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Normal laser‐evoked cortical responses in patients with chronic hemibody pain
Author(s) -
Kirveskari E.,
Vartiainen N.V.,
KallioLaine K.,
Kalso E.,
Forss N.
Publication year - 2015
Publication title -
european journal of pain
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.305
H-Index - 109
eISSN - 1532-2149
pISSN - 1090-3801
DOI - 10.1002/ejp.642
Subject(s) - spinothalamic tract , nociception , neuroscience , somatosensory system , thalamus , lesion , magnetoencephalography , medicine , chronic pain , sensory system , anterior cingulate cortex , somatosensory evoked potential , psychology , stimulation , insula , cingulate cortex , central nervous system , electroencephalography , pathology , receptor , cognition
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.