title: Normal laser-evoked cortical responses in patients with chronic hemibody pain.
abstract: BACKGROUND
  Patients with widespread unilateral chronic pain associated with recurrent herpes simplex virus (HSV) infections show functional and/or structural changes in the insula, anterior cingulate cortex, frontal and prefrontal cortices, as well as the thalamus, suggesting central dysfunction of the pain system in these patients. Central pain has been associated with attenuated laser-evoked cortical responses. We aimed to clarify whether the observed deficient activation of these areas to acute nociceptive stimuli is due to a lesion at a lower level of pain processing pathways.
  
  
  METHODS
  We explored the functional integrity of the ascending nociceptive pathways by recording the cortical-evoked responses to noxious laser stimulation using magnetoencephalography and electroencephalography in eight patients (age 41-51 years, mean 46) with recurrent HSV infections and a history of chronic, spontaneous, widespread unilateral pain, and in nine age-matched healthy control subjects.
  
  
  RESULTS
  The cortical-evoked fields of the HSV patients originating from the secondary somatosensory and posterior parietal cortices, as well as the evoked potentials recorded from the midline, did not differ from those of the control subjects, indicating functionally intact ascending nociceptive pathways.
  
  
  CONCLUSIONS
  The present results show that our patients with chronic hemibody pain do not show signs of spinothalamic tract lesion. This indicates normal processing of sensory aspects of painful stimuli, while higher pain processing areas show altered activation. We conclude that normal laser-evoked magnetic fields (LEF) or laser-evoked potentials (LEP) may not exclude central pain condition.
authors.affiliation: Brain Research Unit and MEG Core, O.V. Lounasmaa Laboratory, Aalto Neuroimaging, School of Science, Aalto University, Espoo, Finland.|Department of Clinical Neurophysiology, HUS Medical Imaging Center, Helsinki University Central Hospital, Finland.|Department of Neurological Sciences, University of Helsinki, Finland.
authors.forename: E
authors.initials: E
authors.lastname: Kirveskari
authors.affiliation: Brain Research Unit and MEG Core, O.V. Lounasmaa Laboratory, Aalto Neuroimaging, School of Science, Aalto University, Espoo, Finland.
authors.forename: N V
authors.initials: NV
authors.lastname: Vartiainen
authors.affiliation: Department of Anaesthesia and Intensive Care Medicine, Pain Clinic, Helsinki University Central Hospital, Finland.
authors.forename: K
authors.initials: K
authors.lastname: Kallio-Laine
authors.affiliation: Department of Anaesthesia and Intensive Care Medicine, Pain Clinic, Helsinki University Central Hospital, Finland.|Institute of Clinical Medicine, Faculty of Medicine, University of Helsinki, Finland.
authors.forename: E
authors.initials: E
authors.lastname: Kalso
authors.affiliation: Brain Research Unit and MEG Core, O.V. Lounasmaa Laboratory, Aalto Neuroimaging, School of Science, Aalto University, Espoo, Finland.|Department of Neurological Sciences, University of Helsinki, Finland.|Department of Neurology, Helsinki University Central Hospital, Finland.
authors.forename: N
authors.initials: N
authors.lastname: Forss
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000503:physiopathology*; D059350:Chronic Pain / Q000503:physiopathology*; D004574:Electromagnetic Fields; D005071:Evoked Potentials; D005260:Female; D007839:Functional Laterality; D006561:Herpes Simplex / Q000150:complications / Q000473:pathology; D006801:Humans; D066331:Laser-Evoked Potentials; D007834:Lasers; D015225:Magnetoencephalography; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways / Q000503:physiopathology; D009619:Nociceptors / Q000473:pathology; D010147:Pain Measurement; D017288:Pain Threshold; D013003:Somatosensory Cortex / Q000503:physiopathology