Prevalence, classification, and etiology of pain in Parkinson's disease: association between Parkinson's disease and fibromyalgia or chronic widespread pain

Median nerve ultrasonography in Parkinson's disease: a systematic review and meta-analysis

BACKGROUND

The cross-sectional area (CSA) of the median nerve in Parkinson's disease remains unclear.

OBJECTIVES

This meta-analysis assesses median nerve CSA changes in Parkinson's using ultrasonography.

METHODS

PubMed, Web of Science, Scopus, and EBSCO were selectively searched for literature on Parkinson's disease, Median nerve, and ultrasonography. Following full-text screening, three studies were included in this meta-analysis with 144 Parkinson's disease patients and 127 controls. The primary outcome was the cross-sectional area of the median nerve; other motor parameters were also evaluated.

RESULTS

The cross-sectional area of the median nerve was significantly increased in Parkinson's patients compared to controls (p = 0.007); the standardized mean difference was 0.79 [95% CI (0.21 - 1.37)]. The standardized mean difference of the motor parameters of the median nerve, amplitude, and latency was -0.04 [95% CI (-0.85 to 0.77)] and 0.30 [95% CI (-0.04 to 0.64)], respectively, with statistically insignificant (All p > 0.05).

CONCLUSION

This meta-analysis concluded that the cross-sectional area of the median nerve is increased in Parkinson's disease patients. The increase in the CSA of the median nerve might explain the higher prevalence of carpal tunnel syndrome in Parkinson's disease. Further studies are needed to quantify carpal tunnel syndrome prevalence accurately in Parkinson's.

LIMITATIONS

Heterogeneity exists due to non-standardized CSA calculation methods and varied disease stages. Finger movement during ultrasound may introduce artifacts, compromising CSA measurement accuracy. Establishing a definitive CSA cut-off for carpal tunnel syndrome in Parkinson's requires further investigation.

Pain in monogenic Parkinson's disease: a comprehensive review

Pain, a challenging symptom experienced by individuals diagnosed with Parkinson's disease (PD), still lacks a comprehensive understanding of its underlying pathophysiological mechanisms. A systematic investigation of its prevalence and impact on the quality of life in patients affected by monogenic forms of PD has yet to be undertaken. This comprehensive review aims to provide an overview of the association between pain and monogenic forms of PD, specifically focusing on pathogenic variants in SNCA, PRKN, PINK1, PARK7, LRRK2, GBA1, VPS35, ATP13A2, DNAJC6, FBXO7, and SYNJ1. Sixty-three articles discussing pain associated with monogenic PD were identified and analyzed. The included studies exhibited significant heterogeneity in design, sample size, and pain outcome measures. Nonetheless, the findings of this review suggest that patients with monogenic PD may experience specific types of pain depending on the pathogenic variant present, distinguishing them from non-carriers. For instance, individuals with SNCA pathogenic variants have reported painful dystonia, lower extremity pain, dorsal pain, and upper back pain. However, these observations are primarily based on case reports with unclear prevalence. Painful lower limb dystonia and lower back pain are prominent symptoms in PRKN carriers. A continual correlation has been noted between LRRK2 mutations and the emergence of pain, though the conflicting research outcomes pose challenges in reaching definitive conclusions. Individuals with PINK1 mutation carriers also frequently report experiencing pain. Pain has been frequently reported as an initial symptom and the most troublesome one in GBA1-PD patients compared to those with idiopathic PD. The evidence regarding pain in ATP13A2, PARK7, VPS35, DNAJC6, FBXO7, and SYNJ1pathogenic variants is limited and insufficient. The potential linkage between genetic profiles and pain outcomes holds promising clinical implications, allowing for the potential stratification of patients in clinical trials and the development of personalized treatments for pain in monogenic PD. In conclusion, this review underscores the need for further research to unravel the intricate relationship between pain and monogenic forms of PD. Standardized methodologies, larger sample sizes, and longitudinal studies are essential to elucidate the underlying mechanisms and develop targeted therapeutic interventions for pain management in individuals with monogenic PD.

