Pain sensitivity and clinical progression in Parkinson's disease

Effectiveness and reliability of hypnosis in stereotaxy: a randomized study

BACKGROUND

Patients suffering from Parkinson's disease (PD) may experience pain during stereotactic frame (SF) fixation in deep brain stimulation (DBS). We assessed the role of hypnosis during the SF fixation in PD patients undergoing awake bilateral subthalamic nucleus (STN) DBS.

METHODS

N = 19 patients were included (N = 13 males, mean age 63 years; N = 10 allocated to the hypnosis and N = 9 allocated to the control groups). Patients were randomly assigned to the interventional (hypnosis and local anesthesia) or non-interventional (local anesthesia only) groups. The primary outcome was the pain perceived (the visual analogue scale (VAS)). Secondary outcomes were stress, anxiety, and depression, as measured by the perceived stress scale (PSS) and hospital anxiety and depression scale (HADS). Procedural distress was measured using the peritraumatic distress inventory (PDI-13).

RESULTS

In the hypnosis group, VASmean was 5.6 ± 2.1, versus 6.4 ± 1.2 in the control group (p = 0.31). Intervention and control groups reported similar VASmax scores (7.6 ± 2.1 versus 8.6 ± 1.6 (p = 0.28), respectively). Both groups had similar HADS scores (6.2 ± 4.3 versus 6.7 ± 1.92, p = 0.72 (HADSa) and 6.7 ± 4.2 versus 7.7 ± 3, p = 0.58 (HADSd)), so were the PSS scores (26.1 ± 6.3 versus 25.1 ± 7, p = 0.75). Evolutions of VASmean (R2 = 0.93, 95% CI [0.2245, 1.825], p = 0.03) and PDI-13 scores (R2 = 0.94, 95% CI [1.006, 6.279], p = 0.02) significantly differ over follow-up with patients in the hypnosis groups showing lower scores.

CONCLUSION

In this unblinded, randomized study, hypnosis does not influence pain, anxiety, and distress during awake SF fixation but modulates pain memory over time and may prevent the integration of awake painful procedures as a bad experience into the autobiographical memory of patients suffering from PD. A randomized controlled study with more data is necessary to confirm our findings.

Deep Brain Stimulation Improves Parkinson's Disease-Associated Pain by Decreasing Spinal Nociception

Dopamine exerts antinociceptive effects on pain in PD at cortical and spinal levels, whereas only cortical effects have been described for DBS, so far. By assessing the nociceptive flexion reflex (NFR) threshold at medication on, and DBS ON and OFF in two patients, we showed that DBS additionally decreases spinal nociception.

Setting the clinical context to non-motor symptoms reflected by Park-pain, Park-sleep, and Park-autonomic subtypes of Parkinson's disease

Non-motor symptoms (NMS) of Parkinson's disease (PD) are well described in both clinical practice and the literature, enabling their management and enhancing our understanding of PD. NMS can dominate the clinical pictures and NMS subtypes have recently been proposed, initially based on clinical observations, and later confirmed in data driven analyses of large datasets and in biomarker-based studies. In this chapter, we provide an update on what is known about three common subtypes of NMS in PD. The pain (Park-pain), sleep dysfunction (Park-sleep), and autonomic dysfunction (Park-autonomic), providing an overview of their individual classification, clinical manifestation, pathophysiology, diagnosis, and potential treatments.

Pain in Parkinson disease: mechanistic substrates, main classification systems, and how to make sense out of them

ABSTRACT

Parkinson disease (PD) affects up to 2% of the general population older than 65 years and is a major cause of functional loss. Chronic pain is a common nonmotor symptom that affects up to 80% of patients with (Pw) PD both in prodromal phases and during the subsequent stages of the disease, negatively affecting patient's quality of life and function. Pain in PwPD is rather heterogeneous and may occur because of different mechanisms. Targeting motor symptoms by dopamine replacement or with neuromodulatory approaches may only partially control PD-related pain. Pain in general has been classified in PwPD according to the motor signs, pain dimensions, or pain subtypes. Recently, a new classification framework focusing on chronic pain was introduced to group different types of PD pains according to mechanistic descriptors: nociceptive, neuropathic, or neither nociceptive nor neuropathic. This is also in line with the International Classification of Disease-11 , which acknowledges the possibility of chronic secondary musculoskeletal or nociceptive pain due to disease of the CNS. In this narrative review and opinion article, a group of basic and clinical scientists revise the mechanism of pain in PD and the challenges faced when classifying it as a stepping stone to discuss an integrative view of the current classification approaches and how clinical practice can be influenced by them. Knowledge gaps to be tackled by coming classification and therapeutic efforts are presented, as well as a potential framework to address them in a patient-oriented manner.

