Cognitive and Motor Aspects of Parkinson's Disease Associated with Dysphagia

Exploring the Neuropsychological Correlates of Swallowing Disorders in People with Parkinson's Disease: a Cross-Sectional Study

Around 80% of persons with Parkinson's disease (PD) present symptoms of dysphagia. Although cognitive impairment may contribute to dysphagia, few studies have investigated the association between the PD neuropsychological profile and objective measures of swallowing dysfunction. Since the swallowing function comprises involuntary but also voluntary actions, we hypothesize that specific measures of attention and executive functions can be underlined in PD-related dysphagia. Therefore, the aim of this study was to extensively investigate the correlation and the relationship between attentive and executive functions and safety/efficiency of pharyngeal phase of swallowing in people with PD. All participants received a fiberoptic endoscopic evaluation of swallowing and were evaluated using the Penetration Aspiration Scale (PAS); the Yale Pharyngeal Residue Severity Rating Scale (IT-YPRSRS), and the Functional Oral Intake Scale (FOIS-IT). Participants also underwent a neuropsychological assessment covering global cognitive status, attention, and frontal executive functions. Correlations and associations between neuropsychological measures and swallowing components were calculated. Twenty-one participants with PD (mean age 69.38 ± 6.58 years, mean disease duration 8.38 ± 5.31 years; mean MDS-UPDRS III 43.95 ± 24.18) completed all evaluations. The most significant correlations were found between attentive functions (i.e., Stroop Time), and executive functions (i.e., Raven's Progressive Matrices, Digit Backward and Semantic Fluency), and FOIS-IT, PAS, and IT-YPRSRS sinuses and valleculae. These associations were not influenced by disease duration. These results suggest that a dysfunction to attentional processes and/or to executive functions can contribute to penetration and the presence of pharyngeal residue in participants with middle-stage PD.

Self-Reported Voice and Swallow Questionnaires' Alignment with Unified Parkinson's Disease Rating Scale Questions: A Preliminary Study

PURPOSE

The purpose of this manuscript was twofold: to investigate how clinical voice and swallow questionnaires align with self-reports from speech/voice and swallow domains of the Unified Parkinson's Disease Rating Scale (UPDRS), and how decline in self-reported speech/voice measures predict decline in self-reported swallowing measures.

METHODS

This observational, preliminary cross-sectional study included 15 people diagnosed with Idiopathic Parkinson's Disease. Participants completed the Voice Related Quality of Life (V-RQOL), Sydney Swallow Questionnaire (SSQ), and cognitive screening (Montreal Cognitive Assessment; MoCA) to account for cognitive impairment during self-reported speech/voice and swallow measures. They also completed the speech/voice and swallow components of the UPDRS.

RESULTS

There were significant associations between the SSQ and UPDRS question 2.3 (chewing/swallowing) (P < 0.001), but not between UPDRS question 2.1 (speech/voice) and V-RQOL. However, the MoCA was significantly and directionally associated with V-RQOL scores (P = 0.01). Finally, the V-RQOL was significantly associated with SSQ scores in a multiple regression model (P = 0.02).

CONCLUSIONS

Speech/voice and swallow-related questions from the UPDRS may be viable initial screening tools to facilitate faster and earlier laryngeal function testing. Substantially more research should be undertaken to assess how well these UPDRS question domains are indicative of underlying speech/voice or swallow dysfunction.

Management and Treatment for Dysphagia in Neurodegenerative Disorders

Patients with neurodegenerative disorders (NDDs) often experience functional dysphagia, which may involve dysfunction in a specific phase of swallowing or in the entire process. This review outlines the approach to dysphagia in the setting of NDDs. Distinguishing the etiology of dysphagia can be difficult, and it is important to always look out for signs pointing to NDD as the cause. Thorough diagnostic work-up is essential, and it includes a comprehensive history and physical examination, alongside swallowing function tests, such as fiberoptic endoscopic evaluation of swallowing, videofluoroscopic swallowing study, and high-resolution manometry. Management requires a multidisciplinary approach with a treatment plan tailored to each patient. This involves dietary guidance, swallowing rehabilitation, and surgery in cases in which improvement with rehabilitation is inadequate. Surgery may involve altering certain pharyngolaryngeal structures to facilitate swallowing and reduce the risk of aspiration (swallowing improvement surgery) or separating the airway and digestive tract while sacrificing laryngeal function, with the main goal of preventing aspiration (aspiration prevention surgery). Proper management stems from recognizing the impact of these disorders on swallowing and consistently finding ways to improve the quality of life of patients.

