Neuropathy as a potential complication of levodopa use in Parkinson's disease

The presence and potential etiologies of peripheral neuropathy (PN) in patients with Parkinson's Disease (PD) is unknown. We examined for presence of PN in patients with PD. From a PD patient population of 500 patients screened for features of symptomatic PN, patients were further selected for clinical, electrophysiological, and laboratory studies related to PN. This PD patient population with idiopathic PN (PD‐IPN) was compared to a group of PD patients without PN (PD‐only), and a large group of patients without PD with idiopathic PN (IPN) for abnormalities in Cbl, fasting homocysteine (Hcy), and fasting methylmalonic acid (MMA) levels. PD‐IPN and IPN patients identified with abnormalities in Cbl, Hcy, or MMA levels were treated with intramuscular Cbl for 1 to 2 years. Of 49 PD patients with symptomatic PN, 34 patients (69%) had PD‐IPN, and 32/34 (94%) had abnormal Hcy or MMA levels as compared to 26/258 (10%) of IPN patients. Cumulative lifetime L ‐dopa dosage and fasting MMA levels were associated with PN severity. Cbl therapy led to improvements in Hcy and MMA levels in all groups, and PN in PD‐IPN patients stabilized during therapy. PN in PD patients may be associated with iatrogenic Cbl metabolic abnormalities. Alternatively PN may be a peripheral nervous system manifestation of PD. © 2008 Movement Disorder Society     

Unmasking levodopa resistance in Parkinson's disease

Some motor and nonmotor features associated with Parkinson's disease (PD) do not seem to respond well to levodopa (or other forms of dopaminergic medication) or appear to become resistant to levodopa treatment with disease progression and longer disease duration. In this narrative review, we elaborate on this issue of levodopa resistance in PD. First, we discuss the possibility of pseudoresistance, which refers to dopamine‐sensitive symptoms or signs that falsely appear to be (or have become) resistant to levodopa, when in fact other mechanisms are at play, resulting in suboptimal dopaminergic efficacy. Examples include interindividual differences in pharmacodynamics and pharmacokinetics and underdosing because of dose‐limiting side effects or because of levodopa phobia. Moreover, pseudoresistance can emerge as not all features of PD respond adequately to the same dosage of levodopa. Second, we address that for several motor features (eg, freezing of gait or tremor) and several nonmotor features (eg, specific cognitive functions), the response to levodopa is fairly complex, with a combination of levodopa‐responsive, levodopa‐resistant, and even levodopa‐induced characteristics. A possible explanation relates to the mixed presence of underlying dopaminergic and nondopaminergic brain lesions. We suggest that clinicians take these possibilities into account before concluding that symptoms or signs of PD are totally levodopa resistant. © 2016 International Parkinson and Movement Disorder Society     

Evidence for small fiber neuropathy in early Parkinson's disease

IntroductionParkinson's disease (PD) is neurodegenerative movement disorder affecting primarily the central nervous system with several recognized non-motor symptoms that can occur at various stages of the disease. Recently it has been shown that patients with PD may be prone to peripheral nervous system pathology in the form of a peripheral neuropathy (PN). It is unclear if PN is an inherent feature of PD or if it is an iatrogenic effect of the mainstay PD treatment Levodopa.MethodsTo determine if peripheral neuropathy occurs in early untreated PD we employed a case-control study design using gold standard tests for PN, including neurological examination according to the Utah Early Neuropathy Scale (UENS) and nerve conduction studies, as well as new, more sensitive and informative tests for PN including the skin biopsy and corneal confocal microscopy (CCM).ResultsWe studied 26 patients with PD and 22 controls using the neurological examination and nerve conduction studies (NCS) and found no significant difference between groups except for some reduced vibration sense in the PD group. Epidermal nerve densities in the skin biopsies were similar between our cohorts. However, using CCM – a more sensitive test and a surrogate marker of small fiber damage in PN, we found that patients with PD had significantly reduced corneal nerve fiber densities and lengths as compared to controls.ConclusionsWe conclude that our positive CCM results provide evidence of preclinical PN in newly diagnosed PD patients.     