Palliative care in Parkinson disease and related disorders

Although neuropalliative care is a relatively new field, there is increasing evidence for its use among the degenerative parkinsonian syndromes, including idiopathic Parkinson disease, progressive supranuclear palsy, multiple system atrophy, dementia with Lewy bodies, and corticobasal syndrome. This chapter outlines the current state of evidence for palliative care among individuals with the degenerative parkinsonian syndromes with discussion surrounding: (1) disease burden and needs across the conditions; (2) utility, timing, and methods for advance care planning; (3) novel care models for the provision of palliative care; and 4) end-of-life care issues. We also discuss currently unmet needs and unanswered questions in the field, proposing priorities for research and the assessment of implemented care models.

[The new Parkinson's disease pain classification system (PD-PCS)]

BACKGROUND

Chronic pain is a common non-motor symptom in patients with Parkinson's disease (PD).

AIM

To facilitate the diagnosis of pain in PD, we developed a new classification system the Parkinson's disease pain classification system (PD-PCS) and translated the corresponding validated questionnaire into German.

METHODS

A causal relationship of the respective pain syndrome with PD can be determined by four questions before assigning it hierarchically into one of three pain categories (neuropathic, nociceptive and nociplastic).

RESULTS

In the initial validation study 77% of the patients (122/159) had PD-associated pain comprising 87 (55%) with nociceptive, 36 (22%) with nociplastic and 24 (16%) with neuropathic pain. The study revealed a high validity of the questionnaire and a moderate intrarater and interrater reliability. The questionnaire has been adapted into German and employed in 30 patients.

DISCUSSION

The PD-PCS questionnaire is a valid and reliable tool to determine the relationship of a pain syndrome with PD before classifying it according to the underlying category, facilitating further diagnostics and treatment.

Non-pharmacological therapies for pain management in Parkinson's disease: A systematic review

Among the various non-motor symptoms of Parkinson's disease (PD), pain is often cited as the most common and debilitating feature. Currently, the literature contains gaps in knowledge with respect to the various forms of treatment available, particularly non-pharmacological therapies. Thus, the purpose of this systematic review is to provide an examination of the literature on non-pharmacological therapies for pain in PD. We compared the findings of research articles indexed within various literature databases related to non-pharmacological treatments of pain in PD patients. Our review identified five major non-pharmacological methods of pain therapy in PD: acupuncture, hydrotherapy, massage therapy, neuromodulation, and exercise. Treatments such as exercise therapy found a reduction in pain perception due to various factors, including the analgesic effects of neurotransmitter release during exercise and increased activity leading to a decrease in musculoskeletal rigidity and stiffness. By the same token, hydrotherapy has been shown to reduce pain perception within PD patients, with authors often citing a combined treatment of exercise and hydrotherapy as an effective treatment for pain management. Multiple methods of neurostimulation were also observed, including deep brain stimulation and spinal cord stimulation. Deep brain stimulation showed efficacy in alleviating certain pain types (dystonic and central), while not others (musculoskeletal). Hence, patients may consider deep brain stimulation as an additive procedure for their current treatment protocol. On the other hand, spinal cord stimulation showed significant improvement in reducing VAS scores for pain. Finally, although the literature on massage therapy and acupuncture effectiveness on pain management is limited, both have demonstrated a reduction in pain perception, with common reasons such as tactile stimulation and release of anti-nociceptive molecules in the body. Although literature pertaining to non-pharmacological treatments of pain in PD is sparse, there is copious support for these treatments as beneficial to pain management. Further exploration in the form of clinical trials is warranted to assess the efficacy of such therapies.

Diagnosis and Management of Pain in Parkinson's Disease: A New Approach

Pain is a frequent and disabling non-motor feature of Parkinson's disease (PD). The recently proposed PD Pain Classification System (PD-PCS) allows for an association of pain with PD to be determined before being allocated to the main pain mechanism (i.e. nociceptive, neuropathic, and nociplastic). In this article, previous studies on treatments for pain in PD are summarized according to the pain mechanisms. A mechanistic approach to treatment is discussed. We suggest that the first step should be optimizing dopaminergic therapy before other therapy is started. When these treatments remain unsuccessful, further causes of pain must be considered. The role of drugs, invasive treatments, and physiotherapeutic interventions are discussed with a focus on older PD patients and considering polypharmacy, altered pharmacokinetics, and comorbidities.

Pain in Parkinson's disease and the role of the subthalamic nucleus

Pain is a frequent and poorly treated symptom of Parkinson's disease, mainly due to scarce knowledge of its basic mechanisms. In Parkinson's disease, deep brain stimulation of the subthalamic nucleus is a successful treatment of motor symptoms, but also might be effective in treating pain. However, it has been unclear which type of pain may benefit and how neurostimulation of the subthalamic nucleus might interfere with pain processing in Parkinson's disease. We hypothesized that the subthalamic nucleus may be an effective access point for modulation of neural systems subserving pain perception and processing in Parkinson's disease. To explore this, we discuss data from human neurophysiological and psychophysical investigations. We review studies demonstrating the clinical efficacy of deep brain stimulation of the subthalamic nucleus for pain relief in Parkinson's disease. Finally, we present some of the key insights from investigations in animal models, healthy humans and Parkinson's disease patients into the aberrant neurobiology of pain processing and consider their implications for the pain-relieving effects of subthalamic nucleus neuromodulation. The evidence from clinical and experimental studies supports the hypothesis that altered central processing is critical for pain generation in Parkinson's disease and that the subthalamic nucleus is a key structure in pain perception and modulation. Future preclinical and clinical research should consider the subthalamic nucleus as an entry point to modulate different types of pain, not only in Parkinson's disease but also in other neurological conditions associated with abnormal pain processing.

