Stationary Potential of the Brain : Part II. Clinical Studies
Stationary potential changes through the scalp and those on the cortex were measured by a high impedance chopper stabilized DC amplifier and calomel half-cell electrodes. For clinical use, a new SP encephalograph was devised. It can detect SP changes at 90 points automatically. SP encephalogram in normal subjects shows a symmetrical voltage distribution over the hemisphere with the highest potential in the vertex (ranging from 10 to 20 mV when the reference electrode was on the nasion).
... he nasion). Clinical studies in 345 cases and intraoperative SP measured in 28 cases together with supplemental animal experiments indicated that if the lesion involves the cortex, the SP over the area shows negativity as compared with the normal portion on the order of 5-20 mV, whereas if the lesion is in the subcortex, the cortex over the lesion shows positivity on the order of 5-10 mV. The polarity of SP change is decided by the relationship -between the location of the lesion to the cortex. If the lesion is an expanding type such as meningioma, the SP shows "crateriform potential change ," that is, negative in the center of the tumor and positive surrounding it. Slight cortical compression also exhibits slight positivity. Based on the above-mentioned principle of SP change, SP encephalography may be of help in estimating the area, depth, degree and nature of the lesion.