Antidepressants Effects on Pain in Parkinson Disease: A Systematic Review

OBJECTIVE

Pain in Parkinson disease (PD) is complex as this symptom can be multifactorial in origin because deficits in dopaminergic but also other neurotransmitters are involved. Pain and depression are increasingly recognized to have clinical importance for the quality of life of people living with PD. This systematic review aims to summarize the existing evidence on the potential benefit of using prescribed antidepressants for decreasing or controlling pain associated with PD.

METHODS

PubMed databases were searched for relevant studies using keywords and our exclusion/inclusion criteria and targeting only randomized placebo-controlled trials for antidepressants in PD.

RESULTS

After screening 108 articles, only 3 focused articles were analyzed. Two of the included studies reported were on nortriptyline and paroxetine antidepressants. Unfortunately, included studies did not align in their outcome measures and did not directly compare the drug groups against each other or the placebo. Therefore, the complex nature of the unaligned outcome measures is inadequate for interpreting the efficacy of antidepressants in treating pain symptoms in PD. The third study focused solely on observing the effects of duloxetine but showed no favorable effects of this drug on pain.

CONCLUSIONS

Prospective studies with a direct comparison of antidepressants and placebo should be conducted, focusing on pain-related scales and questions to understand further the role of antidepressants in treating pain in PD.

Fibromyalgia-Like Syndrome Associated with Parkinson's Disease-A Cohort Study

Parkinson’s disease (PD) and fibromyalgia (FM) are two relatively common disorders that are considered distinct diagnoses. The aim of this study was to investigate the epidemiological characteristics of patients with both PD and FM, as well as their comorbidities and medication use. We performed a population-based retrospective cohort study in Israel from 2000 to 2015. We identified patients with PD according to a refined medication tracer algorithm and patients with FM according to their medical records. Using the algorithm, we identified 2606 patients diagnosed with PD, 60 of them (2.3%) were also diagnosed with FM. Most of the patients were females (88.3%) and the mean age of FM diagnosis was 63.95 ± 12.27 years. These patients had a higher prevalence of depression, anxiety, and dementia. Of the patients diagnosed with PD + FM, 46 (76.7%) were diagnosed with FM after the diagnosis of PD. Patients with PD + FM used analgesics of distinct kinds in higher rates, as well as more anti-PD medications. We suggest that patients with PD + FM represent a distinct subgroup with a fibromyalgia-like syndrome associated with Parkinson’s disease (FLISPAD). Their PD is more treatment resistant, and they take more medications, both analgesics and anti-PD.

Negative impact of severity of pain on mood, social life and general activity in Parkinson's disease

OBJECTIVE

Pain is an important non-motor symptom of Parkinson's disease (PD); however, it remains understudied. The purpose of previous studies on the relationship between PD and pain, has been to explore the cause, origin and types of pain. This case control study is designed for clinicians and rehabilitation specialists to effectively identify pain from the patient's point of view. Pain present in PD patients correlates with significant disruption to their daily lives, which was seen by analysing characteristics, frequency, severity and interference of pain.

METHOD

A total of 100 PD patients and 100 control healthy individuals, consisting of 66 males and 34 females were evaluated during routine clinical assessment followed by a neurological exam. The Brief Pain Inventory (BPI) was used to measure chronic pain in terms of pain severity, pain interference and pain frequency between the two groups.

RESULTS

It was determined that PD patients had significantly higher pain severity scores compared to controls (p < 0.05). PD patients with depressive symptoms had significantly higher pain severity and pain interference scores than controls without depressive symptoms. PD patients reported greater scores on Global BPI pain interference and all components of the pain interference subscale.

DISCUSSION

PD and depression seem to be correlated with higher perceived pain, severity and interference. These findings have not been reported by other case control studies, and warrant further causal research into pain, depression and PD.

