The impact of Alzheimer's disease on the functional connectivity between brain regions underlying pain perception

Perspectives on pain in Down syndrome

Down syndrome (DS) or trisomy 21 is a genetic condition often accompanied by chronic pain caused by congenital abnormalities and/or conditions, such as osteoarthritis, recurrent infections, and leukemia. Although DS patients are more susceptible to chronic pain as compared to the general population, the pain experience in these individuals may vary, attributed to the heterogenous structural and functional differences in the central nervous system, which might result in abnormal pain sensory information transduction, transmission, modulation, and perception. We tried to elaborate on some key questions and possible explanations in this review. Further clarification of the mechanisms underlying such abnormal conditions induced by the structural and functional differences is needed to help pain management in DS patients.

Korsakoff syndrome and altered pain perception: a search of underlying neural mechanisms

OBJECTIVES

Patients with Korsakoff syndrome (KS) may have a diminished pain perception. Information on KS and pain is scarce and limited to case descriptions. The present study is the first to investigate the underlying neural mechanisms of altered pain perception in patients with KS more systematically.

METHODS

We conducted a literature search on neural correlates of pain perception in other neurocognitive disorders in which extensive research was done.

RESULTS

The brain areas that are affected in KS showed considerable overlap with the neural correlates of pain perception in other neurocognitive disorders. We discussed which different aspects of disturbed pain perception could play a role within KS, based on distinct neural damage and brain areas involved in pain perception.

CONCLUSIONS

Combining current knowledge, we hypothesize that diminished pain perception in KS may be related to lesioned neural connections between cerebral cortical networks and relays of mainly the thalamus, the periaqueductal gray, and possibly lower brain stem regions projecting to the cerebellum. Based on these neural correlates of altered pain perception, we assume that increased pain thresholds, inhibition of pain signals, and disturbed input to cerebral and cerebellar cortical areas involved in pain processing, all are candidate mechanisms in cases of diminished pain perception in KS. We recommend that clinicians need to be alert for somatic morbidity in patients with KS. Due to altered neural processing of nociceptive input the clinical symptoms of somatic morbidity may present differently (i.e. limited pain responses) and therefore are at risk of being missed.

Increased pain unpleasantness and pain-related fMRI activation in the periaqueductal gray in Alzheimer's disease

Background

Pain continues to be underrecognized and undertreated in people with Alzheimer's disease (AD). The periaqueductal gray (PAG) is essential to pain processing and modulation yet is damaged by AD. While evidence exists of altered neural processing of pain in AD, there has not been a focused investigation of the PAG during pain in people with AD.

Purpose

To investigate the role of the PAG in sensory and affective pain processing for people living with AD.

Methods

Participants from a larger study completed pain psychophysics assessments and then a perceptually-matched heat pain task (warmth, mild, and moderate pain) during a functional MRI scan. In this cross-sectional study, we examined blood oxygenation level-dependent (BOLD) responses in the PAG and other pain-related regions in participants with AD (n = 18) and cognitively intact older adults (age- and sex-matched, n = 18). Associations of BOLD percent signal change and psychophysics were also examined.

Results

There were significant main effects of AD status on the temperature needed to reach each perception of warmth or pain, where people with AD reached higher temperatures. Furthermore, participants with AD rated mild and moderate pain as more unpleasant than controls. PAG BOLD activation was greater in AD relative to controls during warmth and mild pain percepts. No significant differences were found for moderate pain or in other regions of interest. Greater PAG activation during mild pain was associated with higher affective/unpleasantness ratings of mild pain in participants with AD but not in controls.

Conclusion

Results suggest a role for the PAG in altered pain responses in people with AD. The PAG is the primary source of endogenous opioid pain inhibition in the neuroaxis, thus, altered PAG function in AD suggests possible changes in descending pain inhibitory circuits. People with AD may have a greater risk of suffering from pain compared to cognitively intact older adults.

Faces of Pain in Dementia: Learnings From a Real-World Study Using a Technology-Enabled Pain Assessment Tool

Pain is common in people living with dementia (PLWD), including those with limited verbal skills. Facial expressions are key behavioral indicators of the pain experience in this group. However, there is a lack of real-world studies to report the prevalence and associations of pain-relevant facial micro-expressions in PLWD. In this observational retrospective study, pain-related facial features were studied in a sample of 3,144 PLWD [mean age 83.3 years (SD = 9.0); 59.0% female] using the Face domain of PainChek®, a point-of-care medical device application. Pain assessments were completed by 389 users from two national dementia-specific care programs and 34 Australian aged care homes. Our analysis focused on the frequency, distribution, and associations of facial action units [AU(s)] with respect to various pain intensity groups. A total of 22,194 pain assessments were completed. Of the AUs present, AU7 (eyelid tightening) was the most frequent facial expression (48.6%) detected, followed by AU43 (closing eyes; 42.9%) and AU6 (cheek raising; 42.1%) during severe pain. AU20 (horizontal mouth stretch) was the most predictive facial action of higher pain scores. Eye-related AUs (AU6, AU7, AU43) and brow-related AUs (AU4) were more common than mouth-related AUs (e.g., AU20, AU25) during higher pain intensities. No significant effect was found for age or gender. These findings offer further understanding of facial expressions during clinical pain in PLWD and confirm the usefulness of artificial intelligence (AI)-enabled real-time analysis of the face as part of the assessment of pain in aged care clinical practice.

A Cross-Sectional Study of Pain Sensitivity and Unpleasantness in People with Vascular Dementia

OBJECTIVE

Advanced age holds higher risk of both pain and dementia, with many studies finding dementia often heightens sensitivity to pain. VaD is the second most common type of dementia. Only a few observational or retrospective studies have examined pain responsiveness in VaD, suggesting it may increase pain unpleasantness (i.e., pain affect). This study compared thermal pain psychophysics between a cohort of vascular dementia (VaD) patients and healthy control (HC) subjects.

