Subclinical Optic Neuritis in Neuromyelitis Optica

Using time domain OCT, Karam and Hedges (3) concluded that OCT could not be used to differentiate individuals with congenitally crowded optic nerves from individuals with mild papilledema. Conversely, Johnson et al (4) argued that OCT could be used to differentiate optic disc edema from optic nerve head drusen, but these authors included subjects with disc edema that was "mild, moderate, and severe" and drusen that were both visible and buried. These authors also included subjects with papille-dema, ischemic optic neuropathy, and optic neuritis in their study population. Lee et al (5) claimed that spectral domain OCT may be used to differentiate optic disc edema from optic nerve head drusen, but they also included subjects in whom the edema ranged from "subtle to severe," and did not state the etiology of the disc edema in their subjects. In the study by Sarac et al, the optic nerve head drusen group contained eyes with both visible and buried drusen. The optic disc edema group was also heterogeneous, containing subjects with "subtle to severe" optic nerve swell-ing. In addition, the optic disc edema group contained subjects with papilledema, nonarteritic anterior ischemic optic neuropathy, and optic neuritis. However, most clini-cians would have no difficulty distinguishing a patient with optic nerve head drusen from a patient with anterior ischemic optic neuropathy or optic neuritis. We do not dispute the results reported by Sarac et al. Our concern is that clinicians reading this article will inappropriately extrapolate these conclusions to clinical care. When faced with a patient in whom the differential diagnosis includes mild optic disc edema and buried optic nerve head drusen, the guidelines proposed by Sarac et al may not hold. Their study population was not relevant to the clinical question being asked. Currently, it appears that the conclusions reached by Karam and Hedges (3) still hold. Until a study is designed with a clinically relevant population of subjects, the ques-tion of the utility of OCT in the differential diagnosis of optic disc edema and optic nerve head drusen remains unanswered. Bradley J. Katz, MD, PhD Alison V. Crum, MD Kathleen B. Digre, MD Judith E. A. Warner, MD John A Moran Eye Center Department of Ophthalmology and Visual Sciences and Department of Neurology University of Utah Health Sciences Center Salt Lake City, Utah [e-mail] The authors report no conflicts of interest. Supported by an unrestricted grant to the Department of Ophthalmology and Visual Sciences by Research to Prevent Blindness, New York, NY. REFERENCES 1. Sarac O, Tasci YY, Gurdal C, Can I. Differentiation of optic disc edema from optic nerve head drusen with spectral-domain optical coherence tomography. J Neuroophthalmol. 2012;32:207-211. 2. Frisén L. Swelling of the optic nerve head: a staging scheme. J Neurol Neurosurg Psychiatry. 1982;45:13-18. 3. Karam EZ, Hedges TR. Optical coherence tomography of the retinal nerve fibre layer in mild papilloedema and pseudopapilloedema. Br J Ophthalmol. 2005;89:294-298. 4. Johnson LN, Diehl ML, Hamm CW, Sommerville DN, Petroski GF. Differentiating optic disc edema from optic nerve head drusen on optical coherence tomography. Arch Ophthalmol. 2009; 127:45-49. 5. Lee KM, Woo SJ, Hwang JM. Differentiation of optic nerve head drusen and optic disc edema with spectral-domain optical coherence tomography. Ophthalmology. 2011;118: 971-977. Subclinical Optic Neuritis in Neuromyelitis Optica We read with great interest the review of neuromye-litis optica (NMO) by Morrow and Wingerchuk (1). Even with proposed diagnostic criteria (2), establish-ing the diagnosis of NMO may be difficult. We describe a patient with white matter cerebral lesions, myelitis, and subclinical optic neuritis with negative NMO-IgG at the initial presentation. The diagnosis of NMO became cer-tain 5 months later when the patient developed overt bilateral optic neuritis and a positive NMO-IgG anti-body. A 46-year-old woman experienced the onset of dizzi-ness, nausea, and vomiting. Neurological examination was unremarkable except for horizontal gaze evoked nystagmus and