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194 Abstracts / Scandinavian Journal of Pain 3 (2012) 173–198 · and central post-stroke pain (CPSP). The objectives of this study. Abstracts / Scandinavian Journal of Pain 3 (2012)

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Page 1: 194 Abstracts / Scandinavian Journal of Pain 3 (2012) 173–198 · and central post-stroke pain (CPSP). The objectives of this study. Abstracts / Scandinavian Journal of Pain 3 (2012)

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94 Abstracts / Scandinavian Jo

26

echanical sensitivity in migraine patients during attack,emission, and pain-free periods: A preliminary study

. Jensen 1,∗, M.R. Sørensen 1,∗, A. Karshenas 2, F.W. Bach 2, B.E.airns 3, L. Arendt-Nielsen 1, P. Gazerani 1

Department of Health Science and Technology, Center for Sensory-otor Interaction, Aalborg University, Aalborg, DenmarkNeurological Department, Aalborg Hospital North, Aalborg, DenmarkFaculty of Pharmaceutical Sciences, University of British Columbia,ancouver, BC, Canada

Background/aims: Data on mechanical sensitivity and cuta-eous allodynia in different types and phases of migraineeadaches are limited. Existence and pattern of such symptomsay advance the understanding of neurophysiological mecha-

isms, assist clinical evaluation of the patients, and further improveanagement. Hence, in a large controlled study on migraine

atients, mechanical sensitivity and cutaneous allodynia weressessed together with clinical markers.

Methods: Sensitivity to mechanical stimuli was measured inigraine patients during attack (within 2 h of headache onset),ithin remission phase (48–72 h after headache onset), and inain-free periods (>5 days pain-free) in comparison with sex-nd age-matched healthy controls. Pin-prick stimulation was per-ormed in the temple region in the pain-referred side usingeight-calibrated pins (8, 16, 32, 64, 128, 256 mN) in a randomized

rder (3 stimuli lasting 2 s), with the patient rating the sensationn a 10-point numerical scale. Pressure Pain Threshold (PPT) wasssessed using a handheld algometer (1 cm2 rubber probe) over thenterior aspect of the temporal muscle (30 kPa/s, 3 times).

Results: Preliminary analysis revealed increased mechanicalensitivity to Pin-prick during all phases in migraine patients (n = 4)ompared to healthy controls (n = 5), and likewise increased duringttack and remission phases compared to pain-free periods withinatients. PPT, assessing mainly muscle nociception, showed a ten-ency to decline during attack and remission phases (89 ± 13% and2 ± 6%, respectively) compared to pain-free periods, with evenigher sensitivity during attack and remission phases (80 ± 12% and5 ± 11.1%, respectively) compared to healthy controls.

Conclusion: The current preliminary observed tendenciesmply the presence of mechanical hypersensitivity in migraineatients with a notable change during attack and remission phases.his study is ongoing and no firm conclusion can be stated. In addi-ion, alteration of mechanical sensitivity in different phases will be

orrelated to objective assessments of biological markers in serumpecimens of the study population.

ttp://dx.doi.org/10.1016/j.sjpain.2012.05.056

of Pain 3 (2012) 173–198

F27

Multivariate pattern analysis of evoked brain potentials by tem-poral matching pursuit and support vector machine

Carina Graversen 1,2, Christina Brock 1,∗, Jens Brøndum Frøkjær 2,Georg Dimcevski 3, Dario Farina 4, Asbjørn Mohr Drewes 1,5

1 Mech-Sense, Department of Gastroenterology, Aalborg Hospital,Aarhus University Hospital, Aalborg, Denmark2 Mech-Sense, Department of Radiology, Aalborg Hospital, Aarhus Uni-versity Hospital, Aalborg, Denmark3 Department of Endocrinology and the Hormone Laboratory, Hauke-land University Hospital, Bergen, Norway4 Department of Neurorehabilitation Engineering, Bernstein Center forComputational Neuroscience, University Medical Center Göttingen,Georg-August University, Göttingen, Germany5 Center for Sensory-Motor Interactions (SMI), Department of HealthScience and Technology, Aalborg University, Aalborg, Denmark

Background/aims: Electroencephalography (EEG) recorded asevoked brain potentials (EPs) reflects the cortical processing to anexternal event. This approach is often used to study the alteredresponse to acute pain in chronic pain patients compared to healthyvolunteers. However, discrimination of the responses from thestudy populations is a non-trivial task, which calls for improvedobjective methods.