Increased muscle sympathetic nerve activity and impaired baroreflex control in isolated REM-sleep behavior disorder

OBJECTIVE

Changes in baroreflex sensitivity have been reported in patients with idiopathic Parkinson's disease (PD). We sought to investigate the hypothesis that patients with isolated rapid eye movement (REM)-sleep behavior disorder (iRBD), known to be a prodromal stage for PD, will show abnormalities in baroreflex control.

METHODS

Ten iRBD patients were compared to 10 sex- and age-matched healthy controls. Their cardiovascular parameters and muscle sympathetic nerve activity (MSNA) were evaluated at rest and during baroreflex stimulation.

RESULTS

MSNA at rest was higher in iRBD patients (burst frequency [BF]: 44 ± 3 bursts/min; burst incidence [BI]: 60 ± 8 bursts/100 heartbeats) as compared to the controls (BF: 29 ± 3 bursts/min, p < 0.001; BI: 43 ± 9 bursts/100 heartbeats, p < 0.001). During baroreflex stimulation, iRBD patients showed increased absolute values of MSNA (BF: F = 62.728; p < 0.001; BI: F = 16.277; p < 0.001) as compared to the controls. The iRBD patients had decreased diastolic blood pressure at baseline and during lower body negative pressure, but the level of significance was not met.

CONCLUSION

Our study shows increased MSNA and impaired baroreflex control in iRBD patients. We propose that the inhibitory effect of locus coeruleus on baroreflex function might be impaired, leading to the disinhibition of sympathetic outflow.

SIGNIFICANCE

These findings might reflect the destruction of brain areas due to the ascending P-α-synuclein deposits in iRBD patients.

The Parkinson disease pain classification system: results from an international mechanism-based classification approach

ABSTRACT

Pain is a common nonmotor symptom in patients with Parkinson disease (PD) but the correct diagnosis of the respective cause remains difficult because suitable tools are lacking, so far. We developed a framework to differentiate PD- from non-PD-related pain and classify PD-related pain into 3 groups based on validated mechanistic pain descriptors (nociceptive, neuropathic, or nociplastic), which encompass all the previously described PD pain types. Severity of PD-related pain syndromes was scored by ratings of intensity, frequency, and interference with daily living activities. The PD-Pain Classification System (PD-PCS) was compared with classic pain measures (ie, brief pain inventory and McGill pain questionnaire [MPQ], PDQ-8 quality of life score, MDS-UPDRS scores, and nonmotor symptoms). 159 nondemented PD patients (disease duration 10.2 ± 7.6 years) and 37 healthy controls were recruited in 4 centers. PD-related pain was present in 122 patients (77%), with 24 (15%) suffering one or more syndromes at the same time. PD-related nociceptive, neuropathic, or nociplastic pain was diagnosed in 87 (55%), 25 (16%), or 35 (22%), respectively. Pain unrelated to PD was present in 35 (22%) patients. Overall, PD-PCS severity score significantly correlated with pain's Brief Pain Inventory and MPQ ratings, presence of dyskinesia and motor fluctuations, PDQ-8 scores, depression, and anxiety measures. Moderate intrarater and interrater reliability was observed. The PD-PCS is a valid and reliable tool for differentiating PD-related pain from PD-unrelated pain. It detects and scores mechanistic pain subtypes in a pragmatic and treatment-oriented approach, unifying previous classifications of PD-pain.

Towards optimising experimental quantification of persistent pain in Parkinson's disease using psychophysical testing

People with Parkinson's disease (PD) may live for multiple decades after diagnosis. Ensuring that effective healthcare provision is received across the range of symptoms experienced is vital to the individual's wellbeing and quality of life. As well as the hallmark motor symptoms, PD patients may also suffer from non-motor symptoms including persistent pain. This type of pain (lasting more than 3 months) is inconsistently described and poorly understood, resulting in limited treatment options. Evidence-based pain remedies are coming to the fore but therapeutic strategies that offer an improved analgesic profile remain an unmet clinical need. Since the ability to establish a link between the neurodegenerative changes that underlie PD and those that underlie maladaptive pain processing leading to persistent pain could illuminate mechanisms or risk factors of disease initiation, progression and maintenance, we evaluated the latest research literature seeking to identify causal factors underlying persistent pain in PD through experimental quantification. The majority of previous studies aimed to identify neurobiological alterations that could provide a biomarker for pain/pain phenotype, in PD cohorts. However heterogeneity of patient cohorts, result outcomes and methodology between human psychophysics studies overwhelmingly leads to inconclusive and equivocal evidence. Here we discuss refinement of pain-PD paradigms in order that future studies may enhance confidence in the validity of observed effect sizes while also aiding comparability through standardisation. Encouragingly, as the field moves towards cross-study comparison of data in order to more reliably reveal mechanisms underlying dysfunctional pain processing, the potential for better-targeted treatment and management is high.