Relationship between Post-Stroke Cognitive Impairment and Severe Dysphagia: A Retrospective Cohort Study

Objective: To investigate the relationship between post-stroke cognitive impairment (PSCI) and severe post-stroke dysphagia (PSD) and explore the risk factors related to PSCI combined with severe PSD. Methods: Data from patients were collated from the rehabilitation-specific disease database. The Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), Videofluoroscopy Swallowing Study (VFSS), Penetration-aspiration Scale (PAS), and Functional Oral Intake Scale (FOIS) were used to evaluate cognitive and swallowing functions. Differences between groups were determined by the Pearson chi-square test (χ2) or Fisher exact test. PAS and FOIS data were analyzed with the use of the Wilcoxon rank-sum or Kruskal−Wallis test in the prespecified subgroup analysis. Risk factors were investigated by multivariate logistic regression. Results: A total of 1555 patients were identified with PSCI. The results indicated that patients with PSCI had a higher incidence rate of severe PSD as compared to patients without PSCI (p < 0.001). Patients with severe PSCI were more likely to clinically manifest oral phase dysfunction (p = 0.024), while mild PSCI patients mainly manifested pharyngeal phase dysfunction (p < 0.001). There was a significant difference in FOIS score changes between subgroups during the hospitalization period (severe PSCI vs. moderate PSCI and severe PSCI vs. mild PSCI) (all p < 0.001). In addition, multivariate logistic regression revealed pneumonia (p < 0.001), tracheotomy (p < 0.001), and dysarthria (p = 0.006) were related to PSCI, combined with severe PSD. Conclusion: PSCI may be related to severe PSD. Patients with severe PSCI were more likely to manifest oral phase dysfunction, while mild PSCI manifested pharyngeal phase dysfunction. Pneumonia, tracheotomy, and dysarthria were risk factors related to PSCI combined with severe PSD.

Six-Year Follow-Up of Dysphagia in Patients with Parkinson's Disease

The current study sought to examine longitudinal changes of dysphagia in Parkinson's disease, identify predictors of dysphagia aggravation and elucidate the influence of dysphagia on other symptoms in Parkinson's disease patients. Forty-eight patients with Parkinson's disease were enrolled. All patients underwent videofluoroscopic study of swallowing evaluation and a battery of neuropsychological assessments at baseline in 2014 and at follow-up in 2020. We used t-tests or Wilcoxon tests for comparative analysis between patients with/without dysphagia and comparative analysis of longitudinal data. We used Spearman's correlation analysis to examine predictors of dysphagia aggravation, and the Wilcoxon test to compare neuropsychological aggravation between patients with/without dysphagia at baseline. Swallowing function, cognitive function, depression, anxiety, and quality of life were aggravated at follow-up. Dysphagia prevalence increased from 27.08 at baseline to 39.58% at follow-up. Spearman's correlation results showed that dysphagia was more likely to become aggravated in male patients compared with female patients (P = 0.0049). Cognitive impairment at baseline was significantly related to dysphagia aggravation (P = 0.042). Patients with dysphagia at baseline exhibited a significantly greater increase in anxiety scores than patients without dysphagia at baseline (P = 0.021). The results revealed that male sex and cognitive impairment predicted worsening dysphagia in Parkinson's disease patients, and suggested that dysphagia may have a negative impact on anxiety in Parkinson's disease patients. The results highlight the importance of swallowing function screening and necessary instrumental checks, such as videofluoroscopic study of swallowing, in Parkinson's disease patients.

