POSITIVE SPONTANEOUS VISUAL PHENOMENA LIMITED TO THE HEMIANOPIC FIELDIN LESIONS OF CENTRAL VISUAL PATHWAYS

We prospectively studied 32 patients with ischemic infarction of the r etrochiasmal visual pathways. Positive spontaneous visual phenomena (P SVP) in the blind hemifield were present in 13 patients (41%). The PSV P were subdivided into phosphenes, photopsias, visual hallucinations, palinopsia, and agitated delirium with hemianopia. PSVP were never ass ociated with auditory or other sensory positive phenomena, except in p atients with agitated delirium. Patients with photopsias, phosphenes, palinopsia, and visual hallucinations had similar lesions in MRI/CT, s uggesting no anatomic area unique for these four phenomena. However, t here was a significant difference in the severity of associated neurol ogic deficits between hemianopic patients with and without PSVP. Large r lesions destroying anteriorly located visual association areas precl uded the development of PSVP, which may be related to release from inh ibitory input of visual regions bordering the damaged area. Patients w ith the syndrome of agitated delirium and hemianopia had specific lesi ons involving the mesial aspect of the occipital lobe, the parahippoca mpal gyrus, and hippocampus.