Chronic pain in Parkinson's disease: Clinical and pathophysiological aspects

Pain is an increasingly recognized non-motor symptom of Parkinson's disease (PD), with significant prevalence and strong impact on quality of life of patients. Moreover, pain can occur with various features in PD and several subtypes may coexist in a same patient, leading to a complex presentation and difficult diagnosis and treatment. In this paper we review the clinical manifestations of painful phenomena in PD, with focus on classifications and algorithms allowing to standardize the diagnosis of pain and PD. We also discuss the pathophysiological mechanisms underlying pain in PD, particularly parkinsonian central pain, in regard to recent clinical, neurophysiological and imaging studies.

Parkinson disease: A systemic review of pain sensitivities and its association with clinical pain and response to dopaminergic stimulation

Patients with Parkinson disease (PD) experience hyperalgesia on evoked pain sensitivity testing, although the relationship of this with persistent pain in PD is less certain. Studies examining this have generated contradictory findings. Further, the role of dopaminergic deficiency as an underlying substrate for hyperalgesia is controversial. We report the results of meta-analyses of the PD pain sensitivity literature in an attempt to answer these questions. We identified 429 records, of which ten articles compared pain sensitivity between PD patients that experienced clinical pain (PDP) to those who did not (PDNP), and twenty studies that examined the effect of dopaminergic medications on pain sensitivity in PD patients. PDP patients experienced a moderate increase in pain sensitivity, had more severe disease, required higher dosages of medication, and were more likely to be female when compared to those PDNP patients. PD patients also had reduced pain sensitivity when tested on dopaminergic medications compared to when they were not on medications. Overall, the results of this systematic review and meta-analysis supports the hypothesis that hyperalgesia contributes to clinical pain in PD, and that the underlying mechanism may be dopaminergically driven.

Clinical pain and functional network topology in Parkinson's disease: a resting-state fMRI study

Pain is an important non-motor symptom in Parkinson's disease (PD), but its underlying pathophysiological mechanisms are still unclear. Research has shown that functional connectivity during the resting-state may be involved in persistent pain in PD. In the present cross-sectional study, 24 PD patients (both during on and off medication phase) and 27 controls participated. We assessed pain with the colored analogue scale and the McGill pain questionnaire. We examined a possible pathophysiological mechanism with resting-state fMRI using functional network topology, i.e., the architecture of functional connections. We took betweenness centrality (BC) to assess hubness, and global efficiency (GE) to assess integration of the network. We aimed to (1) assess the differences between PD patients and controls with respect to pain and resting-state network topology, and (2) investigate how resting-state network topology (BC and GE) is associated with clinical pain in both PD patients and controls. Results show that PD patients experienced more pain than controls. GE of the whole brain was higher in PD patients (on as well as off medication) compared to healthy controls. GE of the specialized pain network was also higher in PD patients compared to controls, but only when patients were on medication. BC of the pain network was lower in PD patients off medication compared to controls. We found a positive association between pain and GE of the pain network in PD patients off medication. For healthy controls, a negative association was found between pain and GE of the pain network, and also between pain and BC of the pain network. Our results suggest that functional network topology differs between PD patients and healthy controls, and that this topology can be used to investigate the underlying neural mechanisms of pain symptoms in PD.

Altered neural responses to heat pain in drug-naive patients with Parkinson disease

Pain is a frequent but still neglected nonmotor symptom of Parkinson disease (PD). However, neural mechanisms underlying pain in PD are poorly understood. Here, we explored whether the high prevalence of pain in PD might be related to dysfunctional descending pain control. Using functional magnetic resonance imaging we explored neural responses during the anticipation and processing of heat pain in 21 PD patients (Hoehn and Yahr I-III) and 23 healthy controls (HC). Parkinson disease patients were naive to dopaminergic medication to avoid confounding drug effects. Fifteen heat pain stimuli were applied to the participants' forearm. Intensity and unpleasantness ratings were provided for each stimulus. Subjective pain perception was comparable for PD patients and HC. Neural processing, however, differed between groups: PD patients showed lower activity in several descending pain modulation regions (dorsal anterior cingulate cortex [dACC], subgenual anterior cingulate cortex, and dorsolateral prefrontal cortex [DLPFC]) and lower functional connectivity between dACC and DLPFC during pain anticipation. Parkinson disease symptom severity was negatively correlated with dACC-DLPFC connectivity indicating impaired functional coupling of pain modulatory regions with disease progression. During pain perception PD patients showed higher midcingulate cortex activity compared with HC, which also scaled with PD severity. Interestingly, dACC-DLPFC connectivity during pain anticipation was negatively associated with midcingulate cortex activity during the receipt of pain in PD patients. This study indicates altered neural processing during the anticipation and receipt of experimental pain in drug-naive PD patients. It provides first evidence for a progressive decline in descending pain modulation in PD, which might be related to the high prevalence of pain in later stages of PD.