Longitudinal study of the motor response to levodopa in Parkinson's disease.

In this prospective study of 34 patients with Parkinson's disease, measurements of the short duration levodopa motor response have been performed in defined off states at 3 yearly intervals over a mean period of 11.4 years from the point of commencement of levodopa treatment. Twenty-two patients were still available for study; 10 had died and 2 were lost to follow-up. The levodopa motor response amplitude increases over the first 5 years of treatment, and thereafter, on and off scores worsen in parallel with conservation of the response. Patients who developed motor fluctuations within the first 5 years of treatment had, on average, a stronger response to levodopa with significantly better on phase motor function (P = 0.003). Although the proportion of "midline" motor disability (affecting gait, balance, and cranial motor function) increases with time, these deficits do not actually become unresponsive to levodopa. Patients who developed dementia had a significantly more rapid decline in motor function. The latest graph of serial scores for the whole cohort shows an upward curving or exponential increase in motor disability after the first decade of treatment. Applying a notional untreated disability line to this graph--an estimate of the disability that would have accrued if drugs had never been given--we suggest that the long-duration response to levodopa eventually runs down with disease progression.     

Intrajejunal levodopa infusion in Parkinson's disease: A pilot multicenter study of effects on nonmotor symptoms and quality of life

Switching from oral medications to continuous infusion of levodopa/carbidopa gel reduces motor complications in advanced Parkinson's disease (PD), but effects on nonmotor symptoms (NMSs) are unknown. In this prospective open‐label observational study, we report the effects of intrajejunal levodopa/carbidopa gel infusion on NMS in PD based on standard assessments utilizing the nonmotor symptoms scale (NMSS) along with the unified Parkinson's disease rating scale (UPDRS 3 motor and 4 complications) and quality of life (QoL) using the Parkinson's disease questionnaire (PDQ‐8). Twenty‐two advanced PD patients (mean age 58.6 years, duration of disease 15.3 years) were followed for 6 months. A statistically significant beneficial effect was shown in six of the nine domains of the NMSS: cardiovascular, sleep/fatigue, attention/memory, gastrointestinal, urinary, and miscellaneous (including pain and dribbling) and for the total score of this scale (NMSST) paralleling improvement of motor symptoms (UPDRS 3 motor and 4 complications in “best on” state) and dyskinesias/motor fluctuations. In addition, significant improvements were found using the Parkinson's disease sleep scale (PDSS) and the PDQ‐8 (QoL). The improvement in PDQ‐8 scores correlated highly significantly with the changes in NMSST, whereas a moderately strong correlation was observed with UPDRS changes. This is the first demonstration that a levodopa‐based continuous dopaminergic stimulation is beneficial for NMS and health‐related quality of life in PD in addition to the reduction of motor fluctuations and dyskinesias. © 2009 Movement Disorder Society     

Cognitive profile of Parkinson's disease patients: a comparative study between early-onset and late-onset Parkinson's disease

Aim: To investigate the influence of onset age on the occurrence and progression of cognitive dysfunction using neuropsychological tests and the electrophysiological component P300 in both early-onset Parkinson's disease (EOPD) and late-onset Parkinson's disease (LOPD) patients. Methods: A cohort of 76 EOPD patients and 166 LOPD patients was recruited for this study. Demographic information and clinical features, including age, disease duration, education level, family history, the Unified Parkinson's Disease Rating Scale, the Hoehn and Yahr stage, and depression scores were documented for each patient. The Mini-Mental State Examination, Montreal Cognitive Assessment (MoCA), Wechsler Adult Intelligence Scale – Revised, Chinese version (WAIS-RC) and Wechsler Memory Scale – Revised, Chinese version (WMS-RC) were used. In addition, P300 was also examined to assess cognitive function. Results: Although EOPD patients had longer disease duration, their cognitive dysfunction progressed more slowly. The MoCA tests revealed that EOPD patients had higher scores in visuospatial function, attention, delayed recall, and orientation than the LOPD patients. The difference between the two groups on the WMS-RC test did not reach significance, whereas the scores in executive function, visuospatial function and attention as measured on the WAIS-RC test were significantly lower in the LOPD group. In addition, P300 latencies were markedly delayed and P300 amplitudes were reduced in the LOPD group. Conclusions: The current findings demonstrated that cognitive dysfunction progressed more slowly in the EOPD group. Although the LOPD patients exhibited shorter disease durations, their cognitive abilities, including executive function, visuospatial function and attention, may have been impaired.     

