Miriam Kunz

Influence of dementia on multiple components of pain

Experimental findings on the influence of dementia on pain have so far been conflicting. There is evidence for a decreased, an unchanged and even for an increased pain processing in patients with dementia. The present study was conducted to add on the description of the impact of dementia on pain processing by assessing multiple components of pain (subjective, facial, motor reflex and autonomic responses) in parallel in one group of demented patients.

The effects of DNIC-type inhibition on temporal summation compared to single pulse processing: Does sex matter?

Abstract A few experimental observations have suggested that diffuse noxious inhibitory control (DNIC)‐type inhibition acts preferentially on the pain system if this is in a sensitised state, e.g. after slow temporal summation (wind‐up). However, firm evidence is still missing. Furthermore, sex‐related factors, which seem to affect temporal summation as well as DNIC effects, might thus also modulate the interaction of these two processes. To answer these questions, we investigated 40 young and pain‐free subjects (20 female and 20 male). The conditioning stimulus in our DNIC paradigm was realized by immersion of the hand into a water tub containing either 42 °C (non‐painful heat) or 46 °C (painful heat) hot water. The test stimuli were either single pulses or series of five pulses (0.5 Hz repetition frequency) produced by a pressure algometer. The VAS ratings for the last stimulus in the series were significantly higher than for the single pulse (temporal summation). The ratings were significantly reduced by the 42 °C conditioning stimulus and even more by the 46 °C conditioning stimulus, suggesting DNIC‐like inhibition. This was equally true both for the single pulse and for the series of pulses. Sex differences were not observed for temporal summation, DNIC inhibition or for the interaction of the two processes, although women exhibited significantly lower pressure pain thresholds and higher ratings for the tonic heat stimuli. In conclusion, DNIC‐type inhibition apparently does not preferentially act on a sensitised pain system after slow temporal summation. Considering the sex of the subjects does not change this insight.

Are both the sensory and the affective dimensions of pain encoded in the face

Summary The facial expression of pain is a multidimensional response system that differentially encodes affective and sensory pain qualities. Abstract The facial expression of pain plays a crucial role in pain communication and pain diagnostics. Despite its importance, it has remained unknown which dimensions of pain (sensory and/or affective) are encoded in the face. To answer this question, we used a well‐established cognitive strategy (suggestions) to differentially modulate the sensory and affective dimensions of pain and investigate the effect of this manipulation on facial responses to experimental pain. Twenty‐two subjects participated in the study. Their facial expressions, pain intensity, and unpleasantness ratings as well as skin conductance responses to tonic and phasic heat pain were assessed before and after suggestions directed toward increase in affective and sensory qualities of pain, respectively, were provided. Facial expressions were analyzed with the Facial Action Coding system. As expected, suggestions designed to increase the sensory dimension produced a selective increase in pain intensity ratings, whereas suggestions designed to increase pain affect produced increased unpleasantness ratings and elevated skin conductance responses. Furthermore, suggestions for either increased pain affect or pain sensation produced selective modulations in facial response patterns, with facial movements around the eyes mostly encoding sensory aspects, whereas movements of the eyebrows and of the upper lip were closely associated with the affective pain dimension. The facial expression of pain is a multidimensional response system that differentially encodes affective and sensory pain qualities. This differential encoding might have evolved to guarantee that the specific characteristics of one’s pain experience are facially communicated, thereby ensuring adequate help and support from others.

Pain monitoring: A dynamic and context-sensitive system

The current paper presents an automatic and context sensitive system for the dynamic recognition of pain expression among the six basic facial expressions and neutral on acted and spontaneous sequences. A machine learning approach based on the Transferable Belief Model, successfully used previously to categorize the six basic facial expressions in static images [2,61], is extended in the current paper for the automatic and dynamic recognition of pain expression from video sequences in a hospital context application. The originality of the proposed method is the use of the dynamic information for the recognition of pain expression and the combination of different sensors, permanent facial features behavior, transient features behavior, and the context of the study, using the same fusion model. Experimental results, on 2-alternative forced choices and, for the first time, on 8-alternative forced choices (i.e. pain expression is classified among seven other facial expressions), show good classification rates even in the case of spontaneous pain sequences. The mean classification rates on acted and spontaneous data reach 81.2% and 84.5% for the 2-alternative and 8-alternative forced choices, respectively. Moreover, the system performances compare favorably to the human observer rates (76%), and lead to the same doubt states in the case of blend expressions.