Comorbid fibromyalgia: A qualitative review of prevalence and importance

Fibromyalgia (FM) may be an unrecognized cause of suffering for persons with an array of medical conditions. This is especially true for illness that is characterized by pain of any nature. Once believed to be a unique diagnosis, FM is recently reported to occur concomitantly with various rheumatic diseases, and importantly adversely impacts global health status. However, there is increasing report of FM associated with other diseases that are not defined by chronic pain. This qualitative review examines the evidence for comorbid FM in illness, and where available the effect of FM on the primary disease. Other than for musculoskeletal disorders, the published literature reporting an association of FM with illness is limited with scanty reports for some neurological, gastrointestinal, mental health and other overlapping pain conditions. Comorbid FM adversely affects both health status and outcome for rheumatic diseases, but with limited study in other diseases. When unrecognized, comorbid FM may be mistaken as poor control of the primary disease, leading to incorrect treatment decisions. FM may be a neglected condition that pervades many conditions and may contribute to the burden of illness. Physicians should be alert to the possibility of comorbid FM, and symptoms of FM should be specifically addressed.

SIGNIFICANCE

Comorbid fibromyalgia (FM) in other medical conditions is largely unrecognized. When reported as accompanying rheumatic diseases, FM adversely affects global health status. With limited reports of comorbid FM with other conditions, neglect to diagnose comorbid FM may misdirect treatments.

Diagnostic confounders of chronic widespread pain: not always fibromyalgia

Although chronic widespread pain is the defining feature of fibromyalgia, a myriad of other conditions may present with similar pain complaint leading to misdiagnosis. Conditions that may mimic fibromyalgia may be categorized as musculoskeletal, neurological, endocrine/metabolic, psychiatric/psychological, and medication related. In this review, we examine these various conditions that should be considered in a differential diagnosis and provide direction that will help the clinician differentiate these conditions from fibromyalgia.

Introduction:

Chronic widespread pain (CWP) is the defining feature of fibromyalgia (FM), a worldwide prevalent condition. Chronic widespread pain is, however, not pathognomonic of FM, and other conditions may present similarly with CWP, requiring consideration of a differential diagnosis.

Objectives:

To conduct a literature search to identify medical conditions that may mimic FM and have highlighted features that may differentiate these various conditions from FM.

Methods:

A comprehensive literature search from 1990 through September 2016 was conducted to identify conditions characterized by CWP.

Results:

Conditions that may mimic FM may be categorized as musculoskeletal, neurological, endocrine/metabolic, psychiatric/psychological, and medication related. Characteristics pertaining to the most commonly identified confounding diagnoses within each category are discussed; clues to enable clinical differentiation from FM are presented; and steps towards a diagnostic algorithm for mimicking conditions are presented.

Conclusion:

Although the most likely reason for a complaint of CWP is FM, this pain complaint can be a harbinger of illness other than FM, prompting consideration of a differential diagnosis. This review should sensitize physicians to a broad spectrum of conditions that can mimic FM.

Evaluation of the safety and immunomodulatory effects of sargramostim in a randomized, double-blind phase 1 clinical Parkinson's disease trial

A potential therapeutic role for immune transformation in Parkinson’s disease evolves from more than a decade of animal investigations demonstrating regulatory T cell (Treg) nigrostriatal neuroprotection. To bridge these results to human disease, we conducted a randomized, placebo-controlled double-blind phase 1 trial with a well-studied immune modulator, sargramostim (granulocyte-macrophage colony-stimulating factor). We enrolled 17 age-matched non-Parkinsonian subjects as non-treated controls and 20 Parkinson’s disease patients. Both Parkinson’s disease patients and controls were monitored for 2 months for baseline profiling. Parkinson’s disease patients were then randomized into two equal groups to self-administer placebo (saline) or sargramostim subcutaneously at 6 μg/kg/day for 56 days. Adverse events for the sargramostim and placebo groups were 100% (10/10) and 80% (8/10), respectively. These included injection site reactions, increased total white cell counts, and upper extremity bone pain. One urticarial and one vasculitis reaction were found to be drug and benzyl alcohol related, respectively. An additional patient with a history of cerebrovascular disease suffered a stroke on study. Unified Parkinson’s disease rating scale, Part III scores in the sargramostim group showed modest improvement after 6 and 8 weeks of treatment when compared with placebo. This paralleled improved magnetoencephalography-recorded cortical motor activities and Treg numbers and function compared with pretreated Parkinson’s disease patients and non-Parkinsonian controls. Peripheral Treg transformation was linked to serum tryptophan metabolites, including L-kynurenine, quinolinic acid, and serotonin. These data offer a potential paradigm shift in modulating immune responses for potential therapeutic gain for Parkinson’s disease. Confirmation of these early study results requires larger numbers of enrolled patients and further clinical investigation.

