MR Changes in the Calcarine Area Resulting From Retinal Degeneration

Abstract

PURPOSE:To study MR images for atrophic changes in the calcarine area resulting from retinal degeneration. METHODS: MR images from nine patients with retinal degeneration confirmed by ophthalmologic examination and from 30 healthy volunteers were reviewed. The causes of retinal degeneration were hereditary pigmentary degeneration of the retina (four patients), high myopia (two patients), and chorioretinal atrophy (three patients); all patients had visual disturbances and visual field abnormalities. To estimate the morphological changes of the calcarine area, the widths of the right and left calcarine fissures were measured on T1-weighted sagittal images and compared with images from age-matched control subjects. RESULTS: The calcarine fissures were significantly dilated in the patients with retinal degeneration. The anterior and middle points, which represent the peripheral visual field center, were more dilated than the posterior point. CONCLU-SION: The MR findings suggested calcarine atrophy related to retinal degeneration. Transneuronal degenerative changes may occur in the calcarine area after retinal degeneration. The visual pathway from the retina to the striate cortex consists of three fibers. The first neuron contains a layer of bipolar and ganglion cells in the retina, the second neuron connects the ganglion cell layer and the lateral geniculate body, and the third neuron connects the lateral geniculate body and the striate cortex. Many earlier studies have shown that these neuroanatomic characteristics produce histologic changes in specific regions of the visual pathway, defined as transneuronal degeneration, caused by lesions of the retina and optic nerve (1, 2). Other studies have shown that distinct histologic changes in the visual cortex occur after removal of an eye, and that degeneration of the retina occurs after occipital ablation in animals (3, 4). Similarly, it is thought that histologic changes in the striate cortex appear as a consequence of retinal degeneration in humans. The purpose of this study was to evaluate the magnetic resonance (MR) imaging findings in the calcarine area resulting from retinal degeneration. Materials and MethodsMR images were reviewed in nine patients (four women and five men; 52 to 80 years old; mean age, 69 years) with retinal degeneration confirmed by ophthalmologic examination and in 30 age-matched healthy volunteers (eight women and 22 men; 50 to 84 years old, mean age, 68 years). The causes of retinal degeneration were hereditary pigmentary degeneration of the retina (four patients), high myopia (two patients), and chorioretinal atrophy (three patients). All patients had visual disturbances and visual field abnormalities. One patient was examined on a 0.5-T superconductive MR unit, and the remaining eight patients and all the volunteers were studied on a 1.5-T unit. The sagittal T1-weighted MR images were obtained using a spin-echo sequence with imaging parameters of 450 -

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