Nociceptive trigeminocervical reflexes in healthy subjects.
OBJECTIVE
Electrical stimulation of the supraorbital trigeminal nerve branch induces trigeminocervical reflex responses (TCRs) in the neck muscles. The purpose of this study was to elicit more nociceptive TCR responses through preferential activation of the nociceptive afferents with a concentric surface electrode.


METHODS
We recorded TCRs in 10 healthy subjects using both a standard (sTCR) and a nociceptive (nTCR) concentric surface electrode. We compared the baseline parameters, stimulus intensity/response, recovery, and habituation curves recorded for the two types of electrode, and assessed the effects of local anaesthesia.


RESULTS
Compared with the sTCRs, nTCRs showed a significantly longer latency of the late reflex component, as well as lower pain and higher reflex thresholds. They also showed a different recovery cycle and stimulus intensity/response curve, but similar habituation rate. Local anaesthesia attenuated by 85% the late reflex response to stimulation by the concentric electrode, and by only 15% the response to standard electrode stimulation.


CONCLUSIONS
The differences observed stimulating with these two electrode types may be due to their different activation of the afferent fibres.


CONCLUSIONS
If this study were extended to patients affected by primary headaches, TCR monitoring could emerge as a sensitive tool for detecting changes in nociceptive transmission at the level of trigeminocervical complex.
Serrao
Mariano
M
"Sapienza" University of Rome, Polo Pontino, Rome, Italy; IRCCS-Neuromed, Pozzilli, IS, Italy. Electronic address: mariano.serrao@uniroma1.it.
Coppola
Gianluca
G
G.B. Bietti Eye Foundation-IRCCS, Dept. of Neurophysiology of Vision and Neurophthalmology, Rome, Italy.
Di Lorenzo
Cherubino
C
University Centre for Adaptive Disorders and Headache (UCADH), "Sapienza" University of Rome, Polo Pontino, I.C.O.T., Latina, Italy.
Di Fabio
Roberto
R
"Sapienza" University of Rome, Polo Pontino, Rome, Italy.
Padua
Luca
L
Don Carlo Gnocchi Onlus Foundation, Italy.
Sandrini
Giorgio
G
University Centre for Adaptive Disorders and Headache (UCADH), IRCCS C. Mondino Foundation, Pavia, Italy.
Pierelli
Francesco
F
University Centre for Adaptive Disorders and Headache (UCADH), "Sapienza" University of Rome, Polo Pontino, I.C.O.T., Latina, Italy.
D000328:Adult; D000704:Analysis of Variance; D001703:Biophysics / Q000379:methods; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D006185:Habituation, Psychophysiologic; D006801:Humans; D008297:Male; D009334:Neck Muscles / Q000294:innervation; D009619:Nociceptors / Q000502:physiology*; D010147:Pain Measurement; D011930:Reaction Time / Q000502:physiology; D012018:Reflex / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology; D014276:Trigeminal Nerve / Q000502:physiology*; D055815:Young Adult