Visual evoked potentials in acute occipital blindness

Abstract

Pattern-evoked and flash-evoked responses were recorded from four patients with acute blindness due to occipital ischaemia. No responses could be obtained with pattern stimulation. Flash stimulation, however, yielded well-reproducible potentials in all four cases in spite of practically complete visual loss. In one patient vision recovered completely while the three others showed poor or minimal recovery in restricted visual field areas only. It is concluded that the flash method is not appropriate for differentiation of occipital blindness from psychogenic visual disorders. Furthermore, preserved flash-evoked potentials in the acute stage of occipital blindness cannot be taken as a reliable prognostic sign for visual recovery, as has been postulated by others. A possible extrastriate origin of these flash responses is discussed in view of recent theories on a second visual system.

Cortical visual impairment following bacterial meningitis: magnetic resonance imaging and visual evoked potentials findings in two cases

“…Also case 2 recovered residual visual functions such as subconscious spatial orientation. The recovery of some visual functions in patients with CVI and severe occipital brain damage raised the assumption of an additional extrastriate origin of these function [18,27]. Several authors believe this pathway to include retino-collicular-pulvinar-extrastriate cortical projections and to allow primitive subconscious visual functions such as spatial orientation [6,14,18,21,27] or recognition of movement [7].…”

Pattern visual evoked potentials in cases of ambiguous acuity loss

“…An objective measure of visual function is valuable for assessing infants [1] and adults with no visible distal damage to explain subjective reports of profound acuity loss. The differential diagnosis includes cortical blindness in which there is bilateral visual loss and normal pupillary responses [2][3][4][5][6][7][8], functional visual loss from either hysteria or malingering [9][10][11][12][13], early retrobulbar optic neuropathy before the development of optic nerve pallor [14] and retinal diseases such as paraneoplastic retinopathy where fundus changes may be mild [15]. While a relative afferent pupillary defect can be seen in early unilateral cases of optic neuropathy, this defect may not be apparent in bilateral cases.…”

Νευροψυχολογικοί Παράγοντες Που Επηρεάζουν Την Εκμάθηση Μητρικής Και Ξένης Γλώσσας

“…Επίσης, έχουν παρατηρηθεί αλλαγές στο ύψος και το λανθάνοντα χρόνο των οπτικών προκλητών δυναμικών μέχρι την ηλικία των 19 ετών και πάνω από την ηλικία των 50 ετών. Κάποιες έρευνες αναφέρουν ότι δεν υπάρχει αλλαγή στο λανθάνοντα χρόνο του Ρ100 από την εφηβεία μέχρι την ηλικία των 50 ετών και μετά αναφέρεται μια αύξηση από 2 μέχρι 5 msec ανά δεκαετία ( Allison et al 1979, Chiappa 1990, Hess et al 1982, Stockard et al 1979 ) O Kjaer ( 1980 ) βρήκε ότι ο λανθάνων χρόνος του Ρ100 σε άτομα ηλικίας 10 με 19 χρονών ήταν σημαντικά μεγαλύτερος απ' ότι στους ενήλικες. Οι Allison et al (1984 ) αναφέρουν προοδευτική μείωση του λανθάνοντα χρόνου από την ηλικία των 4 ετών μέχρι την ηλικία των 19 ετών, προτείνοντας ότι αλλαγές στο λανθάνοντα χρόνο παρατηρούνται μέχρι το άτομο να ενηλικιωθεί.…”