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Show University of Alabama at Birmingham, Birmingham, Alabama Supported in part by an unrestricted grant from the Research to Prevent Blindness, Inc, New York, NY. The author report no conflicts of interest. REFERENCES 1. Siddiqui JD, Loeffler JS, Murphy MA. Radiation optic neuropathy after proton beam therapy for optic nerve sheath meningioma. J Neuroophthalmol 2013;33: 165-168. 2. Vaphiades MS. Disk edema and cranial MRI optic nerve enhancement: how long is too long? Surv Ophthalmol. 2001;46:56-58. Response We thank Dr. Vaphiades for his interest in our article and agree that the etiology of optic nerve enhance-ment may be difficult to distinguish based on magnetic resonance imaging (MRI) findings alone. With an optic nerve sheath meningioma (ONSM), the tumor typically shows gadolinium enhancement rather than the nerve itself, giving rise to the typical tram-track sign, while with radi-ation optic neuropathy (RON), the optic nerve itself enhances and may therefore be indistinguishable from the enhancement of the surrounding ONSM. In our patient, we noted several features that supported the diagnosis of RON. Radiographically, the area of new optic nerve enhancement corresponded to the exact location of the highest proton beam radiation dose. Although the optic nerve showed normal short T1 inversion recovery signal at the time of the initial ONSM diagnosis, it showed increased signal with proximal enhancement at the time the patient presented with visual loss, which began 27 months after completion of radiation therapy. Diffuse enhancement of the nerve was noted such that it could not be separated from the surrounding sheath, as opposed to clear tram-track enhance-ment of the remaining distal nerve. Clinically, it would be unusual for an ONSM to grow rapidly, causing progressive visual loss over a period of days to weeks, and then remain stable for the next year, as in our patient. The onset of symptoms in our patient likewise fell within the typical time course for RON. We hope that these details help to further clarify the diagnosis of RON in our patient. The above findings were included in our original submission but were then omitted through the editing process. Jamal D. Siddiqui, MD Department of Ophthalmology, Rhode Island Hospital, Providence, RI Jay S. Loeffler, MD Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA Marjorie A. Murphy, MD Department of Ophthalmology, Providence Veterans Affairs Medical Center, Providence, RI Recurrent Third Nerve Palsy as the Presenting Feature of Neurofibromatosis 2 We read with interest the case report (1) describing recurrent third nerve palsy as the presenting feature of neurofibromatosis type 2 (NF2). We evaluated a child with similar clinical findings. Our patient, whose mother has NF2, presented at age 5 years with painless, right-sided ptosis, and upgaze palsy, with normal pupils that evolved over several days. There was no history of preceding illness or trauma. The remainder of the general and neurological examinations was normal. Hema-tological and biochemical screening as well as inflammatory markers were negative. Magnetic resonance imaging (MRI) of the brain with contrast was normal. The child remained otherwise well and his findings completely resolved over 6 weeks. Over the next 3 years, he had 3 identical spontaneous episodes all involving the same eye, with good but incomplete recovery, in that mild ptosis (1-2 mm) and diplopia on upgaze persisted. Repeat contrast-enhanced brain MRI with each episode was normal, as were blood studies including acetylcholine receptor antibodies for myasthenia gravis. 102 Letters to the Editor: J Neuro-Ophthalmol 2014; 34: 95-104 Letters to the Editor Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. At the age of 7 years, left hand weakness developed due to nerve sheath tumors affecting the roots of C8 and T1. Genetic testing confirmed the diagnosis of NF2. We agree with Barrett et al that there is no clear explanation for the recurrent third nerve palsy, but that it can be a presenting symptom of NF2 in children. Manish Prasad, MBBS, MD, MRCPCH Dewsbury District Hospital, Dewsbury, United Kingdom Jessy Choi, MBChB, FRCOpth Department of Paediatric Opthalmology Peter Baxter, MBBS, MRCPCH Department of Paediatric Neurology, Sheffield Children's Hospital, Sheffield, United Kingdom The authors report no conflicts of interest. REFERENCE 1. Barrett VJM, Tan MH, Elston JS. Recurrent third nerve palsy as the presenting feature of neurofibromatosis type 2. J Neuroophthalmol. 2012;32:329-331. Utilizing Optical Coherence Tomography in Diagnosing a Unique Presentation of Chiasmal Hypoplasia Variant of Septo-Optic Dysplasia We evaluated a patient whose findings relate to 2 recent reviews in the Journal, that of Borchert (1) on optic nerve hypoplasia and Fraser et al (2) dealing with nonglau-comatous optic disc cupping. A 13-year-old adopted boy was referred for abnormal optic nerve appearance. On examination, the visual acuity was 20/20 in each eye and intraocular pressure was 13 mm Hg, right eye, and 14 mm Hg, left eye. Funduscopy revealed bilateral excavated and pale optic nerves (Fig. 1). Retinal nerve fiber layer (RNFL) analysis by spectral-domain optical coherence tomography showed a pattern consistent with bow-tie atrophy in each eye (Fig. 2). Automated visual field testing revealed bitemporal hemianopia. Magnetic resonance imaging (MRI) of the brain was remarkable for absence of septum pellucidum and chiasmal atrophy (Fig. 3). Based on these findings, the diagnosis of chiasmal hypoplasia-variant septo-optic dysplasia (SOD) was made. Our patient presented with optic nerve cupping, raising suspicion for juvenile open-angle glaucoma. However, the RNFL analysis revealed thinning of nasal and temporal quadrants, unlike glaucomatous damage, which typically involves thinning of the superior and inferior quadrants. The relatively preserved superior and inferior RNFL bundles on optical coherence tomo-graphic analysis correlated well with the findings of bitemporal hemianopia and the MRI findings of chias-mal hypoplasia. To our knowledge, this is the first description of RNFL analysis in the chiasmal hypoplasia variant of SOD. This FIG. 1. Optic discs show thinning of the nasal and temporal rims, consistent with bow-tie optic atrophy. Letters to the Editor: J Neuro-Ophthalmol 2014; 34: 95-104 103 Letters to the Editor Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. |
