Action of some pericranial muscles during provoked attacks of common migraine

In this electromyographic study the activity in the temporal, masseter, sternocleidomastoid and nuchal muscles was recorded bilaterally in 2 males and 2 females during attacks of common migraine precipitated with specific beverages. Muscle activity continuously picked up with bipolar surface electrodes was supplemented by pain ratings at regular intervals, and registrations of similar duration were obtained with the patients free of headache. Recordings were divided into sections of 10 min, and during the last 2 min of each section the average level and the peak of the mean voltage were assessed with intervals of 5 sec. The average of these measurements in per cent of maximal activity was used to characterize the activity in a section. The time course of muscle activity varied between patients and muscles. In general, the migraine attack was characterized by a rise of activity from control level shortly before the patients experienced maximal pain, and location of the hyperactivity corresponded reasonably well with the spatial distribution of pain and tenderness. In two patients activity was sufficiently strong to account for a substantial part of their pain.