Methods: To develop and validate a new methodology, we ana-lyzed data from 16 type-1 diabetes mellitus patients and 15 age andgender matched volunteers, by means of brain activity recordedfrom 62 EEG channels. The EEG signals were recorded as EPs elicitedby painful electrical stimulations in the oesophagus with an inten-sity corresponding to the individual pain detection threshold. TheEPs from all channels and subjects were decomposed simultane-ously by a temporal matching pursuit (TMP) algorithm with Gaboratoms.

Results: Amplitude and phase features were classified by a sup-port vector machine (SVM) to discriminate patients from healthyvolunteers. A classification performance of 93.1% (P < 0.001) wasobtained when applying a majority voting scheme to the 3 bestperforming channels (FC4, C1, and C6) and including features from2 atoms. The most discriminative features were determined by theslope coefficients from the SVM decision rule, which identified thebiomarkers as delayed latency of the first atom (N2–P2 complex)and decreased amplitude of the second atom (NI–P1 complex).

Conclusion: The combination of TMP and SVM is a novelapproach to classify two study populations, which may provide anew objective tool to identify biomarkers from various chronic painpopulations.

http://dx.doi.org/10.1016/j.sjpain.2012.05.057

F28

Pain following stroke: A prospective study

Anne P. Hansen 1,∗, Ninna S. Marcussen 1, Henriette Klit 1, HelgeKasch 2, Troels S. Jensen 1,3, Nanna B. Finnerup 1,2,3

1 The Danish Pain Research Center, Aarhus University, Aarhus,Denmark2 The Headache Clinic, Aarhus University hospital, Aarhus, Denmark3 The Department of Neurology, Aarhus University Hospital, Aarhus,Denmark

Background/aims: Pain following stroke is common and affectsthe quality of life in stroke survivors. The most common types ofpain following stroke are headache, shoulder pain, other joint painand central post-stroke pain (CPSP). The objectives of this study

Page 2: 194 Abstracts / Scandinavian Journal of Pain 3 (2012) 173–198 · and central post-stroke pain (CPSP). The objectives of this study. Abstracts / Scandinavian Journal of Pain 3 (2012)

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finally met for examination.Results: Six of the 12 women had pain in the area of surgery,

three were pain-free, but reported sensory changes and threereported no pain or sensory disturbances. We performed a detailed

Table 1Number in each group (subjects with pain vs. subjects without pain) showing pres-ence of sensory characteristics.

Pain(N = 6)

No pain(N = 6)

QuestionnaireHypoesthesia 5 3Hyperesthesia 6 3ExaminationHypoesthesia (tactile, heat, cold) 6 6

Abstracts / Scandinavian Jo

ere to determine the prevalence of pain at stroke onset and 6onths after stroke and classify the different pain types.Methods: All consecutively eligible patients admitted to the

troke Unit at Aarhus University Hospital from February 1 toctober 1, 2007 and from February 1 to August 1, 2008 were

ncluded. An interview on pain prior to and at stroke onset wasonducted at admission followed by interviews on current pain byhone 3 and 6 months after the stroke.

Results: A total of 300 patients were included in the study, and75 of them completed the 6-month follow-up. The mean age of the75 patients was 65.9 years old and 55.2% was male. Pain prior totroke was reported by 49.1% of patients at stroke onset and newlyeveloped pain defined as pain not experienced prior to stroke waseported by 37.8% at stroke onset, 41.8% at the 3-month follow-upnd 45.8% at the six month follow-up. The impact on daily life wasoderate to severe in 36.4% and 33.6% of the patients with newly

eveloped pain at the 3- and 6-month follow-up, respectively. Morehan one type of newly developed pain was experienced by 32.2%nd 36.5% at the 3- and 6-month follow-up. Headache was reportedy 33.5% at stroke onset and newly developed headache by 15.3% at-month follow-up and 13.1% at 6-month follow-up. Shoulder painas reported by 1.5%, 13.1% and 16.4% at stroke onset, and the 3-

nd 6-month follow-up, respectively. Other joint pain was reportedy 7.4% at 3-month and 11.7% at 6-month follow-up. Evoked painas experienced by 3.6% at stroke onset and by 5.5% and 9.1% at

he follow-up interviews.Other types of pain were also reported; 7.3% at stroke onset,

8.9% at 3-month follow-up and 20.0% at 6-month follow-up. Pos-ible CPSP was identified in 10.5% of patients from the different painroups.