Impact of Progression of Parkinson's Disease on Swallowing Ability and Oral Environment

This study investigated the impact of the severity and treatment of Parkinson's disease (PD) on the swallowing ability and oral environment of patients. Swallowing dysfunction increases the aspiration risk and may lead to poor oral health among patients with PD. We investigated the influences of PD progression and drug treatment on the swallowing ability and oral environment using simple noninvasive screening measurements. We recruited 87 patients with PD (mean age, 71.9 ± 8.0 years; mean Hoehn and Yahr score, 2.9 ± 0.9). The PD condition was assessed in each patient using the unified Parkinson's disease rating scale (UPDRS) part III, diet type and oropharyngeal function using the swallowing disturbances questionnaire (SDQ), maximum bite force (MBF), tongue pressure (TP), and oral bacterial count (OBC). Levodopa equivalent daily dose (LEDD) was also calculated for 56 participants. Based on an SDQ score of ≥11, 29.5% of patients were dysphagic, but almost all were still on a regular diet. The SDQ score was positively correlated with disease duration (rho = 0.228, p=0.047) and UPDRS part III score (rho = 0.307, p=0.007) but was negatively correlated with OBC (rho = -0.289, p=0.012). OBC was significantly higher among patients with an SDQ score of <11 (nondysphagic) (p=0.01), and the SDQ score was lower in patients with higher OBC requiring professional oral care (p=0.03). However, OBC was also negatively correlated with LEDD (rho = -0.411, p=0.004). These results indicated low self-awareness of dysphagia among the participants and an association between dysphagia and PD progression. Moreover, the oral environment could have deteriorated with swallowing dysfunction. Patients and clinicians should be aware that higher LEDD can increase xerostomia and associated deficits in oral health.

Comparison of Patient-Reported and Caregiver-Reported Swallowing-Related Quality of Life in Parkinson's Disease

This pilot study explored agreement on swallowing-related quality-of-life scores reported by individuals with Parkinson's disease (PD) and their caregivers. Thirty-six patient-caregiver pairs completed the Swallowing Quality of Life Questionnaire (SWAL-QOL) using an online survey format. Additional background and clinical information was ascertained. A Wilcoxon signed-rank test was completed to compare the means of scores between individuals with PD and caregivers. Factors potentially influencing SWAL-QOL scores (age, employment status, sex, ethnicity, race, previous history of swallowing evaluation or treatment, caregiver concern about patient cognition, caregiver burden, and time since onset of disease) were explored using Spearman Coefficient Correlation tests. The Holm-Bonferroni method was used to adjust for multiple comparisons. Results did not reveal significant differences in SWAL-QOL scores between individuals with PD and caregiver pairs. There was a moderate degree of reliability and agreement between paired patient and caregiver scores, with the average ICC measures being 0.598 (95% CI [358, 0.748]) (F(71, 72) = 2.451, p < 0.0001). After adjusting for multiple comparisons, caregiver burden was found to be the only significant factor associated with caregivers' reported scores. No significant influential factor on reported scores by individuals with PD was found. These pilot results suggest individuals with PD and their caregivers may report similar swallowing-related quality-of-life scores. Further, caregiver burden appears to be an influential factor for caregiver-reported scores. Future studies should investigate the clinical benefits of including caregiver SWAL-QOL ratings in assessments, either as a supplement to patient scores to identify discrepancies across the dyad or in place of patient scores if needed. Further, caregiver burden and its influence on dysphagia identification and management should be explored, with targeted interventions to manage caregiver burden.

Effect of cognitive and motor dual-task on oropharyngeal swallowing in Parkinson's disease

BACKGROUND

Dysphagia frequently occurs in patients with Parkinson's disease (PD) and is associated with severe complications. However, the underlying pathology is poorly understood at present. This study investigated the effect of cognitive and motor dual-task interference on oropharyngeal swallowing in PD.

METHODS

Thirty PD patients (23 men, mean age 65.90 ± 9.32 years, mean Hoehn and Yahr stage 2.62 ± 0.81, mean UPDRS 18.00 ± 7.18) were examined using flexible endoscopic evaluation of swallowing (FEES). FEES was performed during three paradigms: at baseline without interference, during a cognitive dual-task, and during a motor dual-task. Oropharyngeal swallowing function was rated using a score which was validated to detect changes in PD related dysphagia. The three paradigms were compared using a two-way-repetitive-measures-ANOVA and a post-hoc-analysis.

RESULTS

Mean swallowing score in baseline FEES was 10.67 ± 5.89. It significantly increased (worsened) to 15.97 ± 7.62 (p < 0.001) in the motor dual-task and to 14.55 ± 7.49 (p < 0.001) in the cognitive dual-task. Premature bolus spillage and pharyngeal residue both significantly increased during both of the dual-task conditions whereas penetration/aspiration events did not change.