The relation between catastrophizing and facial responsiveness to pain.

Abstract Pain catastrophizing has recently been suggested to have a social function based on a positive association observed with facial responsiveness to noxious stimulation. However, this assumption is based on studies applying nociceptive stimuli of fixed intensity, such that high catastrophizers not only displayed increased pain behavior but also rated the stimulation as being more painful. The aim of this study was to investigate the relation between catastrophizing and facial responsiveness while controlling for individual differences in pain sensitivity. The facial expression of pain was investigated in 44 young and pain‐free individuals in response to painful and non‐painful phasic heat stimuli. Painful temperatures were tailored to the individual sensitivity to produce moderate pain. Facial responses were videotaped and objectively examined using the Facial Action Coding System. We also assessed skin conductance activity as an autonomic indicator of pain‐related responses. Catastrophizing was assessed using the Pain Catastrophizing Scale (PCS). In accordance with previous findings, subjects scoring higher on pain catastrophizing required lower thermal intensities to induce a moderately painful sensation (r = −0.40, p = 0.007). However, catastrophizing did not correlate with facial responsiveness to perceptually controlled painful stimulation (r = −0.02, p = 0.88). Moreover, correlation analyses revealed no significant associations between catastrophizing and skin conductance responses. The present findings provide further support for the impact of pain catastophizing on pain sensitivity. However, our finding of no relation between catastrophizing and facial responsiveness when participants are experiencing comparable psychophysical pain intensities, challenges previous assumptions that high catastrophizers display amplified pain behavior; at least in young and pain‐free individuals.

Modulation of electrically induced pain by paired pulse transcranial magnetic stimulation of the medial frontal cortex

OBJECTIVEnAim of this study was to investigate whether paired pulse transcranial magnetic stimulation (ppTMS) applied over the medial frontal cortex (MFC) affects acute Adelta fiber-mediated electrically induced pain. In addition, we investigated whether this effect depends on the time course of the stimulation, on the noxious stimulus intensity or on the ppTMS intensity.nnnMETHODSnFor painful stimulation, the electrical stimulus for the nociceptive flexion reflex (NFR) was used. PpTMS (ISI: 50 ms) was applied over the medial frontal cortex at different intervals ranging from 0 to 1,000 ms following the previous elicited NFR in 10 healthy volunteers. Three sequences at 3 different NFR stimulus intensities (at NFR threshold, 1.3 x and 1.6 x NFR threshold) with a ppTMS stimulus intensity at 1.2 x resting motor threshold (RMT) and one sequence with elevated ppTMS at 1.6 x RMT stimulus intensity were performed. Pain intensity and pain unpleasantness were assessed by visual analogue scales.nnnRESULTSnPain ratings differed in dependence of the interstimulus interval between NFR and ppTMS. Post-hoc t-tests revealed an increased verbal pain report within interstimulus intervals from 25 to 75 ms at NFR threshold as well as for 25 ms at 1.3 x NFR threshold when ppTMS was applied at 1.2 x RMT and from 0 to 75 ms at 1.6 x NFR threshold when ppTMS was applied at 1.6 x RMT.nnnCONCLUSIONSnThe present data suggest that ppTMS over MFC-applied in a certain time window-can enhance pain perception of acute Adelta fiber-mediated electrically induced pain. We hypothesize that the increase of pain is due to interference between ppTMS and the incoming nociceptive input. Further pain processing might be modulated by direct effects on MFC or indirect effects on anterior cingulate cortex (ACC) or spinal nociception.nnnSIGNIFICANCEnBrain areas involved in cognitive and emotional adaptation to pain can be used, in place of primary motor areas, as cortical targets in TMS trials of experimental or ongoing pain.