Response of non-motor symptoms to levodopa in late-stage Parkinson's disease: Results of a levodopa challenge test

BackgroundNon-motor symptoms (NMS) are extremely common among late-stage Parkinson's disease (LSPD) patients. Levodopa (L-dopa) responsiveness seems to decrease with disease progression but its effect on NMS in LSPD still needs to be investigated.ObjectiveTo assess the response of blood pressure (BP), pain, fatigue and anxiety to L-dopa in LSPD patients.Methods20 LSPD patients, defined as Schwab and England ADL Scale <50 or Hoehn Yahr Stage >3 (MED ON) and 22 PD patients treated with subthalamic deep brain stimulation (advanced PD group) underwent an L-dopa challenge. BP and orthostatic hypotension (OH) assessment, a visual analogue scale (VAS) for pain and fatigue and the Strait Trait Anxiety (STAI) were evaluated before and after the L-dopa challenge.ResultsSystolic BP dropped significantly after L-dopa intake (p < 0.05) in LSPD patients, while there was no change in pain, fatigue or anxiety. L-dopa significantly improved (p < 0.05) pain and anxiety in the advanced PD group, whereas it had no effect on BP or fatigue. L-dopa-related adverse effects (AEs), namely OH and sleepiness, were more common among LSPD patients. 40% and 65% of LSPD patients were not able to fill out the VAS and the STAI, respectively, while measurement of orthostatic BP was not possible in four LSPD patients.ConclusionsThis exploratory study concludes that some non-motor variables in LSPD do not benefit from the acute action of L-dopa while it can still induce disabling AEs. There is a need for assessment tools of NMS adapted to these disabled LSPD patients.     

Longitudinal study of levodopa in Parkinson's disease: Effects of the advanced disease phase

Thirty‐four patients have been studied from the time of initiation of pharmacological treatment in a long‐term prospective study of levodopa effects and disease progression in Parkinson's disease. Objective motor scoring of the response to levodopa in defined off states was performed every 3 years. The mean time from the initiation of levodopa treatment to the most recent measurements was 18.2 years. Of 8 patients who are still alive, only 3 had none of the features of the advanced disease phase (dementia, hallucinations, frequent falling). Off‐phase motor function worsened at a yearly rate of 1.9% of the maximum disability score, although the plots of the serial scores showed that the magnitude of the levodopa response is well preserved. There was little difference in the rate of progression between patients with tremor‐dominant and non‐tremor‐dominant motor subtypes. Those who developed dementia had more rapid deterioration of motor scores, with significantly worse off‐phase (P = .008) and on‐phase (P = .03) motor function. A graph of serial scores of patients who have died, aligned for time of death, showed an upward curving trend of motor disability in the last 5 years of the disease course. Its advanced phase may reveal that Parkinson's disease has an exponential pattern of progression. © 2013 Movement Disorder Society     

Pattern of subclinical pulmonary dysfunctions in Parkinson's disease and the effect of levodopa.

We performed a detailed evaluation of pulmonary function in 53 patients with idiopathic Parkinson's disease (PD) who did not have symptoms of pulmonary or cardiac dysfunction. There was a significant pulmonary dysfunction of restrictive type which partially responded to levodopa. Compared to men, women were more severely affected. Pulmonary function assessment is recommended in PD, irrespective of severity of disease.     

Acute effects of immediate and controlled-release levodopa on mood in Parkinson's disease: A double-blind study.

