Chronic pain and pain processing in Parkinson’s disease

Pain is experienced by the vast majority of patients living with Parkinson’s disease. It is most often of nociceptive origin, but may also be ascribed to neuropathic (radicular or central) or miscellaneous sources. The recently validated King’s Parkinson’s Disease Pain Scale is based on 7 domains including musculoskeletal pain, chronic body pain (central or visceral), fluctuation-related pain, nocturnal pain, oro-facial pain, pain with discolouration/oedema/swelling, and radicular pain. The basal ganglia integrate incoming nociceptive information and contribute to coordinated motor responses in pain avoidance and nocifensive behaviors. In Parkinson’s disease, nigral and extra-nigral pathology, involving cortical areas, brainstem nuclei, and spinal cord, may contribute to abnormal central nociceptive processing in patients experiencing pain or not. The dopamine deficit lowers multimodal pain thresholds that are amenable to correction following levodopa dosing. Functional brain imaging with positron emission tomography following administration of H215O revealed abnormalities in the sensory discriminative processing of pain (insula/SII), as well as in the affective motivational processing of pain (anterior cingulate cortex, prefrontal cortex). Pain management is dependent on efforts invested in diagnostic accuracy to distinguish nociceptive from neuropathic pain. Treatment requires an integrated approach including strategies to lessen levodopa-related response fluctuations, in addition to other pharmacological and non-pharmacological options such as deep brain stimulation and rehabilitation

Emerging analgesic drugs for Parkinson's disease

Introduction: Pain affects between 40 and 85% of Parkinson's disease (PD) patients. It is a frequently disabling and overlooked feature, which can significantly reduce health-related quality of life. Unfortunately, there are no universally recommended treatments for this condition. Areas covered: Evidence about the efficacy and safety of available analgesic treatments is summarized in this review. Potential targets for upcoming therapies are then discussed in light of what is currently known about the physiopathology of pain in PD. Protocols for efficacy and safety assessment of novel analgesic therapies are discussed. Finally, critical aspects of study protocol design such as patient selection or outcomes to be evaluated are discussed. Expert opinion: Preliminary results indicate that duloxetine, cranial electrotherapy stimulation, rotigotine, subthalamic or pallidum nuclei stimulation or lesion or levodopa could be effective for treating pain in PD. Similarly, some case reports indicate that repetitive transcranial magnetic stimulation (rTMS) or apomorphine could be effective for relieving painful off-period dystonia. Clinical trials with rTMS or oxycodone/naloxone prolonged-release tablets for neuropathic pain or botulinum toxin for off-period dystonia are underway. Success of clinical trials about analgesic strategies in PD will depend on the selection of the right PD population to be treated, according to the type of pain, and the proper selection of study outcomes and follow-up of international recommendations.Fil: Perez Lloret, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Centre National de la Recherche Scientifique; Francia. Université Toulouse III Paul Sabatier; Francia. Fundación para la Lucha Contra las Enfermedades Neurológicas de la Infancia. Instituto de Investigaciones Neurológicas "Raúl Carrea"; ArgentinaFil: Rey, María Verónica. Centre National de la Recherche Scientifique; Francia. Université Toulouse III Paul Sabatier; Francia. Fundación para la Lucha Contra las Enfermedades Neurológicas de la Infancia. Instituto de Investigaciones Neurológicas "Raúl Carrea"; ArgentinaFil: Dellapina, Estelle. Université Toulouse III Paul Sabatier; FranciaFil: Pellaprat, Jean. Université Toulouse III Paul Sabatier; FranciaFil: Brefel Courbon, Christine. Centre National de la Recherche Scientifique; Francia. Université Toulouse III Paul Sabatier; FranciaFil: Rascol, Olivier. Centre National de la Recherche Scientifique; Francia. Université Toulouse III Paul Sabatier; Franci

Prevalence and pharmacological factors associated with impulse-control disorder symptoms in patients with parkinson disease

BACKGROUND: Impulse-control disorders (ICDs) occur in patients with Parkinson disease (PD), especially in younger patients on dopamine therapies. OBJECTIVE: To assess the prevalence of ICD symptoms and its pharmacological correlations in a sample of French patients with PD and without PD (poststroke). METHODS: Outpatients with PD and without PD (poststroke) were screened for compulsive behaviors related to hypersexuality, compulsive shopping, pathological gambling, or compulsive eating by means of the Questionnaire for Impulse-Control Disorders-short version. Full medical history and Unified Parkinson's Disease Rating Scale scores were also recorded. Dose of dopamine agonists were converted to defined daily doses (DDDs), according to the World Health Organization Anatomical Therapeutic Chemical classification system classification system. RESULTS: Two hundred three patients with PD and 52 patients without PD were recruited (mean ± SD age, 67 ± 1 vs 69 ± 2, P= 0.4; males: 62% vs 55% P= 0.2). Symptoms of ICDs were reported by 0% of poststroke patients and 25% of the patients with PD (P < 0.001). Hypersexuality was reported by 10% of the patients with PD, compulsive shopping by 6%, pathological gambling by 3%, and compulsive eating by 14%. A logistic regression analysis found that age younger than 68 years (odds ratio [OR], 3.3; 95% confidence interval, 1.6-6.6) and exposure to dopamine agonists (OR, 20.3; 95% confidence interval, 2.7-65.0) or monoaminooxidase-B inhibitor (OR, 3.7; 95% confidence interval, 1.1-12.6) were significant factors associated with increased ICD frequency. Patients with ICD symptoms were exposed to higher dopamine doses than those without them (1.6 ± 0.1 vs 1.0 ± 0.1 daily-defined doses; P < 0.001). A dose-response pharmacodynamic model disclosed a significant nonlinear dose-response relationship between dopamine agonists and frequency of ICD symptoms (P < 0.01). CONCLUSIONS: Impulse-control disorder symptoms were more frequent in the patients with PD than in the poststroke patients with PD. Impulse-control disorder symptoms were related to younger age and exposure to monoaminooxidase-B inhibitors, and showed a nonlinear dose-response relationship with dopamine agonists.Fil: Perez Lloret, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Inserm; FranciaFil: Rey, María Verónica. Inserm; FranciaFil: Fabre, Nelly. No especifíca;Fil: Ory, Fabienne. No especifíca;Fil: Spampinato, Umberto. No especifíca;Fil: Brefel Courbon, Christine. No especifíca;Fil: Montastruc, Jean Louis. No especifíca;Fil: Rascol, Olivier. Inserm; Franci

Broad white matter impairment in multiple system atrophy.