CONCLUSION

Oropharyngeal swallowing in patients with PD is not purely reflexive but requires mental capacity. Additional allocation of attentional resources in the central control of swallowing seems to be an effective compensatory mechanism in PD-related dysphagia: The proposed dual-task protocol may be useful to challenge swallowing functional reserve. Conversely, as a therapeutic strategy, it could be beneficial to focus attention on swallowing and to avoid dual-task situations.

Effects of cognitive and motor dual-tasks on oropharyngeal swallowing assessed with FEES in healthy individuals

Dysphagia is frequent in many neurological diseases and gives rise to severe complications such as malnutrition, dehydration and aspiration pneumonia. Therefore, early detection and management of dysphagia is essential and can reduce mortality. This study investigated the effect of cognitive and motor dual-task interference on swallowing in healthy participants, as dual-task effects are reported for other motor tasks such as gait and speech. 27 participants (17 females; 29.2 ± 4.1 years) were included in this prospective study and examined using flexible endoscopic evaluation of swallowing (FEES). Using a previously established FEES-based score, the paradigms "baseline swallowing", "cognitive dual-task" and "motor dual-task" were assessed. Scores of the three paradigms were compared using a repetitive measures ANOVA and post-hoc analysis. Mean baseline swallowing score in single task was 5 ± 3. It worsened to 6 ± 5 in the cognitive (p = 0.118), and to 8 ± 5 in the motor dual-task condition (p < 0.001). This change was driven by subclinical worsening of premature bolus spillage and pharyngeal residue. Oropharyngeal swallowing is not exclusively reflexive in nature but requires attention, which leads to motor dual-task interference. This has potential diagnostic and therapeutic implications, e.g. in the early screening for dysphagia or in avoiding dual-task situations while eating.

A new swallowing supplement for dysphagia in patients with Parkinson's disease

Dysphagia associated with Parkinson's disease (PD) affects the mortality and quality of life of patients with PD. Avoiding aspiration and maintaining swallowing ability are among the concerns regarding PD care. Therefore, we developed a swallowing supplement for easier swallowing and tolerability in patients with PD. Thirty patients with PD and 50 healthy controls were enrolled and their swallowing function measured using the videofluoroscopic swallowing study (VFSS) and several dysphagia scales. The Unified Parkinson's Disease Rating Scale motor scores, Hoehn and Yahr stage, and levodopa doses were evaluated in patients with PD. The VFSS and survey were used to assess the viscosity, color, taste, nutrition, safety, and tolerability of the swallowing supplement. The MMSE score, serum albumin, and hemoglobin levels, and oral conditions were worse in the PD group than in the control group. Compared with controls, patients with PD had significantly lower total and sub-item scores of the swallowing quality of life (swal-QoL). Using commercialized yogurt, the pharyngeal delay time (PDT) and the modified penetration aspiration scale were higher in the PD group than in the control group. The swallowing supplement significantly shortened the PDT and pharyngeal transit time (PTT). Moreover, compared with commercialized yogurt, it improved pharyngeal wall coating, PTT, and aspiration in the videofluoroscopic dysphagia subscales. The survey scores were above average to good in the "easy swallowing" and "pharyngeal residual sense" items and tolerable in the remaining 6 preference items. This swallowing supplement could prevent aspiration and dysphagia complications in patients with PD.

Oro-Pharyngeal Dysphagia in Parkinson's Disease and Related Movement Disorders

Oro-pharyngeal dysphagia is a common symptom in patients with Parkinson’s disease (PD) and related disorders, even in their early stage of diseases. Dysphagia in these patients has been underdiagnosed, probably due to poor the self-awareness of the conditions and the underuse of validated tools and objective instruments for assessment. The early detection and intervention of dysphagia are closely related to improving the quality of life and decreasing the mortality rate in these patients. The purpose of this paper is to give an overview of the characteristics of dysphagia, including the epidemiology, pathophysiology, and clinical symptomatology, in patients with PD compared with other parkinsonian disorders and movement disorders. The management of dysphagia and future research directions related to these disorders are also discussed.