Effects of ageing on spinal motor and autonomic pain responses

The course of ageing leads to various changes in the nervous system, which can affect pain processing in the elderly. However, the affection of different components of the nociceptive system remains unclear. To investigate basic nocifensive responses, we compared age-related changes of autonomic and motor reflex responses to noxious electrical stimulation. In 39 healthy young subjects (mean +/- S.D.; 24.1 +/- 3.3 years) and 52 healthy elderly subjects (mean +/- S.D.; 71.9 +/- 5.3 years) the nociceptive flexion reflex (NFR) and the sympathetic skin response (SSR) were determined using noxious electrical stimulation of the sural nerve. Verbal pain ratings were assessed in addition. No ageing effects on the NFR and on verbal pain ratings were found, whereas the SSR amplitude declined significantly with ageing. Since both SSR and NFR share comparable primary afferent pathways and the motor as well as the subjective responses to noxious stimulation were preserved, our data seem to suggest that central or peripheral efferent sympathetic functions are altered by age.

Mehrdimensionale Schmerzmessung bei Demenzpatienten

BACKGROUNDnIt is well known that patients with dementia complain less about pain and receive fewer analgesics than other patients. The question arises of whether disorders associated with dementia change the processing of pain.nnnMETHODSnA total of 20 patients with dementia and 40 patients with mild cognitive impairment (MCI) as well as 40 healthy control subjects were investigated for their subjective (category scale), facial (FACS) and motor (R-III reflex) pain responses to mechanical and electrical stimuli.nnnRESULTSnPatients with dementia did not rate the intensity of the stimuli differently; however, they were less frequently capable of providing ratings. At equal levels of stimulus intensity, demented patients showed stronger facial responses. The R-III reflex thresholds were lowered in demented patients. MCI patients appeared only slightly changed.nnnCONCLUSIONSnOur findings suggest that the processing of acute noxious stimuli is intensified in patients with dementia. Against the background of a reduced prescription of analgesics, an under-treatment of pain in patients with dementia might be the consequence.ZusammenfassungHintergrundEs ist bekannt, dass Demenzpatienten weniger Schmerzmittel erhalten und weniger über Schmerzen klagen als kognitiv Gesunde. Hieraus ergibt sich die Frage, ob Demenzerkrankungen die Schmerzverarbeitung verändern.MethodenAn 20xa0Patienten mit Demenz und 40 mit leichter kognitiver Beeinträchtigung (LKB) sowie 40 Kontrollpersonen wurden die verbalen (Kategorialskala), mimischen (FACS) und motorischen Schmerzreaktionen (R-III-Reflex) auf mechanische und elektrische Reize erfasst.ErgebnisseDemenzpatienten schätzten die Stärke der Schmerzreize nicht anders ein, waren jedoch seltener hierzu in der Lage. Bei gleich starken Reizen reagierten die Demenzpatienten mimisch stärker; die Schwelle ihres R-III-Reflexes war vermindert. LKB-Patienten erwiesen sich in allen Schmerzparametern nur tendenziell verändert.SchlussfolgerungUnsere Daten weisen daraufhin, dass die Verarbeitung akuter nozizeptiver Reize bei Demenzpatienten verstärkt ist. Vor dem Hintergrund der selteneren Analgetikaverordnung könnte dies auf eine schmerztherapeutische Unterversorgung von Demenzpatienten hindeuten.AbstractBackgroundIt is well known that patients with dementia complain less about pain and receive fewer analgesics than other patients. The question arises of whether disorders associated with dementia change the processing of pain.MethodsA total of 20xa0patients with dementia and 40xa0patients with mild cognitive impairment (MCI) as well as 40 healthy control subjects were investigated for their subjective (category scale), facial (FACS) and motor (R-III reflex) pain responses to mechanical and electrical stimuli.ResultsPatients with dementia did not rate the intensity of the stimuli differently; however, they were less frequently capable of providing ratings. At equal levels of stimulus intensity, demented patients showed stronger facial responses. The R-III reflex thresholds were lowered in demented patients. MCI patients appeared only slightly changed.ConclusionsOur findings suggest that the processing of acute noxious stimuli is intensified in patients with dementia. Against the background of a reduced prescription of analgesics, an under-treatment of pain in patients with dementia might be the consequence.

