Recovery cycle of the blink reflex and exteroceptive suppression of temporalis muscle activity in migraine and tension-type headache

Brain stem interneuronal excitability can be assessed by recording the reco very cycle of the blink reflex and exteroceptive suppression of temporalis muscle activity. Abnormal endogenous pain control mechanisms due to disturb ed brain stem interneuronal activity have been implicated in the pathogenes is of tension-type headaches. The blink reflex, exteroceptive suppression o f temporalis muscle activity, and the recovery curve of both the R2 compone nt of the blink reflex and the ES2 component of the exteroceptive suppressi on of the temporalis muscle activity were studied in 20 patients with migra ine without aura, 32 patients with tension-type headache, and 20 normal con trols. In our study, the blink reflex was elicited by stimulation of the su praorbital nerve; the exteroceptive suppression of the temporalis muscle ac tivity was elicited by applying electrical shocks to the labial commis sure , both on the lower and upper sides. The recovery cycle was established by delivering paired shocks at different interstimulus intervals. Comparisons were made between normal control subjects, patients with migraine without a ura, and patients with tension-type headache. The latency of R1, R2, and R2 ', the amplitude and size of the R2 and R2' components of the blink reflex, the latency and duration of the ES1 and ES2 components, and the recovery c urve of the ES2 component of the temporalis muscle activity did not differ between groups. However, the recovery curve of the R2 component of the blin k reflex diminished in patients with tension-type headache compared with th e other groups. Our findings indicate reduced excitability of the brain ste m interneurons in patients with tension-type headache.