OBJECTIVE: To determine if the activity of jaw and neck muscles in a rat model is influenced by the application of small-fiber irritant mustard oil to meningeal/dural vascular tissues.

DESIGN: Controlled animal experiment.

SETTING: University neurophysiology laboratory.

INTERVENTIONS: Applications of mineral oil (vehicle control) and mustard oil to exposed meningeal/dural vascular tissues.

MAIN OUTCOME MEASURE: Electromygraphic (EMG) recordings from deep suboccipital muscles, bilaterally, and the left trapezius and left masseter muscles.

RESULTS: Mineral oil evoked no EMG responses in any muscles. The incidences of mustard oil-evoked EMG increases were 100%, 100%, 89% and 78% for left deep neck, right deep neck, left trapezium and left masseter muscles, respectively. The durations of EMG responses were (mean +/- SD) 19.2 +/- 6.6 min, 17.3 +/- 7.5 min, 14.5 +/- 6.8 min and 12.7 +/- 8.5 min, respectively.

CONCLUSIONS: These results document that meningeal/dural vascular irritation leads to sustained and reversible activation of neck and jaw muscles that may be related to the clinical occurrence of muscular tension and pain associated with certain types of headaches, particularly migraine.

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