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Show PHOTO ESSAY Ipsilateral Wallerian Degeneration of the Distal Optic Radiations After Infarction at Their Root Mi Young Oh, MD, Jeong-Min Hwang, MD, Yun Joong Kim, MD, and Ji Soo Kim, MD FIG. 1. A. Axial T2 MRI at two levels discloses a round high signal area involving the root of the right optic radiations (arrow) and a strip of high signal running along the ipsilateral optic radiations in their course toward the striate cortex (arrowheads). These findings are consistent with infarction of the proximal optic radiations, perhaps from occlusion of the anterior choroidal artery, and Wallerian degeneration of the more distal optic radiations. B. Visual field examination demonstrates a left homonymous inferior quadrantanopia corresponding to the right optic radiation signal abnormality. Department of Neurology (MYO, JSK) and Ophthalmology (J-MH), Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seoul, Korea; and ILSONG Institute of Life Science (YJK), Department of Neurology, Hallym University Sacred Heart Hospital, Hallym University, Chuncheon, Korea. This work was supported by Grant 03-2007-002 from the Seoul National University Bundang Hospital Research Fund. Address correspondence to Ji Soo Kim, MD, Department of Neurology, College of Medicine, Seoul National University, Department of Neurology, Seoul National University Bundang Hospital 300 Gumi-dong, Bundang-gu, Seongnam-si, Gyeonggi-do, 463-707, Korea; E-mail: jisookim@snu.ac.kr 1 4 6 J Neuro-Ophthalmol, Vol. 29, No. 2, 2009 Wallerian Degeneration J Neuro-Ophthalmol, Vol. 29, No. 2, 2009 Abstract: A 54-year-old man who developed a left homonymous inferior quadrantanopia showed MRI findings of infarction of the proximal portion of the right superior optic radiations and high T2 signal along the entire distal course of the ipsilateral optic radiations consistent with Wallerian degeneration. Frequently reported in other settings, this imaging abnormality has rarely been described in anterior optic radiation lesions. (J Neuro-Ophthalmol 2009;29:146-148) A54-year-old man was found to have a left homony-mous inferior quadrantanopia during evaluation of the complaint of blurred vision present for several months. He had essential hypertension treated with antihypertensive medication. Results of a review of his systems were negative. Brain MRI, performed 4 months after the initial detection of the visual field loss, revealed features con-sistent with infarction of the right proximal portion of the optic radiations near the lateral geniculate body, and ipsilateral Wallerian degeneration of the optic radiations extending posteriorly to the striate (primary visual and calcarine) cortex (Fig. 1A). Our examination confirmed the visual field defects (Fig. 1B) with normal visual acuity, color vision, ocular motility and alignment, pupillary size and reactivity, and ophthalmoscopy. The neurologic examination was other-wise normal. The optic radiations connect the lateral geniculate body with the ipsilateral striate cortex (Fig. 2). The radia-tion fibers conveying visual information for the superior visual field quadrants sweep around the temporal horn of the lateral ventricle to form Meyer's loop. The fibers serving the inferior visual field quadrants course directly backward to the striate cortex (1). The fact that the visual field defect in our patient was mostly confined to the left inferior quadrant indicates damage to the superior portion of the optic radiations, possibly due to occlusion of the anterior choroidal artery (2). Wallerian degeneration refers to antegrade distal degeneration of the axon and its myelin sheath resulting from damage to the proximal portion of the axon itself or its cell body (3). Wallerian degeneration becomes evident on T2 MRI as a hypointense signal usually 4 weeks after infarction and turns into a hyperintense signal 6-10 weeks later (3). Diffusion imaging may detect Wallerian de-generation earlier than T2 MRI (4,5). FIG. 2. Location of the lateral geniculate body (curved arrow) and optic radiations (straight arrow) in the corresponding axial slices of a normal brain. 147 Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. J Neuro-Ophthalmol, Vol. 29, No. 2, 2009 Oh et al Wallerian degeneration has been reported on MRI in various diseases (6,7), but most often in patients with stroke involving the corticospinal tract (3,8). In contrast, reports on Wallerian degeneration of the optic radiations have been sparse (9,10). It was first described in a single report describing a patient with an arteriovenous malformation and a patient with metastatic sarcoma involving the lateral geniculate body (9). A T2 hyperintense layer was observed in the external sagittal striatum in another patient with an old infarction extending from the lateral geniculate body to the occipital lobe (10). Although mentioned in the reports, the visual field defects were not displayed in those reports (9,10). This is the first documentation of visual field defects associated with Wallerian degeneration of the optic radiations in a patient with presumed stroke involving the proximal portion of the optic radiations. More careful scrutiny of MRI studies may disclose this finding. REFERENCES 1. Nolte J, ed. The Human Brain: An Introduction to Its Functional Anatomy. 5th ed. St. Louis: Mosby; 2002. 2. Trobe JD. The optical, retinocortical and integrative components. In: Trobe JD, ed. Neurology of Vision. New York: Oxford University Press Inc; 2001:5-42. 3. Kuhn MJ, Mikulis DJ, Ayoub DM, et al. Wallerian degeneration after cerebral infarction: evaluation with sequential MR imaging. Radiology 1989;172:179-82. 4. 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Kitajima M, Korogi Y, Takahashi M, et al. MR signal intensity of the optic radiation. AJNR Am J Neuroradiol 1996;17: 1379-83. 148 © 2009 Lippincott Williams & Wilkins Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. |
