Own Study

Electroencephalogram

The curves were registered with a Kaiser or Grass electroencephalograph, with the 10-12 electrode system recommended by the International Federation, and conventional leads. First tracings were led off for about 30 minutes with the subject resting, then for a period with the patient overbreathing, and lastly during photostimulationon with the Kaiser stroboscope, in most cases according to the method described by Selld6n (1964).

Whenever the patients had undergone more than one EEG examination, their elect roencephalographic characteristics were judged from the record taken in connection with the present study. The EEG could not be taken in I case for technical reasons, and I subject was not tested with photostimulation because this had caused an epileptic fit when it was done before.

The curves were classified as normal, borderline or abnormal, according to the criteria used routinely at the Neurophysiologic Department at the Neurologic Department of the G6teborg University. A normal record, according to these criteria, is characterized by an alpha rhythm with a frequency of 8-13 c/s interspersed with varying amounts of beta rhythm; if any activity between 5-7 c/s is present, it should not take up more than 10 to 15 per cent of the record, and be distributed symmetrically, or almost symmetrically, over the two hemispheres, and have the same amplitude as the alpha rhythm; this corresponds to the oneplus category in a three stage classification (e.g., Frey & Steinwall, 1953).

In the following tabulation the alpha frequency was taken as the average in four one-second sections of the tracings from the temporooccipital leads. The term paroxysmal activity covers both sharp waves and spikes and bursts of low-frequency waves with an amplitude at least twice that of the background activity, and focus covers abnormal activity over a limited region, or mostly over a limited region. The response to hyperventilation was considered abnormal when high waves with a frequency of 3 c/s appeared within the first two minutes and persisted more than 30 seconds after the sub ect stopped over-breathing.
The results were as follows:

No record showed anything of note in regard to beta rhythm, and none showed any rhythmic delta activity. One record showed a focus of abnormal activity in the right occipital region, another in the right temporal region and another in the left fronto-temporal region.

Eight of the subjects with abnormal EEG's were men (cases 4, 7, 12 13, 15, 16, 19, 29) and 4 women (cases 31, 33, 38, 42), which is a sex ratio about corresponding to that in the whole series. Six of these were getting contrary sex hormones at the time their EEG's were taken, and 5 of the 30 with normal records were getting these hormones. None were getting any drugs which affect the EEG. Whether the administration of sex hormones has any effect on the EEG is not known, but the foregoing figures do not point in that direction.