[Impairment of visual pathway function in right hemisphere in patients with arteriovenous malformation of the parietooccipital area of left hemisphere].

Marked arteriovenous malformation in the left parietooccipital area manifested only by symptoms of associative migraine involving changes of visual fields indicative of impaired functions of symmetrical compartments of the other brain hemisphere. Visual evoked potentials were changed in this patient because of dysfunction of both hemispheres and largely because of disorders in brain structures symmetrical to the site of arteriovenous malformation. This can be regarded as a manifestation of the so-called stealing phenomenon, when blood supply to one brain compartment is decreased because of excessive blood delivery to other regions of the brain. The results permit us to hypothesize regulation of blood supply to symmetrical compartments of brain hemispheres.