Mariano Serrao1, Francesca Cortese2, Ole Kæseler Andersen3, Carmela Conte4, Erika G Spaich5, Gaia Fragiotta6, Alberto Ranavolo7, Gianluca Coppola8, Armando Perrotta9, Francesco Pierelli10. 1. Department of Medical-Surgical Sciences and Biotechnologies, Sapienza University of Rome, Corso della Repubblica 79, 04100 Latina, Italy; Laboratory of Movement Analysis, Policlinico Italia, Piazza del Campidano 6, 00162 Rome, Italy. Electronic address: mariano.serrao@uniroma1.it. 2. Department of Medical-Surgical Sciences and Biotechnologies, Sapienza University of Rome, Corso della Repubblica 79, 04100 Latina, Italy. Electronic address: francesca.cortese05@libero.it. 3. Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7-D3, DK-9220 Aalborg, Denmark. Electronic address: oka@hst.aau.dk. 4. Laboratory of Movement Analysis, Policlinico Italia, Piazza del Campidano 6, 00162 Rome, Italy. Electronic address: conte_carmela@libero.it. 5. Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7-D3, DK-9220 Aalborg, Denmark. Electronic address: espaich@hst.aau.dk. 6. Department of Medical-Surgical Sciences and Biotechnologies, Sapienza University of Rome, Corso della Repubblica 79, 04100 Latina, Italy. Electronic address: gaia.fragiotta@hotmail.it. 7. INAIL, Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, Via Fontana Candida 1, 00040 Monteporzio Catone, Rome, Italy. Electronic address: a.ranavolo@inail.it. 8. G.B. Bietti Foundation IRCCS, Department of Neurophysiology of Vision and Neurophthalmology, Via Livenza 3, 00198 Rome, Italy. Electronic address: gianluca.coppola@gmail.com. 9. IRCCS Neuromed, Via Atinense 18, 86077 Pozzilli, Isernia, Italy. Electronic address: armando.perrotta@neuromed.it. 10. Department of Medical-Surgical Sciences and Biotechnologies, Sapienza University of Rome, Corso della Repubblica 79, 04100 Latina, Italy. Electronic address: fpierelli@gmail.com.
Abstract
OBJECTIVE: To explore whether the trigeminocervical reflexes (TCRs) show a reflex receptive field organization in the brainstem. METHODS: The facial skin of 16 healthy subjects was electrically stimulated at nine sites reflecting the distribution of the three branches of the trigeminal nerve. The reflex-evoked EMG responses were measured bilaterally from the neck muscles and the head and neck kinematic reactions were detected. RESULTS: TCRs are site dependent. There was a vertical gradient in the magnitude of the reflex responses. EMG and kinematic reflexes were larger when evoked from ophthalmic and maxillary sites than from mandibular ones. The reflex responses exhibited a crossed right-left behavior. Stimulation of the lateral sites evoked larger reflex responses in the contralateral trapezium muscle as well as head rotation and neck bending away from the stimulated side. CONCLUSION: This modular arrangement of the TCRs seems to be related to withdrawal strategies aimed at protecting the face from injuries, in accordance with the functional role that each group of muscles plays in head and neck motion. SIGNIFICANCE: It is likely that the CNS may exploit the neck muscle synergies revealed by the painful stimulation of the skin face in order to control the head and neck movements.
OBJECTIVE: To explore whether the trigeminocervical reflexes (TCRs) show a reflex receptive field organization in the brainstem. METHODS: The facial skin of 16 healthy subjects was electrically stimulated at nine sites reflecting the distribution of the three branches of the trigeminal nerve. The reflex-evoked EMG responses were measured bilaterally from the neck muscles and the head and neck kinematic reactions were detected. RESULTS: TCRs are site dependent. There was a vertical gradient in the magnitude of the reflex responses. EMG and kinematic reflexes were larger when evoked from ophthalmic and maxillary sites than from mandibular ones. The reflex responses exhibited a crossed right-left behavior. Stimulation of the lateral sites evoked larger reflex responses in the contralateral trapezium muscle as well as head rotation and neck bending away from the stimulated side. CONCLUSION: This modular arrangement of the TCRs seems to be related to withdrawal strategies aimed at protecting the face from injuries, in accordance with the functional role that each group of muscles plays in head and neck motion. SIGNIFICANCE: It is likely that the CNS may exploit the neck muscle synergies revealed by the painful stimulation of the skin face in order to control the head and neck movements.