[Chiasmatic syndrome--clinical value of the visual evoked responses (VER) to the diagnosis (author's transl)].

The VER is compared with that of other neuroophthalmological examinations in 25 patients presenting lesions of the anterior optic pathways (of which 18 were of an expansive nature). The authors believe that visual field plotting and VER are indispensable complementary examinations, giving results which orientate subsequent investigations towards a chiasmatic or prechiasmatic syndrome. In 15 cases of chiasmatic syndrome of tumoral origin (thus in 30 optic nerves), visual fields and VER showed early pathological changes. In originally unilateral forms, VER changes are usually bilateral even when visual field changes are still unilateral. This draws attention to the fact that some process may be injuring either both optic nerves, or the optic chiasma. In cases where the patients are too young, or collaboration is insufficient, to enable visual fields to be plotted, evolution may be studied by VER. In post-surgical follow-up, or during therapy (eg. irradiation), VER recuperation carries a good prognosis. If no VER improvement occurs the expansive process has caused irreparable optic nerve atrophy. Nevertheless, frequent visual field study remains the best diagnostic method of chiasmatic syndromes and their evolution. An earlier diagnosis may be made in the majority of cases by the dual study of visual fields and VER.