Background and aims : In migraine pathophysiology, the link between the visual cortex and the trigeminovascular system might play a pivotal role. In a previous study we showed the top-down relation between the visual cortex and the trigeminal nociceptive system.
To search for the existence of a bottom-up relationship we studied the effect of electrical stimulation or application of capsaicin in
... [Show full abstract] the territory of the 1st division of the trigeminal nerve on pattern-reversal visual evoked potentials (PR-VEP).
Methods: We recorded 600 responses of PR-VEP at 3.1 Hz before and after the trigeminal stimulation. The electrical stimuli were delivered over the supraorbital nerve for 20 min at 16 mA and 100 Hz in 7 healthy volunteers (HV). Capsaicin (cream 3%) was applied over the right frontal area for 1h in 8 HV. We measured PR-VEP N1, P1 and N2 latencies, N1-P1 and P1-N2 amplitudes in six sequential blocks of 100 sweeps and habituation as the change in amplitude over the six blocks.
Results: The electrical stimulation increased the latency of P1 (p=0.027) and N2 (p=0.042) but left habituation unchanged. The capsaicin application increased habituation between the 1st and 2nd block of 100 responses (p=0.049) but had no significant effect on latencies.
Conclusions: These results suggests that a bottom-up relation exists between the trigeminal (V1) afferent nociceptive pathway and the visual cortex. Interestingly, an increase in PR-VEP habituation, such as found after capsaicin, also occurs during the migraine attack, where it replaces the interictal deficit of habituation. Sava SL, Schoenen J (2011) Repetitive transcranial magnetic stimulation modulates the nociceptive-specific blink reflex in healthy subjects but not in migraineurs. Cephalalgia, IHS-Berlin
Sava SL, Schoenen J (2010) Repetitive transcranial magnetic stimulation over the visual cortex modulates trigeminal nociceptive pathways. EHMTIC-Nice
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