Mood fluctuations related to levodopa (LD) dosing are well-known psychiatric complications of Parkinson's disease (PD). No formal studies explored how affective response to LD relates to the type of motor response to oral LD (stable or wearing-off) and to different pharmacokinetic profiles of oral LD. We used an intrasubject randomized double-blind crossover design to study 14 patients (7 stable, 7 wearing-off) who were monitored for motor status, mood, anxiety, and plasma LD levels 1 hour before and 6 hours after an oral dose of immediate-release (IR) and controlled-release LD formulations. Analysis of the dose-response curves showed a significant interaction between the type of motor response and the type of LD. Only the wearing-off patients had a significant mood elevation, and this effect was only significant following challenge with IR LD. Motor status strongly correlated with LD plasma levels and anxiety but not with mood ratings. Mood changes in PD patients are related to the patient's type of motor response to oral LD and also to the kinetic profile of the LD formulation used for dopaminergic replacement.     

Homocysteine levels after acute levodopa intake in patients with Parkinson's disease

Levodopa (L ‐dopa) administered with a dopadecarboxylase inhibitor (DDI) increases homocysteine plasma levels. This may support the onset of atherosclerosis‐related disorders and neuropsychiatric complications in patients with Parkinson's disease (PD). This homocysteine elevation is considered as long‐term effect of chronic L ‐dopa/DDI treatment. Little is known about the acute effects of L ‐dopa/DDI intake on homocysteine generation. The objective of this trial was to investigate the relations between L ‐dopa and homocysteine after acute L ‐dopa/DDI administration in PD patients with different L ‐dopa metabolism. Thirty PD patients were divided into groups with superior (I) and less (II) L ‐dopa absorption after standardized intake of 125 mg L ‐dopa/benserazide with determination of L ‐dopa, 3‐O‐methyl‐dopa (3‐OMD) and homocysteine in plasma at baseline, 30, 60, and 90 minutes. There was a homocysteine increase in Group I (F = 5; P = 0.005) and a moderate decrease in Group II (F = 4.27; P = 0.01). A rise of 3‐OMD (F = 10.51; P < 0.0001) appeared in Group I, but not in Group II (F = 0.91; P = 0.44), accordingly L ‐dopa accumulation was better in Group I than in Group II. Thus, in conclusion, L ‐dopa metabolism is an important component for homocysteine elevation after one time L ‐dopa/DDI administration in PD patients. © 2009 Movement Disorder Society     

Test-retest reliability of the unified Parkinson's disease rating scale in patients with early Parkinson's disease: results from a multicenter clinical trial.

Our objective was to assess the test-retest reliability of the Unified Parkinson's Disease Rating Scale (UPDRS). The UPDRS is the most widely used instrument for measuring severity of parkinsonian symptoms in clinical research and in practice. The validity and inter-rater reliability of this scale have been previously studied. We examined the test-retest (intrarater) reliability of the UPDRS and derived subscales. Four hundred patients with early-stage Parkinson's disease (PD) who were participating in a multicenter clinical trial were evaluated using the UPDRS on two separate occasions (screening and baseline visits) prior to receiving treatment. The same neurologist at each center rated the subjects at both examinations that were, on average, 14.6 +/- 7.6 days apart (range 3-36 days). Test-retest reliability was estimated using the intraclass correlation coefficient (ICC) for the total UPDRS score, the mental, ADL, and motor subscale scores, and other derived subscale scores. Weighted kappa statistics were calculated for individual UPDRS items. The ICCs for the UPDRS scores were as follows: total score, 0.92; mental, 0.74; ADL, 0.85; motor, 0.90. ICCs for derived symptom-based scales ranged from 0.69-0.88. Reliability of specific items was generally lower than for summary scales. Reliability was slightly better in patients for whom the testing interval was within 14 days. Based on conventional standards, the UPDRS scores were found to have excellent test-retest reliability in this sample of patients with early PD rated by academic movement disorder specialists. The findings are in agreement with previous reports on interrater reliability.     

