The blink reflex and the corneal reflex are followed by cortical activity resembling the nociceptive potentials induced by trigeminal laser stimulation in man

Heat pain thresholds and cerebral event-related potentials following painful CO2 laser stimulation in chronic tension-type headache

Current opinion concerning the pathophysiology of tension-type headache (TTH) and its related pericranial muscle tenderness proposes a primary role of central sensitization at the level of dorsalhorn/trigeminal nucleus as well as the supraspinal level. Investigation of these phenomena can be conducted using laser-evoked potentials (LEPs), which are objective and quantitative neurophysiological tools for the assessment of pain perception. In the present study we examined features of LEPs, as well as cutaneous heat-pain thresholds to laser stimulation, in relation to the tenderness of pericranial muscles in chronic TTH resulting from pericranial muscle disorder, during a pain-free phase. Twelve patients with TTH and 11 healthy controls were examined using the Total Tenderness Scoring (TTS) system. The stimulus was a laser pulse generated by a CO(2) laser. The dorsum of the hand and the cutaneous zones corresponding to pericranial muscles were stimulated. Subjective perception of stimulus intensity was assessed by a visual analogue scale. Two responses, the earlier named N2a and the last named P2, were considered; the absolute latency was measured at the highest peak of each response. The N2a-P2 components' peak-to-peak amplitude was detected. The heat pain threshold was similar in TTH patients and controls at the level of both the hand and pericranial skin. The TTS scores at almost all pericranial sites were higher in TTH patients than in normal controls. The amplitude of the N2a-P2 complex elicited by stimulation of the pericranial zone was greater in TTH patients than in controls; the amplitude increase was significantly associated with the TTS score. Our findings suggest that pericranial tenderness may be a primary phenomenon that precedes headache, and is mediated by a greater pain-specific hypervigilance at the cortical level.

Kognitive Prozesse und dynamische Zeitstrukturen. Vorstellung eines Meßgerätes zur Untersuchung der Mikro-Vigilanz-Shift-(MVS-)Hypothese. Cognitive Processes and Dynamical Time Structures. Introduction of a Method for Testing the Microvigilance Shift (MVS) Hypothesis

The psychophysiological measuring method for the determination of the auditory order threshold (OT) is steadily gaining in importance, both for the diagnosis and treatment of speech disorders. Observed intraindividual variability of (macro-) vigilance led to the hypothesis of discontinuous cognitive processing in the central nervous system. The base for the variability of microvigilance is hypothesized to be in the phase difference of the alpha rhythm. To test for this hypothesis, we developed an EEG-comparator, which allows for a phase-dependent triggering of external stimuli. In direct comparison with stochastic (i.e. non-phase-dependent) stimulus presentation, the threshold in phase-dependent OT-testing is distinctly lower. Optimal results occurred at phase angels of phi = 90 degrees and phi = 270 degrees. Our findings support the hypothesis of a correlation between alpha rhythm and vigilance processes. Furthermore, there seems to be evidence that memory processes go with changes in vigilance, and in this context the alpha phase correlation seems to be important.

Abnormal brain processing of cutaneous pain in patients with chronic migraine

Syndromes with chronic daily headache include chronic migraine (CM). The reason for the transformation of migraine into chronic daily headache is still unknown. In this study, we aimed to evaluate heat pain thresholds and event-related potentials following CO(2)-laser thermal stimulation (LEPS) in hand and facial regions in patients with CM, to show changes in nociceptive brain responses related to dysfunction of pain elaboration at the cortical level. The results were compared with findings from normal control subjects and from subjects who suffer from migraine without aura. The effects of stimulus intensity, subjective pain perception and attention were monitored and compared with features of the LEPS. Twenty-five CM patients, 15 subjects suffering from migraine without aura and 15 normal control subjects were enrolled in the study. LEPS amplitude variation was reduced in CM patients with respect to the perceived stimulus intensity, in comparison with migraine without aura patients and control subjects. In both headache groups, the distraction from the painful laser stimulus induced by an arithmetic task failed to suppress the LEPS amplitude, in comparison with control subjects. These results suggest an abnormal cortical processing of nociceptive input in CM patients, which could lead to the chronic state of pain. In both headache groups, an inability to reduce pain elaboration during an alternative cognitive task emerged as an abnormal behaviour probably predisposing to migraine.