Modulation of neck muscle activity induced by intra-oral stimulation in humans.
OBJECTIVE
To investigate the effect of painful electrical stimuli applied to intra-oral tissues around the teeth on the neck muscle activity in healthy humans.


METHODS
Electromyographic (EMG) responses of the dorsal neck muscles evoked by intra-oral electrical stimulation were recorded before and after local anesthesia to the stimulus site in 17 healthy volunteers.


RESULTS
Inhibition of dorsal neck muscle EMG activities on average 80% compared to baseline level was observed with a latency around 50 ms after the electrical stimulation before anesthesia, and the EMG activity inhibition decreased after anesthesia of the intra-oral stimulus site. The perceived intensity of the electrical stimuli as scored on a visual analogue scale (VAS) was 6.1 ± 0.4 cm before anesthesia and 1.5 ± 0.2 cm after anesthesia.


CONCLUSIONS
Intra-oral stimulation can inhibit neck muscle activity. This modulation might be attributed mainly to nociceptive afferent nerves however, non-nociceptive fibers could also be responsible.


CONCLUSIONS
Intra-oral information including nociceptive activity can inhibit neck muscle activity. From a clinical viewpoint, the present findings demonstrate the neural connectivity between the trigeminal region and the cervical region raising the possibility that orofacial pain conditions could influence head, neck and shoulder activity.
Department of Prosthetic Dentistry, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan; Center for Sensory-Motor Interaction (SMI), Laboratory for Human Experimental Pain Research, Aalborg University, Fredrik Bajers Vej 7 D-3, DK-9220 Aalborg, Denmark. Electronic address: torisu@nagasaki-u.ac.jp.
Tetsurou
T
Torisu
Department of Prosthetic Dentistry, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
Mihoko
M
Tanaka
Department of Prosthetic Dentistry, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
Hiroshi
H
Murata
Center for Sensory-Motor Interaction (SMI), Laboratory for Human Experimental Pain Research, Aalborg University, Fredrik Bajers Vej 7 D-3, DK-9220 Aalborg, Denmark.
Kelun
K
Wang
Center for Sensory-Motor Interaction (SMI), Laboratory for Human Experimental Pain Research, Aalborg University, Fredrik Bajers Vej 7 D-3, DK-9220 Aalborg, Denmark.
Lars
L
Arendt-Nielsen
Cluster of Oral Physiology, Department of Oral Health Sciences, KU Leuven and Dentistry, University Hospitals Leuven, Belgium.
Antoon
A
De Laat
Section of Clinical Oral Physiology, School of Dentistry, Aarhus University, Aarhus, Denmark.
Peter
P
Svensson
D000328:Adult; D004558:Electric Stimulation; D004576:Electromyography; D005157:Facial Pain / Q000150:complications / Q000503:physiopathology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008406:Masseter Muscle / Q000294:innervation / Q000502:physiology; D009334:Neck Muscles / Q000294:innervation / Q000502:physiology*; D019547:Neck Pain / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D059225:Nociception / Q000502:physiology; D010147:Pain Measurement; D012016:Reference Values; D012018:Reflex / Q000502:physiology*; D013705:Temporomandibular Joint Disorders / Q000150:complications / Q000503:physiopathology
Electromyography (EMG); Intra-oral stimulation; Pain; Temporomandibular disorders; Trigemino-cervical reflex