Woman presents with unilateral, painless vision loss
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A 57-year-old woman was transferred to Lahey Hospital and Medical Center emergency department from a community hospital for an ophthalmology evaluation due to acute, painless vision loss in the left eye upon wakening that morning.
The patient denied any recent trauma, illness or change in medication. Her medical history was significant for hypertension, hyperlipidemia and type 2 insulin-dependent diabetes. She was a former smoker, having quit 2 years prior. Her ocular history was significant for presbyopia in both eyes, and the last dilated examination performed 1 year prior showed no documented abnormalities. Her family history was notable for age-related macular degeneration in her grandfather.
Source: Varsha Pramil, MD, and Kendra Klein-Mascia, MD
Examination
The patient’s visual acuity was 20/20 in the right eye and 20/800 with eccentric viewing in the left eye. The right pupil was round and reactive with no afferent pupillary defect. The left pupil was round and reactive with a positive afferent pupillary defect. Extraocular movements were intact bilaterally. Confrontation visual fields were full in the right eye and showed outer superior and nasal field restrictions in the left eye. IOP was within normal limits in both eyes. Anterior segment examination of both eyes showed no abnormal findings. On dilated fundus exam at bedside, there was concern for possible hyperemic disc with blurring of the nasal and inferior disc margins in the left eye. The retina and retinal vasculature were normal. Examination of the right eye showed no abnormalities.
The evaluation at the outside hospital included neurology consultation and neuroimaging with CT angiography of the head and neck, which showed no acute findings. In the emergency department, the patient’s blood pressure was mildly elevated to 150s/80s mm Hg, and her blood glucose level was elevated to 421 mg/dL. Serologies, including C-reactive protein, were normal. MRI of the brain and orbits with and without gadolinium was notable only for a few scattered foci of high T2/FLAIR signal intensity in the periventricular and subcortical white matter, most prominent in the right superior frontal gyrus, believed to be a nonspecific finding secondary to chronic microvascular disease.
Based on the ophthalmic exam and the unremarkable neuroimaging, the patient was presumed to have nonarteritic anterior ischemic optic neuropathy (NAION) with ophthalmology outpatient follow-up scheduled the following week. Over the next 3 days, however, the patient’s visual acuity in the left eye continued to deteriorate, and she presented urgently to the ophthalmology clinic. At this time, visual acuity had decreased to light perception in the left eye. She continued to deny ocular pain. Anterior segment and dilated fundus exams were normal in both eyes. Fluorescein angiogram (FA) showed mild nonproliferative diabetic retinopathy in both eyes. OCT of the macula, OCT of the retinal nerve fiber layer (RNFL) and color fundus photos (Figure 1) showed no abnormalities of the optic nerve or macula. Due to progressively worsening visual acuity, the patient was resent to the emergency department for repeat MRI of the brain and orbits with and without gadolinium.
The MRI showed new enhancement of the left optic nerve involving the intraconal portion of the left orbit with corresponding new faint increased T2 signal in the intraconal portion of the left optic nerve along with T2 flair hyperintense lesions with large juxtacortical right superior frontal gyrus lesion (Figure 2).
What is your diagnosis?
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Vision loss
In a patient with acute, unilateral, painless vision loss, the differential is broad. It is imperative to first rule out time-sensitive diagnoses such as arteritic anterior ischemic optic neuropathy or a retinal/cerebral ischemic event. This can be done with a thorough review of systems, lab work for inflammatory markers and neuroimaging. As initial bedside exam showed subtle disc edema and neuroimaging was unremarkable, the patient was initially diagnosed with likely NAION of the left eye. However, due to the rapid progression of vision loss, repeat MRI of the brain and orbits was recommended and showed hyperintense enhancement of the optic nerve and right superior frontal gyrus consistent with inflammatory demyelinating optic neuritis.
Clinical course
This patient was admitted for further workup and management. Given the rapid progression of vision loss, there was concern for neuromyelitis optica spectrum disorder (NMOSD) and myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease. Therefore, she was started on empiric treatment with intravenous 1 g methylprednisolone along with plasmapheresis. Lumbar puncture was done with cerebrospinal (CSF) studies showing oligoclonal bands present in CSF and serum with highly elevated basic myelin protein. MRI of the cervical and thoracic spine with and without contrast showed T2 hyperintense lesions of the left central cord at T9 consistent with chronic demyelination. Laboratory testing included negative hepatitis panel, negative MOG antibody, negative aquaporin-4 (AQP4) and neuromyelitis optica (NMO) IgG antibody, nonreactive Lyme antibody screen, nonreactive treponema pallidum IgG and IgM screen, negative antinuclear antibody screen, and normal angiotensin converting enzyme and IL-2. Exam findings along with imaging showing lesions in the brain and spine were consistent with a demyelinating disease, and the patient was diagnosed with left optic neuropathy in the setting of demyelinating disease, likely multiple sclerosis (MS). After completion of IV methylprednisolone and plasmapheresis treatment, she was discharged from the hospital with a plan to follow up in the MS clinic for outpatient management.