DESIGN

Single center, cross-sectional, between-subjects design.

SUBJECTS

Verbally communicative, probable VaD patients (N = 23) and age- and sex-matched HC (N = 23).

METHODS

A thermal psychophysics protocol assessed "mild pain" and "moderate pain" thresholds (oC temperature) and associated unpleasantness ratings (0-20 scale) in both VaD and HC groups. Psychophysics were compared between groups by way of a mixed-effects analysis, controlling for depressive symptoms.

RESULTS

There were no significant differences between groups for pain thresholds (main effect p = 0.086, Cohen's d: mild = 0.55, moderate = 0.27). However, unpleasantness ratings were higher in the VaD group compared to HC (main effect p = 0.003; mild pain p = 0.022, Cohen's d = 0.79; moderate pain p = 0.057, Cohen's d = 0.6).

CONCLUSIONS

These results are consistent with prior observational findings suggesting VaD may make patients more susceptible to pain, particularly its affective component.

Patterns of cognitive decline and somatosensory processing in a mouse model of amyloid accumulation

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Despite copious amyloid plaques, 5XFAD mice show modest signs of cognitive decline.

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At ages 2 to 13 months old 5XFAD mice show no signs of sensory or pain dysfunctions.

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5XFAD mice may not be a valid model for pain abnormalities in the context of AD.

Pain and cognitive decline increase with age. In particular, there is a troubling relationship between dementia and pain, with some studies showing higher prevalence and inadequate treatment of pain in this population. Alzheimer’s disease (AD) is one of the most common causes of dementia in older adults. Amyloid plaques are a hallmark of AD. The downstream processes these plaques promote are believed to affect neuronal and glial health and activity. There is a need to better understand how the neuropathological changes of AD shape neural activity and pain sensitivity. Here, we use the 5XFAD mouse model, in which dense amyloid accumulations occur at early ages, and in which previous studies reported signs of cognitive decline. We hypothesized that 5XFAD mice develop sensory and pain processing dysfunctions. Although amyloid burden was high throughout the brain, including in regions involved with sensory processing, we identified no functionally significant differences in reflexive or spontaneous signs of pain. Furthermore, expected signs of cognitive decline were modest; a finding consistent with variable results in the literature. These data suggest that models recapitulating other pathological features of Alzheimer’s disease might be better suited to studying differences in pain perception in this disease.

Spinal beta-amyloid1-42 acts as an endogenous analgesic peptide in CCI-induced neuropathic pain

BACKGROUND

The mechanism for reduced pain sensitivity associated with Alzheimer's disease (AD) has not been illustrated. We hypothesize that amyloid beta 1-42 (Aβ1-42) in the spinal cord acts as an endogenous analgesic peptide to suppress pain induced by nerve injury.

METHODS

We used chronic constriction injury of the sciatic nerve (CCI) to produce neuropathic pain in Sprague-Dawley rats. Enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry were used to determine the level of Aβ1-42, the expression of Wnt3a/5b and glial activation in the spinal cord. Western blotting was used to determine the expression of interleukins, the phosphorylation of NR2B and ERK1/2, and the nuclear accumulation of transcriptional factors YAP/TAZ. Thermal hyperalgesia and mechanical allodynia were assessed after CCI and pharmacological manipulations through intrathecal administration.

RESULTS

Nerve injury increases spinal level of Aβ1-42, while intrathecal administration of MK-8931 reduces the level of Aβ1-42 and facilitates mechanical allodynia. Intrathecal administration of Aβ1-42 suppresses pain behaviors in the early and late phases of neuropathy. Spinal administration of Aβ1-42 regulates the expression of interleukins, reducing glial activation and phosphorylation of NR2B and ERK1/2 in the spinal cord of CCI rats. Furthermore, intrathecal administration of Aβ1-42 decreases Wnt5b expression and suppresses the nuclear accumulation of YAP and TAZ. Blocking the interaction between Aβ1-42 and Frizzled receptors by cSP5 reverses the analgesic effects of Aβ1-42.

CONCLUSIONS

These findings suggest that spinal Aβ1-42 acts as an endogenous analgesic peptide through regulating cytokines and Wnt pathways. This study may provide a potential target for the development of novel analgesic peptides.

SIGNIFICANCE

This study provides an explanation of reduced pain sensitivity associated with Alzheimer's disease. Furthermore, our findings propose a possible physiological function of beta-amyloid1-42 to regulate pain. This study may provide a potential target for the development of novel analgesics based on an existing endogenous peptide.

Pain processing in older adults with dementia-related cognitive impairment is associated with frontal neurodegeneration

Experimental pain research has shown that pain processing seems to be heightened in dementia. It is unclear which neuropathological changes underlie these alterations. This study examined whether differences in pressure pain sensitivity and endogenous pain inhibition (conditioned pain modulation (CPM)) between individuals with a dementia-related cognitive impairment (N=23) and healthy controls (N=35) are linked to dementia-related neurodegeneration. Pain was assessed via self-report ratings and by analyzing the facial expression of pain using the Facial Action Coding System. We found that cognitively impaired individuals show decreased CPM inhibition as assessed by facial responses compared to healthy controls, which was mediated by decreased gray matter volume in the medial orbitofrontal and anterior cingulate cortex in the patient group. This study confirms previous findings of intensified pain processing in dementia when pain is assessed using non-verbal responses. Our findings suggest that a loss of pain inhibitory functioning caused by structural changes in prefrontal areas might be one of the underlying mechanisms responsible for amplified pain responses in individuals with a dementia-related cognitive impairment.

