Journal of Neuro-Ophthalmology:
Homonymous Hemimacular Thinning: A Unique Presentation of Optic Tract Injury in Neuromyelitis Optica
Romero, Rebecca S. MD; Gutierrez, Ismael BS; Wang, Eugene MD; Reder, Anthony T. MD; Bhatti, M. Tariq MD; Bernard, Jacqueline T. MD; Javed, Adil MD, PhD
Department of Neurology (RSR, IG, EW, ATR, JTB, AJ), University of Chicago, Chicago, Illinois; and Departments of Ophthalmology and Medicine, Division of Neurology (MTB), Duke Eye Center and Duke University Medical Center, Durham, North Carolina.
Address correspondence to Adil Javed, MD, PhD, Department of Neurology, University of Chicago, 5841 South Maryland Avenue, MC 2030, Chicago, IL 60637; E-mail: email@example.com
Supported by Biogen grant US-TYS-09-10019 (Bernard) and fellowship funds from Teva Pharmaceuticals and National Multiple Sclerosis Society (Romero).
Dr Romero has received honoraria for speaking engagements from Bayer Healthcare, Teva Pharmaceuticals, and Novartis. She also received fellowship support from Teva Pharmaceuticals. Dr Bhatti has served as a consultant and is on the speaker bureau for Bayer healthcare, Pfizer, Serono, and Novartis. Dr Bernard is on the speaker bureau for Novartis and Bayer and consultant for Biogen. Dr Javed has served as a consultant and is on the speaker bureau for Bayer HealthCare, Biogen, Teva Pharmaceuticals, Serono, Novartis, and Questcor. Dr Reder has served as a consultant and is on the speaker bureau for Bayer Schering Pharma AG/Bayer HealthCare Pharmaceuticals, Biogen, Hoffman La Roche, Merck-Serono, Novartis, Sanofi-Aventis, Serono Symposia, and Teva Pharmaceuticals. Mr Gutierrez and Dr Wang have nothing to disclose.
Abstract: A 42-year-old African American woman with a 5-year history of neuromyelitis optica was found to have an incongruous homonymous hemianopia. Optical coherence tomography (OCT) showed corresponding left homonymous hemimacular thinning. Magnetic resonance imaging of the brain demonstrated a demyelinating lesion in the left optic tract (OT) just anterior to the lateral geniculate nucleus and diffusion tensor magnetic resonance tractography confirmed axonal fiber loss in the left OT. This case illustrates the complementary and confirmatory roles of visual field testing, macular OCT, and neuroimaging in an OT lesion, which caused selective hemimacular thinning through retrograde degeneration.
We report the novel appearance of hemimacular thinning on optical coherence tomography (OCT) from an optic tract (OT) lesion, causing an incongruous homonymous hemianopia in a patient with neuromyelitis optica (NMO).
A 42-year-old African American woman presented with longitudinal extensive transverse myelitis (LETM) causing weakness and numbness in her lower extremities. She was treated with intravenous methylprednisolone followed by a tapering course of oral prednisone and was left with residual lower extremity paresthesias. Ten months later, she had relapse of transverse myelitis accompanied by bilateral optic neuritis. Positive NMO-IgG serology confirmed the diagnosis of NMO. She was treated again with steroids and subsequently given intravenous rituximab (1 g) at 2-week intervals. She had repeat cycles of rituximab about every 6–9 months over 3 years and then was switched to low-dose oral prednisone and mycophenolate mofetil. Since her last exacerbation, she has not had any major relapse while maintained on prophylactic therapy.
Four years after symptom onset, the patient's visual acuity was 20/15 bilaterally and she remained neurologically stable. Because of persistent complaint of visual impairment, she underwent further evaluation. Automated visual fields (Humphrey Visual Field Analyzer II 30-2 SITA Standard Program) showed an incongruous right homonymous hemianopia (Fig. 1). Macular OCT demonstrated significant thinning of the left temporal and right nasal portions of the macula, that is, left homonymous hemimacular thinning (Fig. 2). The total macular volume was reduced bilaterally in the NMO patient, right 7.02 mm3 and left 6.67 mm3, compared with the healthy controls (95% confidence interval, 8.55–8.89 mm3). The global mean retinal nerve fiber layer (RNFL) thickness was 69 μm in the right eye and 68 μm in the left eye (controls, 97 μm). Peripapillary RNFL thinning on OCT was found primarily in the temporal quadrant of each eye (Fig. 3). Despite this finding, bowtie optic atrophy was not detected on funduscopic examination.
MRI of the brain revealed atrophy of the left OT compared with the right (Fig. 4A, B). A demyelinating lesion was detected in the region of the left OT (Fig. 4C), and diffusion tensor imaging (DTI) with tractography confirmed involvement of the OT (Fig. 4D). To gauge the degree of tissue loss in the left OT in our patient, further DTI measures were derived, including fractional anisotropy (FA). FA describes directionally restricted diffusion of water and thus decreased FA values are characteristic of demyelinating lesions and other forms of injury (1). There was a significant decrease in the number of fibers originating from the left OT (Fig. 5A), and mean FA value in the left OT was also reduced compared to contralateral OT in our patient and healthy controls (Fig. 5B). The mean FA value of the whole thalamus was similar in the NMO patient and healthy subjects, reinforcing that the lesion was anterior to the thalamus (data not shown). Tractography and FA analyses on the diffusion imaging was done using FMRIB's Diffusion Toolbox as has been previously described (http://www.fmrib.ox.ac.uk/fsl/index.html) (2). To assess whether disruption in the anterior visual pathway resulted in alterations in the posterior visual pathways, pericalcarine cortex thickness was analyzed using automated computational tools (FreeSurfer software) (3). No discernable changes were observed in the pericalcarine cortical thickness in our patient compared with the contralateral side or healthy controls (Fig. 5C) nor were there any changes in the FA values (data not shown).
In our patient with NMO, a demyelinating lesion in the OT produced selective thinning in the macula of each eye in a pattern consistent with a homonymous hemianopia. This abnormality detected by OCT is probably due to loss of ganglion cell bodies and their axons through retrograde degeneration (4,5). Thinning of the affected OT on MRI is consistent with this observation, and diffusion-tensor tractography confirmed the anatomic relationship of demyelinating lesion with the OCT.
There was also diffuse reduction in the RNFL of each eye. The previous episode of bilateral optic neuritis was the likely cause of this OCT finding.
Our case is an example of visual field OCT–MRI–DTI tractography correlation. It demonstrates the growing number of imaging modalities available to the clinician in localizing and characterizing neuro-ophthalmic disease.
The authors thank the patient who took part in this case report; they also thank Nancy Arndt, RN, MSCN, for patient education.
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This article has been cited 3 time(s).
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