Dual Tasking Influences Cough Sensorimotor Outcomes in Healthy Young Adults

Purpose Reflex cough is an essential airway protective mechanism that often occurs in the context of divided attention. The effect of divided attention on measures of reflexive cough airflow and sensitivity remains unknown. We present findings from a study testing the effects of divided attention (via a dual-task paradigm) on measures of reflex cough in healthy young adults. Method Volunteers (N = 20, age = 20-40 years) underwent 4 blocks of capsaicin-induced cough challenges. Within each block, capsaicin ranging from 0 to 200 μM was presented in a randomized order. Two blocks consisted of cough testing only (single task). During the other 2 blocks, participants counted tones while simultaneously undergoing cough testing (dual task). Measures of cough motor response, self-reported urge-to-cough, cough frequency, and cough airflow were collected. Results Participants coughed more in the single-task condition compared to the dual-task condition (p ≤ .001). Participants' urge-to-cough ratings were lower in the dual-task condition (x̅ = 2, "slight") compared to the single-task condition (x̅ = 3, "moderate"; p = .007). Participants' cough reflex sensitivity thresholds were significantly increased in the dual-task condition (p = .002). Cough peak expiratory flow rates did not change between the 2 conditions (p = .34). Conclusions Somatosensation of tussive stimuli changes during dual tasking. Abnormal cortical resource allocation may be a mechanism involved in silent aspiration.

Evaluation of dysphagia in different phenotypes of early and idiopathic Parkinsonism

Background

Parkinsonism (PD) is a common neurodegenerative disorders into which dysphagia occurs mainly in the late stage and to a lesser extent in an early stage. Diagnosis of dysphagia particularly in early idiopathic Parkinson's disease (IPD) is important as dysphagia affects the quality of life of patients and most of the patients are unaware of this important symptom.

Method

Fifty-four patients were enrolled in this study presented with early IPD attending to the outpatient clinic of Sohag University Hospital. All PD patients were assessed by using Unified Parkinson's Disease Rating Scale (UPDRS) and modified Hoehn and Yahr scale. IPD patients were classified into tremor dominant (TD) and postural instability/gait disorder (PIGD) phenotypes. Swallowing disturbance questionnaire (SDQ) and fiberoptic endoscopic evaluation of swallowing (FEES) were used to evaluate dysphagia.

Results

Thirty-five percent of patients experienced dysphagia when the patients were questioned, and this percent rises to 40% on using FEES. The results of SDQ were significantly correlated to the results of more accurate FEES. The percentage of dysphagia was higher in patients with PIGD than TD phenotype. Dysphagia was significantly associated with the mean of the Mini-Mental State Examination (MMSE), UPDRS, and modified Hoehn and Yahr scale.

Conclusions

Dysphagia is a prevalent symptom in early IPD and significantly correlated with Parkinsonism phenotype, UPDRS, and modified Hoehn and Yahr scale.

Evidence of Oropharyngeal Dysfunction in Feeding in the Rat Rotenone Model of Parkinson's Disease

Swallowing disorders in Parkinson's disease are not responsive to dopamine depletion therapy and contribute to morbidity. They are poorly understood owing to a lack of adequate models. We present the first evidence of oropharyngeal changes in a rotenone toxicity model of Parkinson's disease. Rats were recorded while feeding before and after daily rotenone injections at two different doses (2.75 mg/kg and 3 mg/kg). The higher dose had a much more severe parkinsonian phenotype than the low dose. Timing and amplitude of chewing changed, as did the coordination of chewing and swallowing. Dose-dependent effects were evident. These preliminary results indicate that future research in toxicological models of Parkinson's disease should incorporate the study of oropharyngeal dysfunction. A better understanding of nongenetic models of Parkinson's disease in feeding may open new avenues for research into the neurological and behavioral bases for swallowing dysfunction in Parkinson's disease.

Relationship Between Cognitive Function and Dysphagia After Stroke

OBJECTIVE

To investigate the characteristics of cognitive deficits in patients with post-stroke dysphagia, and to analyze the relationships between cognitive dysfunction and severity of dysphagia in supratentorial stroke.

METHODS

A total of 55 patients with first-ever supratentorial lesion stroke were enrolled retrospectively, within 3 months of onset. We rated dysphagia from 0 (normal) to 4 (severe) using the dysphagia severity scale (DSS) through clinical examinations and videofluoroscopic swallowing studies (VFSS). The subjects were classified either as non-dysphagic (scale 0) or dysphagic (scale 1 to 4). We compared general characteristics, stroke severity and the functional scores of the two groups. We then performed comprehensive cognitive function tests and investigated the differences in cognitive performance between the two groups, and analyzed the correlation between cognitive test scores, DSS, and parameters of oral and pharyngeal phase.

