TRIGEMINO-CERVICAL REFLEXES IN NORMAL SUBJECTS

Trigemino-cervical reflexes, recorded from the semispinalis capitis mu scle (SCM) in the posterior neck, were studied in 35 healthy volunteer s, in response to electrical stimulation of the supraorbital trigemina l nerve and glabellar tapping. Simultaneous responses evoked from the ipsilateral orbicularis oculi muscle (OOM) were also recorded i.e. bli nk reflexes. Electrical stimulation of the supraorbital nerve elicited a reflex response with a latency of about 50 ms from the ipsilateral SCM which was called C3. An early reflex response, which sometimes had two components with latencies of 18 ms and 35 ms, was elicited with g labellar taps. They were called C1 and C2 respectively. When CI and C2 were elicited with usual glabellar taps, C3 was suppressed. With elec trical stimulation, suppression of C1 and C2 was noted, though C3 coul d easily be obtained. Electrophysiological characteristics of Cc (and C2) were compatible with an oligosynaptic, innocuous reflex, whereas C 3 seemed to be multisynaptic and nociceptive in nature. A negative int eraction between these two reflexes was observed.