Veränderung des Schmerzerlebens bei Alzheimer-Patienten

Zusammenfassung: Klinische Studien, die nahe legen, dass Alzheimer-Patienten im Vergleich zur Altersgruppe deutlich seltener uber Schmerzen berichten und deutlich weniger Analgetika verschrieben bekommen, haben die Frage aufgeworfen, inwieweit die Alzheimer-Erkrankung zu Veranderungen im Schmerzerleben fuhrt. Um diese Frage zu beantworten, sind experimentelle Studien unabdingbar, da nur sie erlauben, Veranderungen des Schmerzsystems selbst zu erfassen. Die bisherigen experimentellen Befunde weisen darauf hin, dass die Schmerztoleranzschwelle deutlich erhoht und die vegetative Schmerzreaktion teilweise erheblich vermindert ist. Die Schmerzschwelle und schmerzkorrelierten Hirnpotenziale zeigten sich hingegen weitestgehend unverandert. Dies sprache eher fur eine Abschwachung der Schmerzreagibilitat bei Alzheimer-Demenz. Als mogliche Erklarungen hierfur diskutieren wir altersbedingte Veranderungen des Schmerzerlebens und neuroanatomische Veranderungen im Rahmen der Alzheimer-Erkrankung. Erste Ergebnisse einer...

Multidimensional pain assessment in patients with dementia

BACKGROUNDnIt is well known that patients with dementia complain less about pain and receive fewer analgesics than other patients. The question arises of whether disorders associated with dementia change the processing of pain.nnnMETHODSnA total of 20 patients with dementia and 40 patients with mild cognitive impairment (MCI) as well as 40 healthy control subjects were investigated for their subjective (category scale), facial (FACS) and motor (R-III reflex) pain responses to mechanical and electrical stimuli.nnnRESULTSnPatients with dementia did not rate the intensity of the stimuli differently; however, they were less frequently capable of providing ratings. At equal levels of stimulus intensity, demented patients showed stronger facial responses. The R-III reflex thresholds were lowered in demented patients. MCI patients appeared only slightly changed.nnnCONCLUSIONSnOur findings suggest that the processing of acute noxious stimuli is intensified in patients with dementia. Against the background of a reduced prescription of analgesics, an under-treatment of pain in patients with dementia might be the consequence.ZusammenfassungHintergrundEs ist bekannt, dass Demenzpatienten weniger Schmerzmittel erhalten und weniger über Schmerzen klagen als kognitiv Gesunde. Hieraus ergibt sich die Frage, ob Demenzerkrankungen die Schmerzverarbeitung verändern.MethodenAn 20xa0Patienten mit Demenz und 40 mit leichter kognitiver Beeinträchtigung (LKB) sowie 40 Kontrollpersonen wurden die verbalen (Kategorialskala), mimischen (FACS) und motorischen Schmerzreaktionen (R-III-Reflex) auf mechanische und elektrische Reize erfasst.ErgebnisseDemenzpatienten schätzten die Stärke der Schmerzreize nicht anders ein, waren jedoch seltener hierzu in der Lage. Bei gleich starken Reizen reagierten die Demenzpatienten mimisch stärker; die Schwelle ihres R-III-Reflexes war vermindert. LKB-Patienten erwiesen sich in allen Schmerzparametern nur tendenziell verändert.SchlussfolgerungUnsere Daten weisen daraufhin, dass die Verarbeitung akuter nozizeptiver Reize bei Demenzpatienten verstärkt ist. Vor dem Hintergrund der selteneren Analgetikaverordnung könnte dies auf eine schmerztherapeutische Unterversorgung von Demenzpatienten hindeuten.AbstractBackgroundIt is well known that patients with dementia complain less about pain and receive fewer analgesics than other patients. The question arises of whether disorders associated with dementia change the processing of pain.MethodsA total of 20xa0patients with dementia and 40xa0patients with mild cognitive impairment (MCI) as well as 40 healthy control subjects were investigated for their subjective (category scale), facial (FACS) and motor (R-III reflex) pain responses to mechanical and electrical stimuli.ResultsPatients with dementia did not rate the intensity of the stimuli differently; however, they were less frequently capable of providing ratings. At equal levels of stimulus intensity, demented patients showed stronger facial responses. The R-III reflex thresholds were lowered in demented patients. MCI patients appeared only slightly changed.ConclusionsOur findings suggest that the processing of acute noxious stimuli is intensified in patients with dementia. Against the background of a reduced prescription of analgesics, an under-treatment of pain in patients with dementia might be the consequence.