in less than 25% of patients, major remission in only 6% and continued worsening in a third. A high rate of neuropsychiatric findings was noted and new neuropsychiatric features had occurred in some. Average health status was poor. Of the baseline parameters, only CRPS predicted poorer outcome.

The Gilles de la Tourette syndrome-quality of life scale (GTS-QOL): development and validation.

BACKGROUND: Gilles de la Tourette syndrome (GTS) is a chronic neuropsychiatric disorder which has a significant detrimental impact on the health-related quality of life (HR-QOL) of patients. However, no patient-reported HR-QOL measures have been developed for this population. OBJECTIVE: The development and validation of a new scale for the quantitative assessment of HR-QOL in patients with GTS. METHODS: In stage 1 (item generation), a pool of 40 potential scale items was generated based on interviews with 133 GTS outpatients, literature review, and consultation with experts. In stage 2 (scale development), these items were administered to a sample of 192 GTS outpatients. Standard statistical methods were used to develop a rating scale satisfying criteria for acceptability, reliability, and validity. In stage 3 (scale evaluation), the psychometric properties of the resulting scale were tested in a second sample of 136 subjects recruited through the UK-Tourette Syndrome Association. RESULTS: Response data analysis and item reduction methods led to a final 27-item GTS-specific HR-QOL scale (GTS-QOL) with four subscales (psychological, physical, obsessional, and cognitive). The GTS-QOL demonstrated satisfactory scaling assumptions and acceptability; both internal consistency reliability and test-retest reliability were high (Cronbach alpha > or =0.8 and intraclass correlation coefficient > or =0.8); validity was supported by interscale correlations (range 0.5-0.7), confirmatory factor analysis, and correlation patterns with other rating scales and clinical variables. CONCLUSIONS: The Gilles de la Tourette syndrome (GTS)-specific health-related quality of life (HR-QOL) scale (GTS-QOL) is proposed as a new disease-specific patient-reported scale for the measurement of HR-QOL in patients with GTS, taking into account the complexity of the clinical picture of GTS.

Fourteen-year final report of the randomized PDRG-UK trial comparing three initial treatments in PD.

BACKGROUND: Ten-year follow-up results from the Parkinson's Disease Research Group of the United Kingdom trial demonstrated that there were no long-term advantages to initiating treatment with bromocriptine compared with l-dopa in early Parkinson disease (PD). Increased mortality in patients on selegiline combined with l-dopa led to premature termination of this arm after 6 years. METHODS: Between 1985 and 1990, 782 patients were recruited into an open pragmatic multicenter trial and were randomized to l-dopa/decarboxylase inhibitor (DDCI), l-dopa/DDCI plus selegiline, or bromocriptine. The main endpoints were mortality, disability, and motor complications. For final follow-up, health-related quality of life and mental function were also assessed. RESULTS: Median duration of follow-up at final assessment was 14 years in the 166 (21%) surviving participants who could be contacted. After adjustment for baseline characteristics, disability scores were better in the l-dopa than in the bromocriptine arm (Webster: 16.6 vs 19.8; p = 0.03; Northwestern University Disability: 34.3 vs 30.0, p = 0.05). Physical functioning (difference 20.8; 95% CI 10.0, 31.6; p < 0.001) and physical summary scores (difference 5.2; 95% CI 0.7, 9.7; p = 0.03) on the 36-item short-form health survey were also superior on l-dopa. Differences in mortality rates and prevalence of dyskinesias, motor fluctuations, and dementia were not significantly different. CONCLUSION: Initial treatment with the dopamine agonist bromocriptine did not reduce mortality or motor disability and the initially reduced frequency in motor complications was not sustained. We found no evidence of a long-term benefit or clinically relevant disease-modifying effect with initial dopamine agonist treatment.

Are patients with somatization disorder highly suggestible?

OBJECTIVE: High suggestibility is widely regarded as an important feature of patients with medically unexplained symptoms (MUS), particularly those with multiple MUS [i.e. somatization disorder (SD)], although there are few empirical data attesting to this assumption. A study was therefore conducted to compare levels of non-hypnotic suggestibility in patients with SD and medical controls. METHOD: A modified version of the Barber Suggestibility Scale was administered to 19 patients with SD and 17 controls with an established organic dystonia. RESULTS: Patients with SD were no more suggestible than control patients. Dystonia controls were more likely to deliberately comply with suggestions than the SD patients. CONCLUSION: Contrary to popular belief, high suggestibility is not necessarily a feature of SD.

Quantifying the impact of dyskinesias in PD: the PDYS-26: a patient-based outcome measure.

BACKGROUND: Drug-induced dyskinesias are a common and disabling clinical problem in the long-term management of Parkinson disease (PD). Their management and the development of new treatments rely on rigorous and meaningful dyskinesia measurement. Although clinician-based approaches exist, patient-based measures are limited. METHOD: Potential rating scale items concerning daily activities affected by dyskinesias were generated from patients, literature review, and expert opinion. The resulting 42-item questionnaire was administered to 98 patients known to have problematic dyskinesias; 72 patients were invited to complete it twice for test-retest reliability (trt). Rasch analysis guided scale development. Results were cross-validated using traditional psychometric methods by examining scaling assumptions (item means and variances, item-total correlations), reliability (Cronbach alpha, trt), and validity (factor analysis). External validation was performed against standard dyskinesia measures: blinded video rating using modified Goetz and Abnormal Involuntary Movements Scales (AIMS), and Unified PD Rating Scale (UPDRS) questions 32-34. RESULTS: Response rates were high. Fourteen items were removed because of high missing data. The remaining items were Rasch analyzed. Two items were removed because of misfit. The resulting 26 items formed a clinically and statistically conformable set. Traditional psychometric criteria were satisfied and external validation showed good correlation with the UPDRS items and moderate to good correlation with objective dyskinesia measures. CONCLUSION: The 26-item Parkinson Disease Dyskinesia Scale (PDYS-26) satisfied multiple criteria for reliable and valid measurement. Correlations with objective measures suggest that it captures related but not identical constructs. As a patient-derived scale that generates linear measurements, it could complement existing clinician-based dyskinesia measures.