Neuropathology of the Brainstem to Mechanistically Understand and to Treat Alzheimer's Disease

Alzheimer’s disease (AD) is a devastating neurodegenerative disorder as yet without effective therapy. Symptoms of this disorder typically reflect cortical malfunction with local neurohistopathology, which biased investigators to search for focal triggers and molecular mechanisms. Cortex, however, receives massive afferents from caudal brain structures, which do not only convey specific information but powerfully tune ensemble activity. Moreover, there is evidence that the start of AD is subcortical. The brainstem harbors monoamine systems, which establish a dense innervation in both allo- and neocortex. Monoaminergic synapses can co-release neuropeptides either by precisely terminating on cortical neurons or, when being “en passant”, can instigate local volume transmission. Especially due to its early damage, malfunction of the ascending monoaminergic system emerges as an early sign and possible trigger of AD. This review summarizes the involvement and cascaded impairment of brainstem monoaminergic neurons in AD and discusses cellular mechanisms that lead to their dysfunction. We highlight the significance and therapeutic challenges of transmitter co-release in ascending activating system, describe the role and changes of local connections and distant afferents of brainstem nuclei in AD, and summon the rapidly increasing diagnostic window during the last few years.

Experimentally evoked pain in Alzheimer's disease

BACKGROUND

Pain continues to be underrecognized and undertreated in Alzheimer's disease (AD) while existing guidance about pain assessment and management in dementia is not widespread. Brain regions involved in pain processing and modulation are damaged during AD, and the pain experience in AD is not well understood. Experimental pain studies using psychophysics can further our understanding of the pain experience in AD, which may lead to improved assessment and management of pain in people living with AD.

OBJECTIVE

A systematic review was conducted to explicate the current understanding of experimentally evoked pain in AD from primary research using psychophysical methods.

DATA SOURCES

Peer-reviewed publications were found via PubMed, CINAHL, and PsycINFO. A total of 18 primary research, peer-reviewed full articles that met inclusion criteria were included, representing 929 total participants.

CONCLUSIONS

Experimentally evoked pain in people with AD demonstrates that despite cognitive impairment and a reduced ability to effectively communicate, individuals with AD experience pain similar to or more unpleasant than cognitively intact older adults. This may mean amplified pain unpleasantness in people with AD.

IMPLICATIONS FOR PRACTICE

Our current best practices need to be widely disseminated and put into clinical practice. Self-report of pain continues to be the gold standard, but it is ineffective for noncommunicative patients and those unable to understand pain scales or instructions because of memory/cognitive impairment. Instead, pain treatment should be ethically initiated based on patient reports and behaviors, caregiver/surrogate reports, review of the medical record for painful conditions, analgesic trials, and regular reassessments.

Policy Implications for Pain in Advanced Alzheimer's Disease

Untreated pain in people with Alzheimer's disease continues to be a serious public health problem. Pain is a subjective and complex experience that becomes increasingly challenging to assess as cognition declines. Our understanding of pain processing is incomplete, particularly for special populations such as people living with Alzheimer's disease, and especially in the advanced stages of the disease. Pain-processing networks in the brain are altered in Alzheimer's disease, yet evidence suggests people living with Alzheimer's disease do not experience less pain. Rather, their pain is not adequately recognized or treated. Although scholarly publications provide important assistance, recent widespread reports and guidelines do not include sufficient guidance, especially as Alzheimer's disease progresses to the last stages. Additionally, current pain measurements may not accurately evaluate pain in this condition, and the existing definitions of pain are not adequate when considering the effects of Alzheimer's disease on pain-processing in the brain. There is a need for new, widespread policies, guidelines, and definitions to help clinicians adequately manage pain in people with Alzheimer's disease. These will need to hinge on continued research because it remains unclear how Alzheimer's disease impacts central pain processing, pain expression, and communication of pain. In the meantime, policies and guidelines need to highlight current best practices as well as the fact that pain continues in Alzheimer's disease.

How do patients with Alzheimer's disease imagine their pain?

INTRODUCTION

Pain is underdiagnosed and undertreated in patients with Alzheimer's disease (AD). Pain management is of major importance in this population to limit behavioural and functional consequences. Our study aimed to assess the capacity of AD patients to represent pain using a questionnaire exploring daily painful situations and to determine the most appropriate pain scale assessment.

METHODS

Twenty-eight patients with mild AD, 21 with moderate AD and 28 matched controls underwent the Situation Pain Questionnaire (SP-Q) and assessed imaginary pain with four pain scales. Two scores were compared between the three groups: the P(A) discrimination score and the response bias β score. P(A) reflects the degree of discrimination between high-pain and low-pain events, whereas the β score means the degree to which situations are considered as painful.

RESULTS

Our results showed that AD patients hardly discriminated the high- from low-pain events. Compared to controls, the mean P(A) score was significantly lower for Mild AD (p < 0.03) and Moderate AD (p < 0.004). In addition, the β score indicated that the response bias is higher for AD patients (p < 0.01) in that they overestimated the level of pain.

CONCLUSION

The present results suggest that patients with Mild and Moderate AD are able to recognize and assess an imagined painful situation even though their pain tolerance is lower than that of controls. The pain scales used should be chosen according to the cognitive, sensorial and personal profiles of the patients.

SIGNIFICANCE

The present research is significant because it examines how patients with Alzheimer's disease understand and assess painful situations. Cognitive impairments can modify this ability. Pain is a sensory and subjective experience and to define its feeling can help us in our clinical practice.