mild weakness in her right leg. Muscle strength in the right lower extremity was at 4/5, patellar deep tendon reflexes were hypoactive, and the plantar reflex was indifferent on the right side. Vision was 20/20 bilaterally with normal color vision, funduscopy, and visual evoked potentials. Automated visual fields demonstrated mild generalized depression (Fig. 1). Brain magnetic resonance imaging (MRI) revealed enhancement of the entire length of the left optic nerve (Figs. 2A and 2B) hyperintensities in the dorsal medulla, around the fourth ventricle, in the periaqueductal gray matter, mammillary bodies, the thalamus, and in the vi-cinity of the third ventricle (Fig. 2C). MRI of the spine Letters to the Editor: J Neuro-Ophthalmol 2013; 33: 202-207 205 Letters to the Editor Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. showed T2 hyperintensity extending through cervical and thoracic spinal cord (Fig. 2D). Serum biochemistries, complete blood count, and erythrocyte sedimentation rate were normal, as were serological tests for herpes virus family, cytomegalovirus, Epstein-Barr virus, antinuclear antibody, anti-Smith antibody, anti-soluble substance-A and anti-soluble substance-B, anti-Jo-1, anti-Scl-70 anti-body, anticardiolipin antibodies, and NMO-IgG. Cerebrospinal fluid was acellular, without oligoclonal bands, normal glucose, and increased protein of 271 mg/dL (normal, 15-45 mg/dL). The patient was treated intravenously with 1,000 mg of methylprednisolone/day for 7 days. She returned to our clinic 5 months later with pain in the right eye and blurred vision in both eyes. Visual acuity was 20/50 in the right eye, and 20/200 in the left eye. The right optic disc was swollen, and the left disc was pale. Visual evoked potentials were abnormal bilaterally, and NMO-lgG antibody was now found to be positive. Our case is instructive for 2 reasons. First, patients with NMO may present with clinical and neuroimaging findings highly suggestive of NMO, yet NMO-IgG antibody may not be detected. Given that the sensitivity of this test is 73% (3), repeat testing is warranted if clinical suspicion is high and initial results are negative. Second, patients with NMO may present with subclinical optic neuropathy. At presentation, our patient only had mild visual field changes, yet MRI revealed contrast enhancement of the left optic nerve. To our knowl-edge, this observation has not been reported previously. Durdane Aksoy Department of Neurology, Gaziosmanpasa University Faculty of Medicine, Tokat, Turkey, [e-mail] Erkan Gokce Department of Radiology, Gaziosmanpasa University Faculty of Medicine, Tokat, Turkey Semiha Kurt Department of Neurology, Gaziosmanpasa University Faculty of Medicine, Tokat, Turkey Betul Cevik Department of Neurology, Gaziosmanpasa University Faculty of Medicine, Tokat, Turkey Helin Deniz Demir Department of Ophthalmology, Gaziosmanpasa University Faculty of Medicine, Tokat, Turkey FIG. 1. Visual fields show mild generalized loss bilaterally (mean deviation: right, 23.83 dB; left, 24.44 dB). 206 Letters to the Editor: J Neuro-Ophthalmol 2013; 33: 202-207 Letters to the Editor Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. REFERENCES 1. Morrow MJ, Wingerchuk D. Neuromyelitis optica. J Neuroophthalmol. 2012;32:154-166. 2. Wingerchuk DM, Lennon VA, Pittock SJ, Lucchinetti CF, Weinshenker BG. Revised diagnostic criteria for neuromyelitis optica. Neurology. 2006;66: 1485-1489. 3. Lennon VA, Wingerchuk DM, Kryzer TJ, Pittock SJ, Lucchinetti CF, Fujihara K, Nakashima I, Weinshenker BG. A serum autoantibody marker for neuromyelitis optica: distinction from multiple sclerosis. Lancet. 2004;364:2106-2112. FIG. 2. Contrast-enhanced T1 axial (A) and coronal (B) magnetic resonance imaging (MRI) shows enhancement of the left optic nerve (arrows). C. Axial fluid-attenuated inversion recovery image demonstrates an increased signal (arrows) surrounding the third ventricle. D. Sagittal T2 MRI of the spine shows a longitudinally extensive lesion from the medulla to the thoracic cord. Letters to the Editor: J Neuro-Ophthalmol 2013; 33: 202-207 207 Letters to the Editor Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited.