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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. |