Pain sensitivity in Parkinson's disease: Systematic review and meta-analysis

INTRODUCTION

Pain is a common and disabling non-motor symptom of Idiopathic Parkinson's disease (PD) but its underlying pathophysiological mechanisms are not well understood. There is evidence to suggest that altered pain sensitivity may contribute to the experience of pain in PD patients, but clinical studies investigating this have yielded inconsistent results.

OBJECTIVES

To examine whether pain thresholds are altered in PD patients compared to normal healthy controls (HC), via the use of systematic review and meta-analysis.

DATA SOURCES

A systematic search of the MEDLINE and EMBASE library from 1966 to April 2015.

STUDY SELECTION

Studies that compared pain thresholds in PD patients versus HC were included in the systematic review. Additionally, data comparing PD patients off dopaminergic medications (PD_Moff) to HC off medications (HC_Moff) were pooled for meta-analysis by pain modality.

MAIN OUTCOMES

Heat pain threshold, cold pain threshold, electrical pain threshold, nociceptive withdrawal reflex threshold, pressure pain threshold, and pain ratings.

RESULTS

22 studies were reviewed, comprising of 616 PD and 451 HC. In the comparison of PD_Moff versus HC_Moff, a large majority of trials (15/19) found reduced pain thresholds (increased pain sensitivity) in PD patients. Meta-analysis of these trials revealed significantly reduced pain thresholds, of moderate to large effect size, in PD patients across all pain modalities. Results were much more heterogenous when PD patients on medications were compared with HC off medications, with most trials reporting no significant difference in pain thresholds between groups. No significant differences were found in pain thresholds for trials that compared PD patients on medications and HC on medications.

CONCLUSION

PD patients are more sensitive to noxious stimuli compared to HC when tested in the off medication state. This increase in pain sensitivity is observed across all modalities, but is not as apparent when PD patients are administered Levodopa, suggesting that dopamine deficient states may contribute to hyperalgesia. However, it remains to be seen whether or not increased pain sensitivity translates clinically into increased prevalence of pain. Similarly, it is unclear if dopaminergic medications influence pain sensitivity. Performing a meta-analysis on studies comparing pain thresholds in PD patients with and without pain, and on and off dopaminergic medications, may draw more definitive conclusions in this regard.

Understanding and Treating Pain Syndromes in Parkinson's Disease

Pain affects many people with Parkinson's disease (PD) and diminishes their quality of life. Different types of pain have been described, but their related pathophysiological mechanisms remain unclear. The aim of this chapter is to provide movement disorders specialists an update about the pathophysiology of pain and a practical guide for the management of pain syndromes in clinical practice. This chapter reviews current knowledge on the pathophysiological mechanisms of sensory changes and pain in PD, as well as assessment and treatment procedures to manage these symptoms. In summary, changes in peripheral and central pain processing have been demonstrated in PD patients. A decrease in pain threshold and tolerance to several stimuli, a reduced nociceptive withdrawal reflex, a reduced pain threshold, and abnormal pain-induced activation in cortical pain-related areas have been reported. There is no direct association between improvement of motor symptoms and sensory/pain changes, suggesting that motor and nonmotor symptoms do not inevitably share the same mechanisms. Special care in pain assessment in PD is warranted by the specific pathophysiological aspects and the complexity of motor and nonmotor symptoms associated with pain symptoms. Rehabilitation may represent a valid option to manage pain syndromes in PD. However, further research in this field is needed. An integrated approach to pain involving a multidisciplinary team of medical specialists and rehabilitation experts should allow a comprehensive approach to pain in PD.

Pain perception in Parkinson's disease: A systematic review and meta-analysis of experimental studies

While hyperalgesia (increased pain sensitivity) has been suggested to contribute to the increased prevalence of clinical pain in Parkinson's disease (PD), experimental research is equivocal and mechanisms are poorly understood. We conducted a meta-analysis of studies comparing PD patients to healthy controls (HCs) in their response to experimental pain stimuli. Articles were acquired through systematic searches of major databases from inception until 10/2016. Twenty-six studies met inclusion criteria, comprising 1292 participants (PD=739, HCs=553). Random effects meta-analysis of standardized mean differences (SMD) revealed lower pain threshold (indicating hyperalgesia) in PD patients during unmedicated OFF states (SMD=0.51) which was attenuated during dopamine-medicated ON states (SMD=0.23), but unaffected by age, PD duration or PD severity. Analysis of 6 studies employing suprathreshold stimulation paradigms indicated greater pain in PD patients, just failing to reach significance (SMD=0.30, p=0.06). These findings (a) support the existence of hyperalgesia in PD, which could contribute to the onset/intensity of clinical pain, and (b) implicate dopamine deficiency as a potential underlying mechanism, which may present opportunities for the development of novel analgesic strategies.

