Changes in the electro-encephalogram related to the menstrual cycle.

A comparison has been made between the electro-encephalograms (EEG) recorded in the premenstrual phase and those recorded at mid-cycle in 25 healthy young women. In only 5 could no difference be discerned visually between the two records obtained from each subject. Eight premenstrual records showed a significant increase in mean alpha frequency and 17 showed an increase in mean alpha amplitude. Theta activity and mild paroxysms were twice as common in premenstrual records, as was an abnormal response to hyperventilation. These findings may correlate with subjective mood changes commonly experienced in the premenstrual phase and in the well-recognized tendency of certain epileptic women to have seizures only at the time of their menses. It is suggested that when reporting on the EEGs of female subjects, cognizance should be taken of the stage reached in the menstrual cycle at the time of recording.