Objective: To investigate the masseter inhibitory reflex (MIR) and its eventual changes in patients with episodic tension-type headache (TTH).
Methods: MIR was studied in 21 patients with episodic TTH and 30 healthy subjects, with age and sex matched to the study cohort. Median age of patients was 17.0 years (ranged 16~49 years), median duration of disease 12 months (1~5 years), and median frequency of headache 7.5 d per month.
Results: The second period of suppression (S2) of MIR was reduced in intensity and duration in 10% of controls and 66.7% (confidence interval (CI)=45.3%~85%; P<0.05) of patients with episodic TTH (chi(2)=74.9; P<0.001). In 3 (14.3%) of patients with episodic TTH, S2 was completely absent. No significant correlation between the duration of disease and headache frequency was found.
Conclusion: Our results confirm the link between episodic TTH and reduction or absence of S2. Teenage patients with episodic TTH may exhibit marked pathological changes in S2 in contrast to older individuals.