The occipital The occipital lobes Occipital lobe - Mahidol University

23/06/541. Deficits associated with lesions (cont)-Toxic states may produce transitions fromvisual distortion to blindness and backagain.- Eye movement may be affected differen-tially by right or left occipital lesions; leftlesions will shift to compensate for ascotoma while right lesions may not followin the area of the scotoma.1. Deficits associated with lesions(cont)- Left occipital lesions with involvementof the splenium of the corpus callosummay result in alexia without agraphia.- Focal seizures consisting of visualsensations have been associated withlesions found in area 17.NEUROPSYCHIATRY 121NEUROPSYCHIATRY 122NEUROPSYCHIATRY 123 NEUROPSYCHIATRY 1242. Tests for dysfunction-Perimetry allows definition of limits ofscotoma. Harms perimeter allowsdefinition in terms of contour, spectralvalues, intensity , as well as critical flickerfrequency.-Amblyopias may also be tested with Harmsperimeter; deficits are found in criticalflicker frequency, dark adaptation, and twopoint resolution.2. Tests for dysfunction (cont)-Homonymous hemianopsia indicates corticallesion or interruption of optic radiations, whilebitemporal hemianopsia indicates interruptionof the optic pathway at the optic chiasm.-Monocular blindness results from unilateraldestruction peripheral to the chiasm, andquadrantonopsia from selective interruption ofthe radiation fibers in one hemisphere, eithertemporal or nasal but not both.NEUROPSYCHIATRY 125NEUROPSYCHIATRY 12621