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© 2007 American Academy of Neurology Neurophysiologic study of central pain in patients with Parkinson diseaseFrom Medical Sciences Post-Graduation Course (P.S., M.L.C.), UFRGS School of Medicine, Porto Alegre, Brazil; Institut Guttmann (H.K.), Barcelona, Spain; Department of Neurology (J.V.-S., F.V., M.J.M., E.T.), Hospital Clínic, Universidad de Barcelona, IDIBAPS (Institut d’Investigacio Biomédica August Pi i Sunyer), CIBERNED (Centro de Investigación Biomédica en Red sobíre Enfermedades Neurodegenerativas), Barcelona, Spain; and Neurology Service (M.L.C.), Hospital de Clínicas de Porto Alegre, Brazil. Address correspondence and reprint requests to Dr. Josep Valls-Solé, EMG Unit, Neurology Department, Hospital Clínic, Villarroel, 170 Barcelona, 08036 Spain Background: Patients with Parkinson disease (PD) may present with various types of pain. In some instances, no cause can be identified and pain is considered a primary disorder (primary central pain [PCP]). We hypothesized that PCP in patients with PD (PD-PCP) may be due to a dysfunction of pain pathways or the processing of pain inputs in the CNS. Methods: We carried out a psychophysical and neurophysiologic study in 9 patients with PD-PCP, 9 patients with PD without pain (PD-NoP), and 9 healthy control subjects. We assessed the clinical characteristics of pain, performed quantitative sensory testing with thermal probes, and recorded laser-evoked potentials (LEPs) and laser-induced sudomotor skin responses (l-SSRs) in "off" and "on" conditions. Results: In "off" condition, patients with PD-PCP had lower heat pain and laser pinprick thresholds, higher LEP amplitudes, and less habituation of the l-SSR in comparison with PD-NoP patients and control subjects. Abnormalities were more marked in the most affected side. In "on" condition, psychophysical and neurophysiologic differences disappeared or were significantly attenuated. Conclusion: Conduction along peripheral and central pain pathways is normal in patients with Parkinson disease with or without primary central pain. However, apart from signs of hyperalgesia, our patients exhibited lack of habituation of sympathetic sudomotor responses to repetitive pain stimuli, suggesting an abnormal control of the effects of pain inputs on autonomic centers. Abnormalities were attenuated by l-dopa, suggesting that the dysfunction may occur in dopamine-dependent centers regulating both autonomic function and inhibitory modulation of pain inputs.
Abbreviations: ADL = activities of daily living; ANS = autonomic nervous system; HI = habituation index; l-SSRs = laser-induced sudomotor skin responses; LAS = less affected side; LEPs = laser-evoked potentials; MAS = more affected side; PAG = periaqueductal gray matter; PCP = primary central pain; PD = Parkinson disease; PD-NoP = PD without pain; UPDRS = Unified Parkinson’s Disease Rating Scale; VAS = visual analogue scale.
Supported by a grant from CAPES, Brazil, to P.S. Disclosure: The authors report no conflicts of interest. Received January 29, 2007. Accepted in final form May 31, 2007. This article has been cited by other articles:
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