RESULTS

Fugl-Meyer motor assessment, the Berg Balance Scale, and the Korean version of the Modified Barthel Index showed significant differences between the two groups. Cognitive test scores for the dysphagia group were significantly lower than the non-dysphagia group. Significant correlations were shown between dysphagia severity and certain cognitive subtest scores: visual span backward (p=0.039), trail making tests A (p=0.042) and B (p=0.002), and Raven progressive matrices (p=0.002). The presence of dysphagia was also significantly correlated with cognitive subtests, in particular for visual attention and executive attention (odds ratio [OR]=1.009; 95% confidence interval [CI], 1.002-1.016; p=0.017). Parameters of premature loss were also significantly correlated with the same subtests (OR=1.009; 95% CI, 1.002-1.016; p=0.017).

CONCLUSION

Our results suggest that cognitive function is associated with the presence and severity of post-stroke dysphagia. Above all, visual attention and executive functions may have meaningful influence on the oral phase of swallowing in stroke patients with supratentorial lesions.

Swallowing in Parkinson's disease: clinical issues and management

Changes to swallowing affect most people with Parkinson's disease (PD). Changes may not initially exercise a decisive impact, but can later pose significant threats to nutritional, hydration and respiratory health and psychosocial quality of life. This review, from a largely clinical viewpoint, outlines the nature of changes in PD and considers the issue of how many people are affected and in what ways. It outlines main approaches to assessment and management, with an emphasis on aspects relevant to PD. Dysphagia contributes to drooling in PD. The review therefore also touches on the nature and management of this condition that has its own set of health and psychosocial quality-of-life issues.

[Importance of the detection of dysphagia in geriatric patients]

INTRODUCTION

Oropharyngeal dysphagia is one of the lesser known geriatric syndromes, despite its enormous impact on functional capacity, quality of life, and health of those affected.

MATERIAL AND METHODS

A descriptive and prospective study was conducted by the Geriatric Department of Barbastro Hospital (Huesca), from March 2012 to October 2014, as biannual and annual reviews in October 2015. This study included all patients on whom a volume-viscosity clinical examination (MECV-V test) was performed to suspecting dysphagia.

RESULTS

The study included 266 patients with a mean age of 82.35±12.3 years, and with a mean Barthel index score of 20.5±25.4, and mean Charlson index of 1.77±1.6. The test was performed in 105 cases after stroke (40%), 53 in dementia (20%), 24 in Parkinsonism (9%), and for other different reasons in 80 (31%). Dysphagia was diagnosed in 228 (86%) cases. Enteral nutrition was given in 25 (10.9%) cases. The test results were shown in the discharge report in 45% of the tests with positive result. The mean survival obtained after test in the patients who died was 230.8±256.5 days. Differences in survival at 12 months were found in patients with positive test, without finding a clear relationship with functional status and comorbidity.

CONCLUSIONS

Dysphagia has a significant mortality, and the use of thickeners after its detection should be properly reported.

Gut dysfunction in Parkinson's disease

Early involvement of gut is observed in Parkinson’s disease (PD) and symptoms such as constipation may precede motor symptoms. α-Synuclein pathology is extensively evident in the gut and appears to follow a rostrocaudal gradient. The gut may act as the starting point of PD pathology with spread toward the central nervous system. This spread of the synuclein pathology raises the possibility of prion-like propagation in PD pathogenesis. Recently, the role of gut microbiota in PD pathogenesis has received attention and some phenotypic correlation has also been shown. The extensive involvement of the gut in PD even in its early stages has led to the evaluation of enteric α-synuclein as a possible biomarker of early PD. The clinical manifestations of gastrointestinal dysfunction in PD include malnutrition, oral and dental disorders, sialorrhea, dysphagia, gastroparesis, constipation, and defecatory dysfunction. These conditions are quite distressing for the patients and require relevant investigations and adequate management. Treatment usually involves both pharmacological and non-pharmacological measures. One important aspect of gut dysfunction is its contribution to the clinical fluctuations in PD. Dysphagia and gastroparesis lead to inadequate absorption of oral anti-PD medications. These lead to response fluctuations, particularly delayed-on and no-on, and there is significant relationship between levodopa pharmacokinetics and gastric emptying in patients with PD. Therefore, in such cases, alternative routes of administration or drug delivery systems may be required.