The immune system modulating drug sargramostim shows promising results in a small clinical trial with Parkinson’s disease (PD) patients. Previous studies have shown that sargramostim increases the number of regulatory T cells, attenuates immune responses, and confers neuroprotection in animal models of neurodegenerative disease. To determine whether these findings translate to humans, Howard E. Gendelman at the University of Nebraska Medical Center, USA, and colleagues examined the effects of sargramostim in 20 patients with PD. Despite the high number of mild to moderate reported adverse events, the drug was generally well tolerated and led to an increase in regulatory T cell number and activity. Moreover, preliminary assessments after 6 and 8 weeks of treatment suggested an overall improvement in the motor skills of patients that received the drug compared with those that received a placebo.

Effect of low-frequency deep brain stimulation on sensory thresholds in Parkinson's disease

OBJECTIVE Chronic pain is a major distressing symptom of Parkinson's disease (PD) that is often undertreated. Subthalamic nucleus (STN) deep brain stimulation (DBS) delivers high-frequency stimulation (HFS) to patients with PD and has been effective in pain relief in a subset of these patients. However, up to 74% of patients develop new pain concerns while receiving STN DBS. Here the authors explore whether altering the frequency of STN DBS changes pain perception as measured through quantitative sensory testing (QST). METHODS Using QST, the authors measured thermal and mechanical detection and pain thresholds in 19 patients undergoing DBS via HFS, low-frequency stimulation (LFS), and off conditions in a randomized order. Testing was performed in the region of the body with the most pain and in the lower back in patients without chronic pain. RESULTS In the patients with chronic pain, LFS significantly reduced heat detection thresholds as compared with thresholds following HFS (p = 0.029) and in the off state (p = 0.010). Moreover, LFS resulted in increased detection thresholds for mechanical pressure (p = 0.020) and vibration (p = 0.040) compared with these thresholds following HFS. Neither LFS nor HFS led to changes in other mechanical thresholds. In patients without chronic pain, LFS significantly increased mechanical pain thresholds in response to the 40-g pinprick compared with thresholds following HFS (p = 0.032). CONCLUSIONS Recent literature has suggested that STN LFS can be useful in treating nonmotor symptoms of PD. Here the authors demonstrated that LFS modulates thermal and mechanical detection to a greater extent than HFS. Low-frequency stimulation is an innovative means of modulating chronic pain in PD patients receiving STN DBS. The authors suggest that STN LFS may be a future option to consider when treating Parkinson's patients in whom pain remains the predominant complaint.

The effects of subthalamic deep brain stimulation on mechanical and thermal thresholds in 6OHDA-lesioned rats