Distribution and impact on quality of life of the pain modalities assessed by the King's Parkinson's disease pain scale

In Parkinson’s disease, pain is a prevalent and complex symptom of diverse origin. King’s Parkinson’s disease pain scale, assesses different pain syndromes, thus allowing exploration of its differential prevalence and influence on the health-related quality of life of patients. Post hoc study 178 patients and 83 matched controls participating in the King’s Parkinson’s disease pain scale validation study were used. For determining the respective distribution, King’s Parkinson’s disease pain scale items and domains scores = 0 meant absence and ≥1 presence of the symptom. The regular scores were used for the other analyses. Health-related quality of lifewas evaluated with EQ-5D-3L and PDQ-8 questionnaires. Parkinson’s disease patients experienced more pain modalities than controls. In patients, Pain around joints (King’s Parkinson’s disease pain scale item 1) and Pain while turning in bed (item 8) were the most prevalent types of pain, whereas Burning mouth syndrome (item 11) and Pain due to grinding teeth (item 10) showed the lowest frequency. The total number of experienced pain modalities closely correlated with the PDQ-8 index, but not with other variables. For all pain types except Pain around joints (item 1) and pain related to Periodic leg movements/RLS (item 7), patients with pain had significantly worse health-related quality of life. The influence of pain, as a whole, on the health-related quality of life was not remarkable after adjustment by other variables. When the particular types of pain were considered, adjusted by sex, age, and Parkinson’s disease duration, pain determinants were different for EQ-5D-3L and PDQ-8. King’s Parkinson’s disease pain scale allows exploring the distribution of the diverse syndromic pain occurring in Parkinson’s disease and its association with health-related quality of life.

Researchers confirm that the pain experienced by patients with Parkinson disease (PD) is a key determinant of health-related quality of life. Pain is a common non-motor symptom that is often underacknowledged and undertreated. Using data from the recently validated pain scale for PD, Pablo Martinez-Martin (Carlos III Institute of Health in Madrid, Spain) and colleagues explored the impact of specific pain modalities on patients’ quality of life. They found that patients with PD reported experiencing twice as many types of pain than controls, with pain around the joints and pain while moving in bed being the most prevalent. Furthermore, there was a close correlation between the number of experienced pain modalities and quality of life as evaluated with the PD questionnaire PDQ-8. Understanding the different types of pain in PD will aid the provision of effective pain relief and greatly improve patients’wellbeing.

Is increased spinal nociception another hallmark for Parkinson's disease?

Augmented spinal nociception during the "off" phase has been observed early in Parkinson's disease further increasing with disease duration. To find out whether increased spinal nociception represents a premotor feature, experimental pain sensitivity was assessed in idiopathic REM-sleep behavior disorder (IRBD) patients with or without signs of a neurodegenerative disorder compared to early Parkinson's disease (ePD) patients and healthy controls (HC). Spinal nociception as measured by the nociceptive flexion reflex (NFR) and experimental pain sensitivity as measured by heat and electrical pain thresholds were determined in 14 IRBD, 15 ePD patients in the medication-defined "off" state and 27 HC in an explorative cohort study. No significant differences between IRBD and HC were found with regard to spinal nociception (NFR) and experimental pain sensitivity. However, IRBD patient with anosmia and/or abnormal DaTSCAN tended to increased experimental pain sensitivity. In contrast, early PD patients exhibited increased NFR responses compared to HC, and a tendency for increased spinal nociception compared to IRBD patients. Increased spinal nociception may represent an early but not a premotor, non-motor feature of PD. Whether increased pain sensitivity already presents a premotor feature should be assessed in further studies.

Restoring Spinal Noradrenergic Inhibitory Tone Attenuates Pain Hypersensitivity in a Rat Model of Parkinson's Disease

