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April 17, 1987

Visual Hallucinations: More Diagnoses

Author Affiliations

Society for Neurovascular Surgery Oak Park, Ill

Society for Neurovascular Surgery Oak Park, Ill

JAMA. 1987;257(15):2035-2036. doi:10.1001/jama.1987.03390150051029

To the Editor.—  In the discussion of visual disorientation of short duration in a patient with right-sided hemiplegia and hemianopsia,1 consideration of hemodynamics at the level of the circle of Willis was omitted. If the patient had occlusion of the left internal carotid artery with a patent left posterior communicating artery, transient occipital lobe ischemia may have been produced by a transient reduction of blood flow in the dominant vertebral artery. This may have been due either to mechanical obstruction of the vertebral artery (eg, as a function of head position) or to a reduction in cardiac output (eg, as a result of the upright position, Valsalva's maneuver, or cardiac dysrhythmia).If the internal carotid artery is occluded and if vertebral angiography shows filling of both the anterior and posterior circulation, brain ischemia with functional impairment is common. Blood flow in the vertebral artery can be maximized by a