Chronic pain is a major complaint for up to 85% of Parkinson's disease patients; however, it often not identified as a symptom of Parkinson's disease. Adequate treatment of motor symptoms often provides analgesic effects in Parkinson's patients but how this occurs remains unclear. Studies have shown both Parkinson's patients and 6-hydroxydopamine-lesioned rats exhibit decreased sensory thresholds. In humans, some show improvements in these deficits after subthalamic deep brain stimulation, while others report no change. Differing methods of testing and response criteria may explain these varying results. We examined this effect in 6-hydroxydopamine-lesioned rats. Sprague-Dawley rats were unilaterally implanted with subthalamic stimulating electrodes in the lesioned right hemisphere and sensory thresholds were tested using von Frey, tail-flick and hot-plate tests. Tests were done during and off subthalamic stimulation at 50 and 150 Hz to assess its effects on sensory thresholds. The 6-hydroxydopamine-lesioned animals exhibited lower mechanical (left paw, P < 0.01) and thermal thresholds than shams (hot plate, P < 0.05). Both 50 and 150 Hz increased mechanical (left paw; P < 0.01) and thermal thresholds in 6-hydroxydopamine-lesioned rats (hot-plate test: 150 Hz, P < 0.05, 50 Hz, P < 0.01). Interestingly, during von Frey testing, low-frequency stimulation provided a more robust improvement in some 6OHDA lesioned rats, while in others, the magnitude of improvement on high-frequency stimulation was greater. This study shows that subthalamic deep brain stimulation improves mechanical allodynia and thermal hyperalgesia in 6-hydroxydopamine-lesioned animals at both high and low frequencies. Furthermore, we suggest considering using low-frequency stimulation when treating Parkinson's patients where pain remains the predominant complaint.

Is median nerve enlargement at the wrist associated with tremor in Parkinson disease?

OBJECTIVES

Tremor is one of the cardinal features of Parkinson disease (PD) and may cause cumulative trauma-related injury to nerves of the hands. The aim of this study was to assess the electrodiagnostic and sonographic features of patients with PD and to assess the effect of tremor in PD on the median nerve.

METHODS

We studied 31 hands of healthy control participants (n = 16; mean age ± SD, 60.25 ± 14.67 years) and 81 hands of patients with PD (n = 42; 64.95 ± 11.13 years). Motor symptoms were measured by the Unified Parkinson's Disease Rating Scale III. Median nerve conduction studies and sonographic cross-sectional area measurements were performed in all participants.

RESULTS

The median nerve cross-sectional area in patients with PD (10.71 ± 2.79 mm(2)) was significantly larger than that in the control group (7.40 ± 1.05 mm(2); P < .05). However, there was no significant difference in median nerve electrodiagnostic findings between the PD and control groups. The median nerve cross-sectional area was associated with the severity of the tremor but not with the Unified Parkinson's Disease Rating Scale motor score.

CONCLUSIONS

Tremor in PD is associated with median nerve enlargement but not with impairment of median nerve conduction.

Managing palliative care in Parkinson’s disease from diagnosis to end-stage disease: what the clinician should know

SUMMARY Progression of Parkinson’s disease (PD) is followed by aggravation of both motor and non-motor symptoms, which calls for more prominent palliative care towards the end stage of the disease. These palliative services should include multidisciplinary teamwork, in addition to taking into account treatment side effects, dose readjustment, and add-on nonpharmaceutical and pharmaceutical approaches. The treatment protocols in the advanced stage of PD are quite different from the ones in the early stages. The focus is shifted from symptom relief strategies to providing the patient with comfort and support during the palliative stage. In this review, some specific palliative approaches for dealing with motor and non-motor complications of end-stage PD are provided, as well as some general knowledge on palliation.

Stress enhances muscle nociceptor activity in the rat

Chronic widespread pain, such as observed in irritable bowel (IBS) and fibromyalgia (FMS) syndrome, are markedly affected by stress. While such forms of stress-induced hyperalgesia are generally considered manifestations of "central sensitization," recent studies in patients with IBS and FMS suggest an additional, peripheral contribution. To examine the effect of stress on muscle nociceptor function, we evaluated activity in nociceptors innervating the gastrocnemius muscle in an animal model of chronic widespread pain, water avoidance stress, in the rat. This stressor, which produces mechanical hyperalgesia in skeletal muscle produced a significant decrease (∼34%) in mechanical threshold of muscle nociceptors and a marked, ∼two-fold increase in the number of action potentials produced by a prolonged (60 s) fixed intensity suprathreshold 10 g stimulus. Stress also induced an increase in conduction velocity from 1.25 m/s to 2.09 m/s, and increased variability in neuronal activity. Given that these changes, each of at least moderate magnitude, would be expected to enhance nociceptor activity, it is likely that, taken together, they contribute to the enhanced nociception observed in this model of stress-induced chronic widespread pain.