In the present study, we investigated whether restoring descending noradrenergic inhibitory tone can attenuate pain in a PD rat model, which was established by stereotaxic infusion of 6-hydroxydopamine (6-OHDA) into the bilateral striatum (CPu). PD rats developed thermal and mechanical hypersensitivity at the 4th week after surgery. HPLC analysis showed that NE content, but not dopamine or 5-HT, significantly decreased in lumbar spinal cord in PD rats. Additional noradrenergic depletion by injection of N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) aggravated pain hypersensitivity in PD rats. At the 5th week after injection of 6-OHDA, systemic treatment with pharmacological norepinephrine (NE) precursor droxidopa (L-DOPS) or α2 adrenoceptor agonist clonidine significantly attenuated thermal and mechanical pain hypersensitivity in PD rats. Furthermore, application of norepinephrine (NE) and 5-hydroxytryptamine (5-HT) reuptake inhibitors duloxetine, but not 5-HT selective reuptake inhibitors sertraline, significantly inhibited thermal and mechanical pain hypersensitivity in PD rats. Systemic administration of Madopar (L-DOPA) or the D2/D3 agonist pramipexole slightly inhibited the thermal, but not mechanical, hypersensitivity in PD rats. Thus, our study revealed that impairment of descending noradrenergic system may play a key role in PD-associated pain and restoring spinal noradrenergic inhibitory tone may serve as a novel strategy to manage PD-associated pain.

Pain in Parkinson's Disease: Current Concepts and a New Diagnostic Algorithm

Background

Pain is a significant burden for patients with Parkinson's disease (PD) with a high impact on quality of life. The present article aims at summarizing epidemiological, pathophysiological, clinical, and neurophysiological data regarding pain in PD.

Methods

In this domain, a procedure of systematic assessment is still lacking for the syndromic diagnosis and should take into account pain characteristics, effects of dopaminergic treatment, motor fluctuations, and non-PD-associated pain.

Findings

We propose an original questionnaire addressing an algorithm suitable for daily clinical practice. The questionnaire is based on a three-step approach addressing first the relationship between pain and PD (including temporal relationship with the course of the disease, association with motor fluctuations, and impact of antiparkinsonian treatment), before classifying pain into one of three main syndromes (i.e., musculoskeletal pain, psychomotor restlessness pain, and neuropathic pain).

Conclusions

The proposed questionnaire allows the characteristics of each pain type to be determined according to its relationship with the disease and its treatment. The validation of the clinical use of this questionnaire will be the goal of a forthcoming work.

The development of delusion revisited: a transdiagnostic framework

This study proposes a transdiagnostic framework for delusion development, analysing psychiatric (schizophrenia, bipolar disorder, major depressive disorder) and neurological disorders (stroke, and neurodegenerative diseases) in which delusions are predominant. Our aim is to identify a transdiagnostic core of neural and cognitive alterations associated with delusions across distinct clinical disorders. Reviewed empirical evidence suggests delusions are associated: on the neural level with changes in the ventromedial prefrontal cortex (vmPFC) networks, and on the neuropsychological level with dysfunction in the processes (generation of affective value, the construction of internal models of the world, and the reflection about Self and/or Other's mental states) that these network mediate. The concurrent aberration of all these processes could be critical for the clinical transition to a psychotic delusional state. In particular, delusions could become clinically manifest when (1) stimuli are attributed an aberrant affective salience, that (2) is explained by the patient within distorted explanatory internal models that (3) are poorly inhibited by cognitive control systems. This framework extends the two-factor account of delusion model and suggests that common neural mechanisms for the delusions in psychiatric and in neurological disorders.

Prevalence of headache in patients with Parkinson's disease and its association with the side of motor symptom onset

We compared the lifetime prevalence and the prevalence of headache during the previous year in patients with Parkinson's disease (PD) and control subjects. We also investigated the association between the side of PD symptom onset and the side of the headache. We interviewed 98 consecutive patients with an established diagnosis of PD between December 2010 and January 2012. The control group consisted of the 98 oldest sex-matched individuals from the nationwide Brazilian headache database. PD patients showed a significantly lower prevalence (40.8%) of headache in the previous year than controls (69.4%) (adjusted OR 0.5, CI 95% 0.2-0.9, p = 0.03). PD patients also showed a lower prevalence of headache throughout life (74.5%) than controls (93.9%) (adjusted OR 0.2, CI 95% 0.1-0.6, p = 0.01). Considering only patients who presented headache during the previous year, PD patients showed a higher association with occurrence of migraine than tension-type headache compared with controls (adjusted OR 3.3, CI 95% 1.2-8.9, p = 0.02). The headache side was ipsilateral to the side of PD onset in 21 patients (84%), with a concordance of 85.7% on the left side and 81.8% on the right side (p < 0.01). The prevalence of primary headache was significantly lower in patients with PD than controls. The predominant side of headache was ipsilateral to the side of initial motor signs of PD.

