Assessment of nociceptive trigeminal pathways by laser-evoked potentials and laser silent periods in patients with painful temporomandibular disorders.
We assessed the trigeminal nociceptive pathways in patients with painful temporomandibular disorders (TMD) and control subjects using a CO(2)-laser stimulator which provides a predominant activation of the nociceptive system. Fifteen patients with unilateral pain were examined in accordance with the Research Diagnostic Criteria for TMD and 30 gender- and age-matched individuals were included as a control group. Laser-evoked potentials (LEPs) and laser silent periods (LSPs) after stimulation of the perioral region (V2/V3) on the painful and non-painful sides were recorded in all subjects. LEPs were evoked by low-intensity pulses (1.5 x perception threshold (PTh)) and recorded from scalp electrodes at the vertex. LSPs were evoked by high-intensity pulses (4 x PTh) and recorded bilaterally from masseter muscles with surface electromyogram (EMG) electrodes. Subjects also assessed the stimulus intensity on a 0-10 rating scale. LEPs had normal latency but smaller amplitude in TMD patients compared to the control group (P<0.001). Side-to-side comparison within patients showed that LEP amplitude was even more reduced after stimulation on the painful than the non-painful side (P<0.001). TMD patients showed a significant side-asymmetry of the pre-stimulus EMG activity, with a smaller value in the muscle on the painful side (P<0.001). LSPs were completely absent bilaterally in 12 TMD patients and unilaterally in two patients; only one patient had normal and bilateral LSPs. TMD patients perceived the laser stimulus less intense on the painful than the non-painful side (P<0.05). We found suppression of cortical responses and brainstem reflexes elicited by a predominantly nociceptive input in TMD patients. These findings are consistent with recent experimental pain studies and suggest that chronic craniofacial pain in TMD patients may be associated with a dysfunction of the trigeminal nociceptive system.
Center for Sensory-Motor Interaction, Orofacial Pain Laboratory, Aalborg University, Aalborg, Denmark.
A
A
Romaniello
G
G
Cruccu
G
G
Frisardi
L
L
Arendt-Nielsen
P
P
Svensson
D000328:Adult; D001921:Brain / Q000528:radiation effects; D002245:Carbon Dioxide; D016022:Case-Control Studies; D002908:Chronic Disease; D004307:Dose-Response Relationship, Radiation; D004576:Electromyography / Q000295:instrumentation; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D007834:Lasers; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways / Q000503:physiopathology; D010146:Pain / Q000209:etiology / Q000503:physiopathology*; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold; D013705:Temporomandibular Joint Disorders / Q000150:complications / Q000503:physiopathology* / Q000523:psychology; D020433:Trigeminal Nerve Diseases / Q000503:physiopathology*
D002245:Carbon Dioxide