The silent epidemic of chronic pain in older adults

Chronic pain is highly prevalent among older adults where it is associated with significant suffering, disability, social isolation, and greater costs and burden to health care systems. Pharmaceutical treatment of chronic pain in older adults is usually only partially effective and is often limited by side effects including urinary retention, constipation, sedation, cognitive impairment, and increased risk of falls. Since older adults are underrepresented in clinical trials testing treatments for chronic pain, the potential impacts of polypharmacy and frailty on reported outcomes and side effect profiles are largely unknown. Thus, for current treatments, providers and patients must balance anticipated benefits of pain reduction with the known and unknown risks of treatment. Chronic pain is also a risk factor for premature death as well as accelerated cognitive decline, suggesting potential shared mechanisms between persistent pain (or its treatment) and dementia. Cognitive decline and dementia may also impact pain perception and the ability to report pain, complicating treatment decisions. Associations between persistent pain and the risks of premature death and accelerated cognitive decline make estimates for chronic pain in these populations particularly challenging. Future research is needed to improve estimates for chronic pain in older adults, to elucidate underlying mechanisms of pain with aging, and to develop and advance safer, more effective treatment options for chronic pain in older adults.

Pain, aging and dementia: Towards a biopsychosocial model

Dementia is a progressive disease associated with irreversible impairment and loss of cognitive abilities. About half of older people with dementia experience pain. In this paper, we propose that pain in older people with dementia can be conceptualized as the final result of the interaction of three heterogeneous phenomena, pain, aging, and dementia, which are created and influenced by the interactions of predisposing, lifelong, and current biopsychosocial factors. We review pain assessment in people with dementia using both self-report and observational/behavioral measures. We then review the biological/sensory, psychological (cognitive and affective) and social dimensions of pain in dementia. The available data suggest that dementia does not impact pain threshold or tolerance. To date, there is little research on the social dimension of pain in dementia. Changes in the affective domain in response to experimental pain have been contradictory with evidence supporting both increased and decreased unpleasantness and emotional responsiveness in people with dementia compared to healthy controls. Clinically, depression is a significant burden for older people with dementia and chronic pain. The relationship between pain and other neuropsychiatric symptoms is controversial, and there is insufficient evidence on which to base conclusions. Some of the most important dementia-related changes may arise in the cognitive domain, including impairments of semantic and episodic memory for pain, executive function, and pain anticipation. Changes in brain activation and interconnectivity support many of these conclusions. Despite methodological limitations, we conclude there are compelling preliminary data to support a biopsychosocial framework of pain and dementia. Future research directions, especially the need for improved assessment tools, are highlighted.

A novel pain assessment tool incorporating automated facial analysis: interrater reliability in advanced dementia

OBJECTIVES

Regardless of its severity, dementia does not negate the experience of pain. Rather, dementia hinders self-reporting mechanisms in affected individuals because they lose the ability to do so. The primary aim of this study was to examine the interrater reliability of the electronic Pain Assessment Tool (ePAT) among raters when assessing pain in residents with moderate-to-severe dementia. Secondly, it sought to examine the relationship between total instrument scores and facial scores, as determined by automated facial expression analysis.

STUDY DESIGN

A 2-week observational study.

SETTING

An accredited, high-care, and dementia-specific residential aged care facility in Perth, Western Australia.

PARTICIPANTS

Subjects were 10 residents (age range: 63.1-84.4 years old) predominantly with severe dementia (Dementia Severity Rating Scale score: 46.3±8.4) rated for pain by 11 aged care staff. Raters (female: 82%; mean age: 44.1±12.6 years) consisted of one clinical nurse, four registered nurses, five enrolled nurses, and one care worker.

MEASUREMENTS

ePAT measured pain using automated detection of facial action codes and recordings of pain behaviors.

RESULTS

A total of 76 assessments (rest =38 [n=19 pairs], movement =38 [n=19 pairs]) were conducted. At rest, raters' agreement was excellent on overall total scores (coefficient of concordance =0.92 [95% CI: 0.85-0.96]) and broad category scores (κ=1.0). Agreement was moderate (κ=0.59) on categorical scores upon movement, while it was exact in 68.4% of the cases. Agreement in actual pain category scores gave κw=0.72 (95% CI: 0.58-0.86) at rest and κw=0.69 (95% CI: 0.50-0.87) with movement. All raters scored residents with higher total scores post-mobilization compared to rest. More facial action unit codes were also detected during pain (mean: 2.5 vs 1.9; p<0.0012) and following mobilization (mean: 2.5 vs 1.7; p<0.0001) compared to no pain and rest, respectively.

CONCLUSIONS

ePAT, which combines automated facial expression analysis and clinical behavioral indicators in a single observational pain assessment tool, demonstrates good reliability properties, which supports its appropriateness for use in residents with advanced dementia.

Revealing brain mechanisms of mTOR-mediated translational regulation: Implications for chronic pain

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mTOR is a major regulator of protein translation.

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mTOR serves an important role in neural plasticity.

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mTOR signalling in the brain as a pathology for neurological disorder is known.

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mTOR signalling in the brain as a chronic pain mechanism is understudied.

In the spinal cord, altered protein transcription and translation have received a lot of recent attention for their role in neural plasticity, a major mechanism leading to the development of chronic pain. However, changes in brain plasticity are also associated with the maintenance of pain symptoms, but these cellular mechanisms remain less clear. The mechanistic/mammalian target of rapamycin (mTOR) is a master regulator of protein synthesis, and controls several neuronal functions, including neural plasticity. While aberrant changes in mTOR signaling are associated with sensitization of the pain pathway (sensory neurons and spinal cord), there are various nervous system diseases that have pain as a comorbidity and altered mTOR activity in the brain. Here, we provide a brief review of mTOR changes in the brain that are associated with some neurological disorders and focus on how these changes may be relevant to the pain of the underlying condition and chronic pain itself.