Pain perception in patients with Parkinson's disease

Abnormalities in pain perception are a part of the clinical picture in Parkinson's disease (PD) and belong to the category of non-motor symptoms. Two groups of patients were included in this study: (i) an experimental group of 36 patients with PD who were eligible for subthalamic deep brain stimulation (the experimental group [EG]) and (ii) a control group (CG) of 34 patients with a space-occupying lesion who were admitted for a framed stereotactic biopsy. Stereotactic frame fixation was used in both groups as a nociceptive stimulus. All participants were assessed for pain perception with two kinds of visual analogue scales (VAS) (a non-color VAS [ncVAS] and a color VAS [cVAS]) immediately after the stimulus (EG - ncVAS 1 and cVAS 1; CG - ncVAS 3 and cVAS 3) and 24 hours later (EG - ncVAS 2 and cVAS 2; CG - ncVAS 4 and cVAS 4). The means for the two pain scores assessed directly after frame fixation were 3.59 (ncVAS 1) and 3.06 (cVAS 1) for patients in the EG, while the mean ncVAS was 3, and the mean cVAS 3 was 6.1 for those in the CG. The pain intensity was significantly lower for patients with PD (EG) compared to those in the CG for both ncVAS and cVAS (p<0.05 for each measure). The mean pain scores for ncVAS and cVAS measured 24 hours after the procedure were 3.18 and 2.79 for patients with PD (EG) and 6.10 and 5.77 for those in the CG, respectively. Pain intensity measured 24 hours after the procedure was significantly lower in those with PD (EG) compared to the CG. This study has demonstrated that pain perception in patients with PD is significantly lower than pain perception in non-parkinsonian patients.

Spinal cord lesions in sporadic Parkinson's disease

In this autopsy-based study, α-synuclein immunohistochemistry and lipofuscin pigment-Nissl architectonics in serial sections of 100 μm thickness were used to investigate the spinal cords and brains of 46 individuals: 28 patients with clinically and neuropathologically confirmed Parkinson's disease, 6 cases with incidental Lewy body disease, and 12 age-matched controls. α-Synuclein inclusions (particulate aggregations, Lewy neurites/bodies) in the spinal cord were present between neuropathological stages 2-6 in all cases whose brains were staged for Parkinson's disease-related synucleinopathy. The only individuals who did not have Lewy pathology in the spinal cord were a single stage 1 case (incidental Lewy body disease) and all controls. Because the Parkinson's disease-related lesions were observable in the spinal cord only after Lewy pathology was seen in the brain, it could be concluded that, within the central nervous system, sporadic Parkinson's disease does not begin in the spinal cord. In addition: (1) α-Synuclein-immunoreactive axons clearly predominated over Lewy bodies throughout the spinal cord and were visible in medial and anterior portions of the anterolateral funiculus. Their terminal axons formed dense α-synuclein-immunoreactive networks in the gray matter and were most conspicuous in the lateral portions of layers 1, 7, and in the cellular islands of layer 9. (2) Notably, this axonopathy increased remarkably in density from cervicothoracic segments to lumbosacral segments of the cord. (3) Topographically, it is likely that the spinal cord α-synuclein immunoreactive axonal networks represent descending projections from the supraspinal level setting nuclei (locus coeruleus, lower raphe nuclei, magnocellular portions of the reticular formation). (4) Following the appearance of the spinal cord axonal networks, select types of projection neurons in the spinal cord gray matter displayed α-synuclein-immunoreactive inclusions: chiefly, nociceptive neurons of the dorsal horn in layer 1, sympathetic and parasympathetic preganglionic neurons in layer 7, the cellular pools of α-motoneurons in layer 9, and the smaller motoneurons in Onuf's nucleus in layer 9 (ventral horn). The spinal cord lesions may contribute to clinical symptoms (e.g., pain, constipation, poor balance, lower urinary tract complaints, and sexual dysfunction) that occur during the premotor and motor phases of sporadic Parkinson's disease.

Subthalamic deep brain stimulation modulates small fiber-dependent sensory thresholds in Parkinson's disease

The effects of deep brain stimulation of the subthalamic nucleus on nonmotor symptoms of Parkinson's disease (PD) rarely have been investigated. Among these, sensory disturbances, including chronic pain (CP), are frequent in these patients. The aim of this study was to evaluate the changes induced by deep brain stimulation in the perception of sensory stimuli, either noxious or innocuous, mediated by small or large nerve fibers. Sensory detection and pain thresholds were assessed in 25 PD patients all in the off-medication condition with the stimulator turned on or off (on- and off-stimulation conditions, respectively). The relationship between the changes induced by surgery on quantitative sensory testing, spontaneous CP, and motor abilities were studied. Quantitative sensory test results obtained in PD patients were compared with those of age-matched healthy subjects. Chronic pain was present in 72% of patients before vs 36% after surgery (P=.019). Compared with healthy subjects, PD patients had an increased sensitivity to innocuous thermal stimuli and mechanical pain, but a reduced sensitivity to innocuous mechanical stimuli. In addition, they had an increased pain rating when painful thermal stimuli were applied, particularly in the off-stimulation condition. In the on-stimulation condition, there was an increased sensitivity to innocuous thermal stimuli but a reduced sensitivity to mechanical or thermal pain. Pain provoked by thermal stimuli was reduced when the stimulator was turned on. Motor improvement positively correlated with changes in warm detection and heat pain thresholds. Subthalamic nucleus deep brain stimulation contributes to relieve pain associated with PD and specifically modulates small fiber-mediated sensations.