Positive spontaneous visual phenomena limited to the hemianopic field in lesions of central visual pathways.

We prospectively studied 32 patients with ischemic infarction of the retrochiasmal visual pathways. Positive spontaneous visual phenomena (PSVP) in the blind hemifield were present in 13 patients (41%). The PSVP were subdivided into phosphenes, photopsias, visual hallucinations, palinopsia, and agitated delirium with hemianopia. PSVP were never associated with auditory or other sensory positive phenomena, except in patients with agitated delirium. Patients with photopsias, phosphenes, palinopsia, and visual hallucinations had similar lesions in MRI/CT, suggesting no anatomic area unique for these four phenomena. However, there was a significant difference in the severity of associated neurologic deficits between hemianopic patients with and without PSVP. Larger lesions destroying anteriorly located visual association areas precluded the development of PSVP, which may be related to release from inhibitory input of visual regions bordering the damaged area. Patients with the syndrome of agitated delirium and hemianopia had specific lesions involving the mesial aspect of the occipital lobe, the parahippocampal gyrus, and hippocampus.