Altered Behavioral and Autonomic Pain Responses in Alzheimer's Disease Are Associated with Dysfunctional Affective, Self-Reflective and Salience Network Resting-State Connectivity

While pain behaviors are increased in Alzheimer's disease (AD) patients compared to healthy seniors (HS) across multiple disease stages, autonomic responses are reduced with advancing AD. To better understand the neural mechanisms underlying these phenomena, we undertook a controlled cross-sectional study examining behavioral (Pain Assessment in Advanced Dementia, PAINAD scores) and autonomic (heart rate, HR) pain responses in 24 HS and 20 AD subjects using acute pressure stimuli. Resting-state fMRI was utilized to investigate how group connectivity differences were related to altered pain responses. Pain behaviors (slope of PAINAD score change and mean PAINAD score) were increased in patients vs.

CONTROLS

Autonomic measures (HR change intercept and mean HR change) were reduced in severe vs. mildly affected AD patients. Group functional connectivity differences associated with greater pain behavior reactivity in patients included: connectivity within a temporal limbic network (TLN) and between the TLN and ventromedial prefrontal cortex (vmPFC); between default mode network (DMN) subcomponents; between the DMN and ventral salience network (vSN). Reduced HR responses within the AD group were associated with connectivity changes within the DMN and vSN-specifically the precuneus and vmPFC. Discriminant classification indicated HR-related connectivity within the vSN to the vmPFC best distinguished AD severity. Thus, altered behavioral and autonomic pain responses in AD reflects dysfunction of networks and structures subserving affective, self-reflective, salience and autonomic regulation.

The Impact of Alzheimer's Disease on the Resting State Functional Connectivity of Brain Regions Modulating Pain: A Cross Sectional Study

BACKGROUND

It is currently unknown why people with Alzheimer's disease (AD) receive less pain medication and report pain less frequently.

OBJECTIVE

The purpose of this study was to determine the impact of AD on thermal psychophysics and resting-state functional connectivity (RSFC) among sensory, affective, descending modulatory, and default mode structures.

METHODS

Controls (n = 23, 13 = female) and age-matched people with AD (n = 23, 13 = females) underwent psychophysical testing to rate perceptions of warmth, mild, and moderate pain and then completed resting-state fMRI. Between groups analysis in psychophysics and RSFC were conducted among pre-defined regions of interest implicated in sensory and affective dimensions of pain, descending pain modulation, and the default mode network.

RESULTS

People with AD displayed higher thermal thresholds for warmth and mild pain but similar moderate pain thresholds to controls. No between-group differences were found for unpleasantness at any percept. Relative to controls, people with AD demonstrated reduced RSFC between the right posterior insula and left anterior cingulate and also between right amygdala and right secondary somatosensory cortex. Moderate pain unpleasantness reports were associated with increased RSFC between right dorsolateral prefrontal cortex and left ACC in controls only.

CONCLUSIONS

While AD had little effect on unpleasantness, people with AD had increased thermal thresholds, altered RSFC, and no association of psychophysics with RSFC in pain regions. Findings begin to elucidate that in people with AD, altered integration of pain sensation, affect, and descending modulation may, in part, contribute to decreased verbal pain reports and thus decreased analgesic administration.

Pain in Neurodegenerative Disease: Current Knowledge and Future Perspectives

Neurodegenerative diseases are going to increase as the life expectancy is getting longer. The management of neurodegenerative diseases such as Alzheimer's disease (AD) and other dementias, Parkinson's disease (PD) and PD related disorders, motor neuron diseases (MND), Huntington's disease (HD), spinocerebellar ataxia (SCA), and spinal muscular atrophy (SMA), is mainly addressed to motor and cognitive impairment, with special care to vital functions as breathing and feeding. Many of these patients complain of painful symptoms though their origin is variable, and their presence is frequently not considered in the treatment guidelines, leaving their management to the decision of the clinicians alone. However, studies focusing on pain frequency in such disorders suggest a high prevalence of pain in selected populations from 38 to 75% in AD, 40% to 86% in PD, and 19 to 85% in MND. The methods of pain assessment vary between studies so the type of pain has been rarely reported. However, a prevalent nonneuropathic origin of pain emerged for MND and PD. In AD, no data on pain features are available. No controlled therapeutic trials and guidelines are currently available. Given the relevance of pain in neurodegenerative disorders, the comprehensive understanding of mechanisms and predisposing factors, the application and validation of specific scales, and new specific therapeutic trials are needed.

Contact heat sensitivity and reports of unpleasantness in communicative people with mild to moderate cognitive impairment in Alzheimer's disease: a cross-sectional study

BACKGROUND

Compared to healthy controls, people with Alzheimer's disease (AD) have been shown to receive less pain medication and report pain less frequently. It is unknown if these findings reflect less perceived pain in AD, an inability to recognize pain, or an inability to communicate pain.

METHODS

To further examine aspects of pain processing in AD, we conducted a cross-sectional study of sex-matched adults ≥65 years old with and without AD (AD: n = 40, female = 20, median age = 75; control: n = 40, female = 20, median age = 70) to compare the psychophysical response to contact-evoked perceptual heat thresholds of warmth, mild pain, and moderate pain, and self-reported unpleasantness for each percept.

RESULTS

When compared to controls, participants with AD required higher temperatures to report sensing warmth (Cohen's d = 0.64, p = 0.002), mild pain (Cohen's d = 0.51, p = 0.016), and moderate pain (Cohen's d = 0.45, p = 0.043). Conversely, there were no significant between-group differences in unpleasantness ratings (p > 0.05).

CONCLUSIONS

The between-group findings demonstrate that when compared to controls, people with AD are less sensitive to the detection of thermal pain but do not differ in affective response to the unpleasant aspects of thermal pain. These findings suggest that people with AD may experience greater levels of pain and potentially greater levels of tissue or organ damage prior to identifying and reporting injury. This finding may help to explain the decreased frequency of pain reports and consequently a lower administration of analgesics in AD.