At 2-month follow-up, the patient’s visual acuity in the left eye recovered to counting fingers at 1 foot. On dilated fundus exam, there was diffuse pallor of the left optic nerve. Right eye examination continued to be normal with visual acuity of 20/20. Repeat MRI of the brain and orbits with and without gadolinium was stable with no new lesions. Repeat AQP4 and MOG/NMO testing was negative. She was started on ofatumumab therapy and will follow up with neurology and ophthalmology.
Discussion
Distinguishing between etiologies of optic neuropathy can be challenging. Characteristics to consider include speed of vision loss, pain with extraocular movements, appearance of the optic nerve, presence of an afferent pupillary defect, color vision testing and visual acuity. The above case highlights an example of an initial misdiagnosis of inflammatory optic neuritis as NAION.
Inflammatory optic neuritis can be infectious or noninfectious but is most commonly due to a demyelinating process, either idiopathic or secondary to a disease such as MS. It typically affects young patients and presents as an acute decrease in central vision associated with painful extraocular movements, but it can also be painless. On exam, optic disc edema is seen in one-third of these patients, color vision is often affected, and if unilateral or asymmetric, a relative afferent pupillary defect is present. Imaging typically identifies inflammatory, enhancing lesions in the brain and orbits. The correct protocol must be utilized in these cases. MRI of the brain and orbits with and without gadolinium and fat suppression protocol is necessary as fat along with enhancing lesions can appear bright on T1-weighted MRI sequences. If there is bilateral or severe and extremely progressive vision loss due to optic neuritis, testing for NMOSD or MOG-associated optic neuritis should be done. Treatment of optic neuritis requires high-dose IV steroids. Plasmapheresis is considered if optic neuritis is refractory to steroids or in cases of NMO or MOG-associated optic neuritis.
It is difficult to distinguish between cases of acute optic neuritis and NAION especially when patients present with painless vision loss with optic disc edema. One study reported an early altitudinal pattern of ganglion cell complex (GCC) thinning in acute NAION resulting in a significant difference in mean GCC thickness between the superior and inferior hemifields that was not present in cases of acute optic neuritis. Studies have also shown that patients with NAION typically progress to more severe RNFL thinning compared with optic neuritis in the chronic stages. However, in the emergency setting in which diagnostic ophthalmic imaging such as OCT is not readily accessible, a thorough history and examination are vital. It is important to understand that optic neuritis is typically characterized by diffuse vision loss or a central field defect compared with an altitudinal field defect in NAION. NAION is also unlikely to have poor visual acuity such as hand motion or worse, with only 50% of patients with NAION presenting with visual acuity worse than 20/60.
Without prompt diagnosis and treatment, vision can deteriorate, and systemic disease may be missed. On the other hand, optic neuritis is overdiagnosed in 60% of cases, and high-dose steroid therapy or plasmapheresis can lead to unnecessary side effects. Therefore, it is important to critically think about the patient’s symptoms and exam findings to avoid misdiagnosis and preventable side effects. Lastly, close follow-up is warranted as evolving vision loss may mandate reconsideration of an initial diagnosis.
- References:
- Alves JM, et al. Mult Scler Relat Disord. 2020;doi:10.1016/j.msard.2020.102337.
- Biousse V, et al. Lancet Neurol. 2016;doi:10.1016/S1474-4422(16)30237-X.
- Dattilo M, et al. Neuroophthalmology. 2020;doi:10.1080/01658107.2020.1785509.
- Erlich-Malona N, et al. Acta Ophthalmol. 2016;doi:10.1111/aos.13128.
- Rizzo JF 3rd, et al. Ophthalmology. 2002;doi:10.1016/s0161-6420(02)01148-x.
- Stunkel L, et al. JAMA Ophthalmol. 2018;doi:10.1001/jamaophthalmol.2017.5470.
- Winter A, et al. Semin Ophthalmol. 2020;doi:10.1080/08820538.2020.1866027.
- For more information:
- Edited by Jonathan T. Caranfa, MD, PharmD, and Angell Shi, MD, of New England Eye Center, Tufts University School of Medicine. They can be reached at jcaranfa@tuftsmedicalcenter.org and ashi@tuftsmedicalcenter.org.
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