Late component of trigemino-cervical reflex: changes according to age and gender.

BACKGROUND: Trigemino-cervical reflex (TCR) is a protective reflex which is elicited by the stimulation of any branch of the trigeminal nerve. After infraorbital stimulation, an early and late components have been described. The aim of this study was to find out whether there are age- or gender-related changes in the long-latency (RII) component of TCR. METHOD: We included consecutive 53 healthy subjects (20 men, 37.7%) who had normal neurological examination. The mean age was 45.1 ± 14.3 years (age range 18-75 years). TCR was recorded simultaneously from bilateral sternocleidomastoid (SCM) and splenius capitis (SC) muscles with surface electrodes after stimulating right or left infraorbital branch of the trigeminal nerve, separately. We compared latency, amplitude, and duration according to gender and age. RESULTS: The amplitudes of SC responses were significantly higher in women compared to men. The duration of SCM response was significantly longer in subjects above the age of 50 years compared to younger patients. The latency of the SC response was significantly delayed above the age of 40 years. CONCLUSION: There are age- and gender-related changes in TCRs probably due to changes in the motoneurons of the SC and SCM muscles.