Loss in Executive Functioning Best Explains Changes in Pain Responsiveness in Patients with Dementia-Related Cognitive Decline

There is ample evidence that dementia changes the processing of pain. However, it is not known whether this change in pain processing is related to the general decline in cognitive functioning or whether it may be related to specific domains of cognitive functioning. With the present study we tried to answer this question. We assessed different cognitive domains (orientation, memory, abstract thinking/executive function, aphasia and apraxia, and information processing speed) in 70 older patients with cognitive impairment (mild cognitive impairment up to moderate degrees of dementia). Pain responsiveness was assessed by measuring the nociceptive flexion reflex (NFR) threshold and facial responses to noxious electrical stimulation. Using regression analyses, we assessed which domain of cognitive functioning best predicted variance in pain responsiveness. Variance in pain responsiveness (NFR and facial expressions) was best explained by those items assessing executive functioning even when controlling for overall cognitive performance and memory functioning. The close association between executive functioning and pain responsiveness suggests that dementia-related neurodegeneration in prefrontal areas might result not only in reduced executive functioning but also in a loss of pain inhibitory potency, rendering the patient more vulnerable to pain. Our findings also suggest that pain assessment in dementia should be regularly completed by tests of cognitive functions.

Pain and temperature processing in dementia: a clinical and neuroanatomical analysis

Symptoms suggesting altered pain and temperature processing have been described in dementia diseases. Using a semi-structured caregiver questionnaire and MRI voxel-based morphometry in patients with frontotemporal degeneration or Alzheimer’s disease, Fletcher et al. show that these symptoms are underpinned by atrophy in a distributed thalamo-temporo-insular network implicated in somatosensory processing.

Symptoms suggesting altered processing of pain and temperature have been described in dementia diseases and may contribute importantly to clinical phenotypes, particularly in the frontotemporal lobar degeneration spectrum, but the basis for these symptoms has not been characterized in detail. Here we analysed pain and temperature symptoms using a semi-structured caregiver questionnaire recording altered behavioural responsiveness to pain or temperature for a cohort of patients with frontotemporal lobar degeneration (n = 58, 25 female, aged 52–84 years, representing the major clinical syndromes and representative pathogenic mutations in the C9orf72 and MAPT genes) and a comparison cohort of patients with amnestic Alzheimer’s disease (n = 20, eight female, aged 53–74 years). Neuroanatomical associations were assessed using blinded visual rating and voxel-based morphometry of patients’ brain magnetic resonance images. Certain syndromic signatures were identified: pain and temperature symptoms were particularly prevalent in behavioural variant frontotemporal dementia (71% of cases) and semantic dementia (65% of cases) and in association with C9orf72 mutations (6/6 cases), but also developed in Alzheimer’s disease (45% of cases) and progressive non-fluent aphasia (25% of cases). While altered temperature responsiveness was more common than altered pain responsiveness across syndromes, blunted responsiveness to pain and temperature was particularly associated with behavioural variant frontotemporal dementia (40% of symptomatic cases) and heightened responsiveness with semantic dementia (73% of symptomatic cases) and Alzheimer’s disease (78% of symptomatic cases). In the voxel-based morphometry analysis of the frontotemporal lobar degeneration cohort, pain and temperature symptoms were associated with grey matter loss in a right-lateralized network including insula (P < 0.05 corrected for multiple voxel-wise comparisons within the prespecified anatomical region of interest) and anterior temporal cortex (P < 0.001 uncorrected over whole brain) previously implicated in processing homeostatic signals. Pain and temperature symptoms accompanying C9orf72 mutations were specifically associated with posterior thalamic atrophy (P < 0.05 corrected for multiple voxel-wise comparisons within the prespecified anatomical region of interest). Together the findings suggest candidate cognitive and neuroanatomical bases for these salient but under-appreciated phenotypic features of the dementias, with wider implications for the homeostatic pathophysiology and clinical management of neurodegenerative diseases.

Fibromyalgia syndrome and cognitive dysfunction in elderly: a case series

AIM

Fibromyalgia syndrome (FMS) is an extremely rare complication of neurocognitive disorders (NCDs). We experienced seven such cases, and we discuss their clinical manifestation and pathomechanisms.

METHODS

Seven patients with FMS as a complication of NCD were enrolled. We used the patients' medical records to identify clinical manifestations and obtain experimental data, such as pain questionnaire scores, cognitive tests, genetics and radiological imaging of the brain.

RESULTS

The seven patients were clinically diagnosed with frontotemporal NCD (n = 3) or Alzheimer's disease (n = 4). No patient presented with any organic disorder that would explain their chronic pain. Through their courses, they experienced refractory widespread pain continuously despite analgesics. Brain magnetic resonance imaging revealed moderate or severe atrophic changes in the temporal lobes and hippocampus. Three-dimensional stereotactic surface projection (3D-SSP) analysis of brain single photon emission computed tomography (SPECT), indicated severe hypoperfusion on the right side of the medial temporal lobe, both sides of the anterior corpus callosum, anterior cingulate gyrus, and primary sensory area. Genetic analysis uncovered no pathogenic mutations.

CONCLUSIONS

Neurodegenerative disorders are rarely complicated by FMS, which is associated with relatively severe pain. Central sensitization may be a possible risk factor of widespread pain in elderly patients with NCD.