Impairments of speed and amplitude of movement in Parkinson's disease: A pilot study

Bradykinesia, characterized by slowness and decreased amplitude of movement, is often considered the most important deficit in Parkinson's disease (PD). The current clinical rating of bradykinesia in PD, based on the motor subscale of the Unified Parkinson's disease Rating Scale (UPDRS‐III), does not individually weigh the impairments in speed and amplitude of rapid alternating movements. We sought to categorize movement in PD to determine whether speed and amplitude have different relationships to current measures of motor impairment and disability. Categories of speed and amplitude (normal, slow/low, and very‐slow/very‐low) were ascertained using an electromagnetic tracking device. Amplitude was disproportionally more affected than speed in the “off” state. UPDRS‐III and the Schwab & England disability scale were worst in patients with very impaired amplitude and best in patients with normal amplitude. A similarly graded relationship was not found for categories of speed impairment. The examiner clinical global impression of change mirrored “off” state amplitude but not speed categories. Levodopa, however, normalized speed to a greater extent than amplitude. Our observations suggest that amplitude and speed impairments may be associated with different functional aspects in PD and deserve separate clinical assessment. © 2009 Movement Disorder Society     

Action fluency in Parkinson's disease: a follow-up study.

The impairment in action fluency task present in Parkinson's disease (PD) patients has been previously interpreted as an indicator of conversion from PD to PD with dementia or as a grammatical deficit for verbs and ascribed to a frontostriatal loop pathophysiology. In the present study, 20 patients with PD without dementia were longitudinally tested with overall cognitive decline scales and semantic, letter, and action fluency tasks in a 24-month follow-up study. In comparison with healthy age-matched controls, PD patients showed a stable and consistent impairment on action fluency without any sign of cognitive decline. Our findings suggest that action fluency task may be an early sign of impairment of frontostriatal circuits in PD and it cannot be considered an indicator of conversion from PD to PD with dementia.     

Major depressive disorder in Parkinson's disease: a register-based study

OBJECTIVE: To investigate whether patients with Parkinson's disease (PD) were at an increased risk of developing major depression compared with patients having other medical illnesses with a comparable degree of disability. METHOD: Case register linkage study of Danish Psychiatric Central Register (DPCR)and Danish National Hospital Register (DNHR). Three study cohorts were identified: all patients with PD, osteoarthritis, and diabetes. The rate of discharge diagnosis of depression on re-admission was estimated using competing risks models in survival analyses. The rates for patients with PD were compared with those of patients with osteoarthritis, and diabetes. RESULTS: The study sample identified 211 245 patients in the hospital registers with one of the index diagnoses. An increased incidence of developing depression was found for women and men throughout their lifetime when this incidence was compared with the control groups. CONCLUSION: The findings support the hypothesis that depression in patients with PD is a consequence of brain dysfunction.     

The Sydney multicenter study of Parkinson's disease: The inevitability of dementia at 20 years

After 20 years follow‐up of newly diagnosed patients with Parkinson's disease (PD), 100 of 136 (74%) have died. The mortality rate fell in the first 3 years of treatment, then rose compared to the general population, the standardized mortality ratio from 15 to 20 years reaching 3.1. Drug induced dyskinesia and end of dose failure were experienced by most patients, but the main current problems relate to the non‐levodopa responsive features of the disease. Dementia is present in 83% of 20‐year survivors. Dementia correlates with increasing age and probably reflects an interplay of multiple pathologies. Seventeen people with dementia had postmortems. Eight had diffuse Lewy bodies as the only cause of dementia, while others had mixed neuropathology. Only one person lives independently and 48% are in nursing homes. Excessive daytime sleepiness is noted in 70%, falls have occurred in 87%, freezing in 81%, fractures in 35%, symptomatic postural hypotension in 48%, urinary incontinence in 71%, moderate dysarthria in 81%, choking in 48%, and hallucinations in 74%. The challenge is to understand the cellular mechanisms underlying the diverse features of advanced PD that go far beyond a lack of dopamine. © 2008 Movement Disorder Society