Multiple system atrophy (MSA) is a rare neurodegenerative disorder characterized by the widespread aberrant accumulation of α-synuclein (α-syn). MSA differs from other synucleinopathies such as Parkinson's disease (PD) in that α-syn accumulates primarily in oligodendrocytes, the only source of white matter myelination in the brain. Previous MSA imaging studies have uncovered focal differences in white matter. Here, we sought to build on this work by taking a global perspective on whole brain white matter. In order to do this, in vivo structural imaging and diffusion magnetic resonance imaging were acquired on 26 MSA patients, 26 healthy controls, and 23 PD patients. A refined whole brain approach encompassing the major fiber tracts and the superficial white matter located at the boundary of the cortical mantle was applied. The primary observation was that MSA but not PD patients had whole brain deep and superficial white matter diffusivity abnormalities (p < .001). In addition, in MSA patients, these abnormalities were associated with motor (Unified MSA Rating Scale, Part II) and cognitive functions (Mini-Mental State Examination). The pervasive whole brain abnormalities we observe suggest that there is widespread white matter damage in MSA patients which mirrors the widespread aggregation of α-syn in oligodendrocytes. Importantly, whole brain white matter abnormalities were associated with clinical symptoms, suggesting that white matter impairment may be more central to MSA than previously thought

Leucine-Rich Glioma-Inactivated 1 Encephalitis: Broadening the Sphere

Background: Leucine-rich glioma-inactivated 1 (LGI1) encephalitis is a rare entity. Its typical features are seizures, faciobrachial dystonic seizures (FBDS), cognitive impairment, and personality changes. Case report: We report the case of a 66-year-old man with an unusual presentation, consisting of two types of FBDS, one starting in the foot and the other consisting of asynchronous myoclonic and dystonic jerks of the face triggered by noise and chin stimulation. The patient displayed no personality changes or cognitive impairment. Discussion: LGI1 encephalitis is a heterogeneous disease. Many different forms of FBDS may be observed, and these seizures can be the only symptom. This type of encephalitis should be suspected in presenting very frequent episodic events with dystonic features, regardless of the part of the body affected

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

Recovery of cortical effective connectivity and recovery of consciousness in vegetative patients

Patients surviving severe brain injury may regain consciousness without recovering their ability to understand, move and communicate. Recently, electrophysiological and neuroimaging approaches, employing simple sensory stimulations or verbal commands, have proven useful in detecting higher order processing and, in some cases, in establishing some degree of communication in brain-injured subjects with severe impairment of motor function. To complement these approaches, it would be useful to develop methods to detect recovery of consciousness in ways that do not depend on the integrity of sensory pathways or on the subject's ability to comprehend or carry out instructions. As suggested by theoretical and experimental work, a key requirement for consciousness is that multiple, specialized cortical areas can engage in rapid causal interactions (effective connectivity). Here, we employ transcranial magnetic stimulation together with high-density electroencephalography to evaluate effective connectivity at the bedside of severely brain injured, non-communicating subjects. In patients in a vegetative state, who were open-eyed, behaviourally awake but unresponsive, transcranial magnetic stimulation triggered a simple, local response indicating a breakdown of effective connectivity, similar to the one previously observed in unconscious sleeping or anaesthetized subjects. In contrast, in minimally conscious patients, who showed fluctuating signs of non-reflexive behaviour, transcranial magnetic stimulation invariably triggered complex activations that sequentially involved distant cortical areas ipsi- and contralateral to the site of stimulation, similar to activations we recorded in locked-in, conscious patients. Longitudinal measurements performed in patients who gradually recovered consciousness revealed that this clear-cut change in effective connectivity could occur at an early stage, before reliable communication was established with the subject and before the spontaneous electroencephalogram showed significant modifications. Measurements of effective connectivity by means of transcranial magnetic stimulation combined with electroencephalography can be performed at the bedside while by-passing subcortical afferent and efferent pathways, and without requiring active participation of subjects or language comprehension; hence, they offer an effective way to detect and track recovery of consciousness in brain-injured patients who are unable to exchange information with the external environment

Revealing a novel nociceptive network that links the subthalamic nucleus to pain processing

Pain is a prevalent symptom of Parkinson's disease, and is effectively treated by deep brain stimulation of the subthalamic nucleus (STN). However, the link between pain and the STN remains unclear. In the present work, we report that STN neurons exhibit complex tonic and phasic responses to noxious stimuli using in vivo electrophysiology in rats. We also show that nociception is altered following lesions of the STN, and characterize the role of the superior colliculus and the parabrachial nucleus in the transmission of nociceptive information to the STN, physiologically from both structures and anatomically in the case of the parabrachial nucleus. We show that STN nociceptive responses are abnormal in a rat model of PD, suggesting their dependence on the integrity of the nigrostriatal dopaminergic system. The STN-linked nociceptive network we reveal is likely to be of considerable clinical importance in neurological diseases involving a dysfunction of the basal ganglia