Headache
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Exteroceptive suppression of temporalis muscle activity was studied in patients with chronic headache and in healthy controls. Among different methods of recording, averaging 10 full-wave rectified EMG responses produces results with acceptable variability and discomfort. The late temporalis exteroceptive suppression period (ES2) is reduced on average in patients with chronic tension-type headache; this finding has been reproduced by several independent laboratories. ⋯ In chronic tension-type headache, excitability of these interneurons is decreased because of inadequate control by the serotonergic raphe magnus nucleus and the periaqueductal gray matter. Dysfunctioning of the latter structures might be caused by abnormal limbic inputs to the brain stem. Some steps of this pathophysiological hypothesis can be verified by modern neurophysiological techniques.