[Value of visual evoked potentials (VEP) in compression of the anterior visual pathway, especially in the area of the chiasm].

We investigated 86 patients by pattern half-field stimulation presenting clinically with temporal field-defects or with a mass causing compression of the visual pathways found by C.T.-scanning. Pattern half-field stimulation proved to be a very sensitive method for detecting a compression of the anterior visual pathways. In 65 cases the results of perimetry and VEP were congruent, 6 times the evoked potential was pathologic the perimetry showing no abnormalities, only 1 false negative VEP was observed. Thus we stress the importance of an investigation by VEP including half-field stimulation in all patients with suspected compression of the anterior visual pathways.