An international road map to improve pain assessment in people with impaired cognition: the development of the Pain Assessment in Impaired Cognition (PAIC) meta-tool

Background

Pain is common in people with dementia, yet identification is challenging. A number of pain assessment tools exist, utilizing observation of pain-related behaviours, vocalizations and facial expressions. Whilst they have been developed robustly, these often lack sufficient evidence of psychometric properties, like reliability, face and construct validity, responsiveness and usability, and are not internationally implemented. The EU-COST initiative “Pain in impaired cognition, especially dementia” aims to combine the expertise of clinicians and researchers to address this important issue by building on previous research in the area, identifying existing pain assessment tools for dementia, and developing consensus for items for a new universal meta-tool for use in research and clinical settings. This paper reports on the initial phase of this collaboration task.

Methods

All existing observational pain behaviour tools were identified and elements categorised using a three-step reduction process. Selection and refinement of items for the draft Pain Assessment in Impaired Cognition (PAIC) meta-tool was achieved through scrutiny of the evidence, consensus of expert opinion, frequency of use and alignment with the American Geriatric Society guidelines. The main aim of this process was to identify key items with potential empirical, rather than theoretical value to take forward for testing.

Results

12 eligible assessment tools were identified, and pain items categorised according to behaviour, facial expression and vocalisation according to the AGS guidelines (Domains 1 – 3). This has been refined to create the PAIC meta-tool for validation and further refinement. A decision was made to create a supporting comprehensive toolkit to support the core assessment tool to provide additional resources for the assessment of overlapping symptoms in dementia, including AGS domains four to six, identification of specific types of pain and assessment of duration and location of pain.

Conclusions

This multidisciplinary, cross-cultural initiative has created a draft meta-tool for capturing pain behaviour to be used across languages and culture, based on the most promising items used in existing tools. The draft PAIC meta-tool will now be taken forward for evaluation according to COSMIN guidelines and the EU-COST protocol in order to exclude invalid items, refine included items and optimise the meta-tool.

Electronic supplementary material

The online version of this article (doi:10.1186/s12883-014-0229-5) contains supplementary material, which is available to authorized users.

Silent and suffering: a pilot study exploring gaps between theory and practice in pain management for people with severe dementia in residential aged care facilities

Background

Pain is common in older people, particularly those in residential aged care facilities (RACF) and those with dementia. However, despite 20 years of discourse on pain and dementia, pain is still undetected or misinterpreted in people with dementia in residential aged care facilities, particularly those with communication difficulties.

Methods

A topical survey typology with semistructured interviews was used to gather attitudes and experiences of staff from 15 RACF across Northern Sydney Local Health District.

Results

While pain is proactively assessed and pain charts are used in RACF, this is more often regulatory-driven than patient-driven (eg, prior to accreditation). Identification of pain and need for pain relief was ill defined and poorly understood. Both pharmacological and non-pharmacological regimes were used, but in an ad hoc, variable and unsystematic manner, with patient, staff, and attitudinal obstacles between the experience of pain and its relief.

Conclusion

A laborious “pain communication chain” exists between the experience of pain and its relief for people with severe dementia within RACF. Given the salience of pain for older people with dementia, we recommend early, proactive consideration and management of pain in the approach to behaviors of concern. Individualized pain measures for such residents; empowerment of nursing staff as “needs interpreters”; collaborative partnerships with common care goals between patients where possible; RACF staff, doctors, and family carers; and more meaningful use of pain charts to map response to stepped pain protocols may be useful strategies to explore in clinical settings.

Outcome Measures for Dementia in the Advanced Stage and at the End of Life

Increasing life span and lack of medication for prevention or treatment of progressive dementias will significantly increase the number of individuals with advanced dementia worldwide. Providing optimal care for them will stretch health care resources and will require evaluation of different treatment strategies. This paper is presenting measures that may be used in this patient population. Evaluation of global goals of palliative care may include measuring quality of life by QUALID scale, comfort by DS-DAT scale, and engagement by MPES scale. Symptom control may be achieved by measuring pain by PAINAD or PACSLAC scales, by evaluating behavioral symptoms and their management (agitation by SOAPD scale, apathy by AES scale and rejection of care by RTC-DAT scale), and by monitoring patients for dyspnea using RDOS scale. Outcomes of palliative care at the end of life may be evaluated by EOLD-CAD scale and by determining family satisfaction with care (EOLD-SWC). Items included in these scales, psychometric properties, and research use of these scales are described. It is hoped that information in this paper will stimulate research interest in this important area.

Systems-Level G Protein-Coupled Receptor Therapy Across a Neurodegenerative Continuum by the GLP-1 Receptor System

With our increasing appreciation of the true complexity of diseases and pathophysiologies, it is clear that this knowledge needs to inform the future development of pharmacotherapeutics. For many disorders, the disease mechanism itself is a complex process spanning multiple signaling networks, tissues, and organ systems. Identifying the precise nature and locations of the pathophysiology is crucial for the creation of systemically effective drugs. Diseases once considered constrained to a limited range of organ systems, e.g., central neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington' disease (HD), the role of multiple central and peripheral organ systems in the etiology of such diseases is now widely accepted. With this knowledge, it is increasingly clear that these seemingly distinct neurodegenerative disorders (AD, PD, and HD) possess multiple pathophysiological similarities thereby demonstrating an inter-related continuum of disease-related molecular alterations. With this systems-level appreciation of neurodegenerative diseases, it is now imperative to consider that pharmacotherapeutics should be developed specifically to address the systemic imbalances that create the disorders. Identification of potential systems-level signaling axes may facilitate the generation of therapeutic agents with synergistic remedial activity across multiple tissues, organ systems, and even diseases. Here, we discuss the potentially therapeutic systems-level interaction of the glucagon-like peptide 1 (GLP-1) ligand-receptor axis with multiple aspects of the AD, PD, and HD neurodegenerative continuum.

