Cervicogenic headache: the influence of mental load on pain level and EMG of shoulder-neck and facial muscles.

The relationship between pain and EMG levels was studied in 17 cervicogenic headache patients and 17 group-matched healthy controls. All subjects performed a 1-hour, complex, two-choice, reaction time test. Every 10 minutes before, during, and also for 20 minutes after the test, they reported pain levels (using visual analogue scales) in the forehead, both temples, neck, and shoulders. Electromyographic activity, using superficial electrodes, was also recorded from the frontal, temporal, neck (splenius), and trapezius muscles. Maximal voluntary contractions were performed in all the muscles. Increased pain levels before, during, and after the test were found on the symptomatic side in the temple, shoulder area, and neck in the patient group compared with nonsymptomatic side and controls (neck only compared with controls). Electromyographic amplitudes from the trapezius muscle on the symptomatic side were significantly higher before and during the test, compared with the nonsymptomatic side, but most markedly during the test. Pretest EMG amplitudes from the frontal muscle on the symptomatic side in patients were also significantly higher than those in controls, but the difference vanished during the test. There are indications that the temporal pain, ie, the headache, is a referred pain. These observations may point to a "muscular" involvement in the pathogenesis of cervicogenic headache, either primarily or, which seems more plausible, secondarily.