Conclusion: Pain following stroke is common and may have aonsiderable effect on the everyday life of the patient.

ttp://dx.doi.org/10.1016/j.sjpain.2012.05.058

29

hronic thoracic pain in children after cardiac surgery

nders Due Kristensen 1,2,∗, Mette Høj Lauridsen 3, Vibeke E.jortdal 4, Troels S. Jensen 2, Lone Nikolajsen 1,2

Department of Anaesthesiology, Aarhus University Hospital, Aarhus,enmarkDanish Pain Research Center, Aarhus University Hospital, Aarhus,enmarkDepartment of pediatrics, Aarhus University Hospital, Aarhus,enmarkDepartment of Cardiothoracic and Vascular Surgery, Aarhus Univer-ity Hospital, Aarhus, Denmark

Background: Chronic pain after surgical procedures in childrenas gained limited attention. Chronic thoracic pain after cardiacurgery is common, and has a significant impact on daily life indults. The study aim was to investigate the prevalence and etiologyf chronic pain after cardiac surgery via sternotomy in children.

Methods: The study included a prospective clinical examina-ion with quantitative sensory testing 3 months after surgery, andretrospective survey of children, who underwent cardiac surgery0–60 months earlier. Children were to be at least 4 years old athe time of completing the questionnaire. They were asked to recall

he intensity of the post-operative pain. The questionnaire assessedain descriptors, situations or activities that could worsen pain, andnalgesic consumption. Faces pain scales (0–10) was used to ratehe pain intensity.

of Pain 3 (2012) 173–198 195

Results: Ten children were examined three months aftersurgery. One child reported ongoing pain. Brush allodynia and pin-prick hyperalgesia were present in 4 and 6 children respectively.Hypoesthesia to cold (20 ◦C) was present in 3 children, and coldallodynia was present in one child in the scar area. The averagepressure pain threshold was 71.1 kPa (range 34.3–121 kPa).

One hundred and seventy one questionnaires were sent out,and 121 (70.8%) were eligible for analysis. Mean age at the timeof surgery was 4.7 years and mean age at questionnaire comple-tion was 8.4. Worst pain intensity in the week after surgery was5.6 (mean). Any pain “during the recent week” was reported by26 children, 12 children reported pain intensity ≥4. Two children(1.17%) reported pain intensity ≥4 at the time of questionnairecompletion. Pain was evoked by local pressure in 23 (19.0%), andphysical activity in 15 (12.4%) children. Itch and pressing were themost frequent pain descriptors chosen by 25 (20.7%) and 20 (16.5%)children, respectively. One child used paracetamol once a week.

Conclusions: The prevalence of chronic pain following cardiacsurgery via median sternotomy in children is low. The pain mayhave a neuropathic component, but appears to be mild and doesnot significantly affect daily activities.

http://dx.doi.org/10.1016/j.sjpain.2012.05.059

F30

Chronic pain after breast augmentation is associated with bothsigns of peripheral nerve injury and central nervous mecha-nisms

T. Kaasa, L. Romundstad, A. Stubhaug ∗

Department of Pain Management and Research, Division of Emergen-cies and Critical Care, Oslo University Hospital, and Faculty of Medicine,University of Oslo, Norway

Background/aims: The mechanisms behind chronic postsur-gical pain remains unsettled. Quantitative sensory testing andquestioning sensory function may help understand mechanismsbehind the transition from acute to chronic pain. The aim of thisstudy was to assess these aspects in postsurgical patients with andwithout chronic postsurgical pain.

Methods: 116 women, who answered a questionnaire in a fouryears follow-up study of pain, sensory changes and quality of lifeafter cosmetic breast augmentation surgery [1], were invited toparticipate in a psychophysical study. Twenty women answeredthe request and filled in a questionnaire, and 12 of these women

Hypersensitivity detected 4 1Hyperpathia to heat 5 5Paradoxical heat sensation during cold stimulation 4 0Allodynia, cotton 0 0Allodynia, brush 0 1Cold allodynia 5 1Abnormal temporal summation 5 1Deep pain after algometry 4 0