Pain management in patients with dementia

There are an estimated 35 million people with dementia across the world, of whom 50% experience regular pain. Despite this, current assessment and treatment of pain in this patient group are inadequate. In addition to the discomfort and distress caused by pain, it is frequently the underlying cause of behavioral symptoms, which can lead to inappropriate treatment with antipsychotic medications. Pain also contributes to further complications in treatment and care. This review explores four key perspectives of pain management in dementia and makes recommendations for practice and research. The first perspective discussed is the considerable uncertainty within the literature on the impact of dementia neuropathology on pain perception and processing in Alzheimer's disease and other dementias, where white matter lesions and brain atrophy appear to influence the neurobiology of pain. The second perspective considers the assessment of pain in dementia. This is challenging, particularly because of the limited capacity of self-report by these individuals, which means that assessment relies in large part on observational methods. A number of tools are available but the psychometric quality and clinical utility of these are uncertain. The evidence for efficient treatment (the third perspective) with analgesics is also limited, with few statistically well-powered trials. The most promising evidence supports the use of stepped treatment approaches, and indicates the benefit of pain and behavioral interventions on both these important symptoms. The fourth perspective debates further difficulties in pain management due to the lack of sufficient training and education for health care professionals at all levels, where evidence-based guidance is urgently needed. To address the current inadequate management of pain in dementia, a comprehensive approach is needed. This would include an accurate, validated assessment tool that is sensitive to different types of pain and therapeutic effects, supported by better training and support for care staff across all settings.

Pain reports and pain medication treatment in nursing home residents with and without dementia

AIM

The purpose of this pilot study was to determine if a diagnosis of dementia influenced pain self-reports and pain medication use in a group of verbally communicative nursing home (NH) residents.

METHODS

The study design was a between groups, cross-sectional chart audit and a seven-question structured pain interview comparing outcomes in residents with and without a diagnosis of dementia. The study was carried out at a large metropolitan NH in the southern USA. The participants consisted of 52 long-stay NH residents capable of self-consent with at least one order for pain medication (opioid or non-narcotic) either pro re nata, scheduled or both. Approximately 40% (n = 20) had a diagnosis of dementia.

RESULTS

Although each group had similar pain-related diagnoses, residents without a dementia diagnosis were significantly more likely to have a medication order for an opioid (OR 4.37,95% CI 1.29-14.73, P = 0.018). Based on self-reported pain interview responses, no statistically significant differences were identified between the groups for chronic pain symptoms. However, among residents who reported current pain, those with a dementia diagnosis reported greater pain intensity (based on a 0-10 numeric rating scale) than did those without dementia (median 8.0 vs 6.0, respectively; P = 0.010).

CONCLUSIONS

Verbally communicative NH residents with mild and moderate cognitive impairment can report their pain symptoms and pain intensity. Nurses in long-term care might assume that residents with dementia cannot reliably self-report their pain; however, suffering from untreated severe pain could exacerbate cognitive impairment, worsen functional impairment and severely impair sleep. A brief, focused pain interview might be one method for increasing the detection of moderate to severe pain in verbally communicative NH residents with dementia.

Non-cognitive symptoms and related conditions in the Alzheimer's disease: a literature review

The Alzheimer's disease is considered a progressive cognitive disorder; however, several non-cognitive symptoms accompany all stages of the disease, appearing at times before the cognitive symptoms become manifest. This article reviews the literature on non-cognitive symptoms normally related to the Alzheimer's disease, including gait and balance dysfunction, olfactory dysfunction, diabetes, pain, and psychiatric symptoms.

Pain in people with Alzheimer disease: potential applications for psychophysical and neurophysiological research

Pain management in people with dementia is a critical problem. Recently, psychophysical and neuroimaging techniques have been used to extend our understanding of pain processing in the brain as well as to identify structural and functional changes in Alzheimer disease (AD). But interpreting the complex relationship between AD pathology, brain activation, and pain reports is challenging. This review proposes a conceptual framework for designing and interpreting psychophysical and neuroimaging studies of pain processing in people with AD. Previous human studies describe the lateral (sensory) and medial (affective) pain networks. Although the majority of the literature on pain supports the lateral and medial networks, some evidence supports an additional rostral pain network, which is believed to function in the production of pain behaviors. The sensory perception of pain as assessed through verbal report and behavioral display may be altered in AD. In addition, neural circuits mediating pain perception and behavioral expression may be hyperactive or underactive, depending on the brain region involved, stage of the disease, and type of pain (acute experimental stimuli or chronic medical conditions). People with worsening AD may therefore experience pain but be unable to indicate pain through verbal or behavioral reports, leaving them at great risk of experiencing untreated pain. Psychophysical (verbal or behavioral) and neurophysiological (brain activation) approaches can potentially address gaps in our knowledge of pain processing in AD by revealing the relationship between neural processes and verbal and behavioral outcomes in the presence of acute or chronic pain.

Assessment and treatment of pain in people with dementia

Many elderly people experience pain and regularly take analgesic medication. Pain is also frequent in people with dementia, particularly those with severe disease. As no robust clinical guidelines are available for the treatment of pain in the context of dementia, the risk of inadequate treatment in individuals with this condition is high. Furthermore, our understanding of the aetiology of pain and the potential role of dementia-associated neuropathology in pain is limited. These issues are important in the clinical management of individuals with dementia, as untreated pain is a major contributor to reduced quality of life and disability, and can lead to increased behavioural and psychological symptoms. Assessment scales to identify pain in people with dementia have been highlighted in recent studies, but there is little evidence for consistency between these tools. Numerous studies have evaluated various approaches for the treatment of pain, including stepped-care protocols and/or administration of paracetamol and opioid medications. In this Review, we summarize the best-available evidence regarding the aetiology, assessment and treatment of pain in people with dementia. Further validation of assessment tools and large-scale trials of treatment approaches in people with dementia are needed to improve clinical guidance for the treatment of pain in these individuals.