title: Abnormal processing of the nociceptive input in Parkinson's disease: a study with CO2 laser evoked potentials.
abstract: Since a number of patients with Parkinson's Disease (PD) complain of painful sensations, we studied whether the central processing of nociceptive inputs is abnormal in PD. To test this hypothesis, we recorded scalp CO(2) laser evoked potentials (LEPs) to hand skin stimulation in 18 pain-free PD patients with unilateral bradykinetic-rigid syndrome (hemiparkinson) during the off state and in 18 healthy subjects. This technique allows us to explore non-invasively the functional status of some cerebral structures involved in nociceptive input processing. In both PD patients and control subjects, CO(2) laser stimulation gave rise to a main negative N2 potential followed by a positive P2 response at vertex peaking at a latency of about 200 and 300ms, respectively. These potentials are thought to originate from several brain structures devoted to nociceptive input processing, including the cingulate gyrus and insula. PD patients and normal subjects showed comparable N2 and P2 latencies, whereas the N2/P2 peak-to-peak amplitude was significantly lower in PD patients (regardless of the clinically affected body side) than in controls. LEPs were even recorded after acute L-dopa administration in 7 additional PD patients. L-dopa administration yielded no significant change in N2/P2 amplitude as compared to the off state. These results suggest an abnormal nociceptive input processing in pain-free PD patients which appears to be independent of clinical expression of parkinsonian motor signs and is not affected by dopaminergic stimulation.
authors.affiliation: Dipartimento di Scienze Neurologiche e della Visione, Sezione di Neurologia Riabilitativa, Università di Verona, Italy. michele.tinazzi@mail.azosp.vr.it
authors.forename: Michele
authors.initials: M
authors.lastname: Tinazzi
authors.forename: Claudia
authors.initials: C
authors.lastname: Del Vesco
authors.forename: Giovanni
authors.initials: G
authors.lastname: Defazio
authors.forename: Emiliana
authors.initials: E
authors.lastname: Fincati
authors.forename: Nicola
authors.initials: N
authors.lastname: Smania
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Moretto
authors.forename: Antonio
authors.initials: A
authors.lastname: Fiaschi
authors.forename: Domenica
authors.initials: D
authors.lastname: Le Pera
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Valeriani
mesh_terms: D000368:Aged; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D054020:Lasers, Gas / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000503:physiopathology* / Q000523:psychology; D010147:Pain Measurement / Q000379:methods*; D010300:Parkinson Disease / Q000503:physiopathology* / Q000523:psychology; D011930:Reaction Time / Q000502:physiology