Written by: Steve Chukwulebe, MD (NUEM PGY-4) Edited by: Victor Gappmaier, MD (NUEM Alum ‘18) Expert commentary by: Shira Simon, MD, MBA
Case:
31-year-old female, with no significant past medical history, presents to the emergency department with a mild headache and blurry, decreased vision in the right eye for the past 2 days. Other historical elements include that the patient has been experiencing pain with eye movement. However, she denies difference in color perception. She also denies any trauma to the eye, recent fevers, chills, malaise, exposures, or travel. The left eye is unaffected.
Exam:
Normal vitals and a well appearing female of stated age
Ocular exam reveals normal appearing eyes without chemosis, proptosis, conjunctival injection, scleritis, icterus, or foreign bodies
Non-dilated funduscopic exam is unremarkable
Visual acuities are OD: 20/40 and OS: 20/20
Tonometry reveals right and left eye pressures are < 20 mmHg
Slit lamp exam is without cells or flare
Fluorescein stain is without any corneal uptake
CN 3-12 are intact, and no focal neurologic deficits on exam
Differential Diagnosis [1,2]:
Painless Vision Loss
Central retinal artery occlusion
Central retinal vein occlusion
Retinal detachment
Vitreous detachment/vitreous hemorrhage
Tumor/Mass
Stroke
Painful Vision Loss
Acute angle closure glaucoma
Scleritis
Anterior uveitis (iritis)
Optic neuritis
Keratitis
Corneal abrasion/trauma
Temporal arteritis
The challenge in diagnosing optic neuritis is to exclude other causes of acute monocular vision loss. Therefore, a normal appearing eye, slit lamp exam, fluorescence stain, and intraocular pressures eliminates scleritis, uveitis, keratitis/abrasion, and glaucoma respectively [5]. Additionally, the history is less suggestive of other urgent and emergent ocular pathologies such as retinal detachment and central retinal artery occlusion.
Some physical exam findings more specific to optic neuritis include:
Afferent pupillary defect
Optic disk swelling and papilledema, which can be seen by ultrasound [6]
Decreased perception in the saturation of deep red colors
Decreased visual acuities ranging from 20/25 to 20/190, and even no light perception[4]
Eye pain, especially with eye motion, is seen in 92 percent of patients
Loss of color vision out of proportion to the decrease in visual acuity
Retro-orbital headache
Further diagnostics may include an MRI of the brain and orbits, but is not necessary for the diagnosis of optic neuritis [5]. MRI can help characterize the disease burden and assess the risk for the development of multiple sclerosis [7].
Given the patient’s age and constellation of symptoms, both neurology and ophthalmology consultation were performed with the leading concerning diagnosis being optic neuritis. The patient was admitted for further evaluation with a dilated ocular exam, MRs of the brain, and treatment.
Pathophysiology and Clinical Disease:
Optic neuritis is an inflammatory and demyelinating process that usually presents with monocular vision loss [3-4]. While there are many causes for optic neuritis, the demyelinating lesions seen in optic neuritis are similar to those that have been associated with multiple sclerosis. Patients are typically women between the ages of 20-40. Patients often develop progressive symptoms over a period of a few hours to several days.
Treatment and Timing:
Typical treatment is high dose intravenous steroids for three days. Another treatment regimen that has been described is intravenous methylprednisolone (250 mg four times per day) for three days, followed by oral prednisone (1 mg/kg per day) for 11 days, and then a four-day taper [8, 9].
If the diagnosis is uncertain, then is it acceptable to delay treatment for an MRI or specialist consultation the following morning?
The Optic Neuritis Treatment Trial described treatment of optic neuritis with high dose intravenous methylprednisolone. The initial multicenter trial enrolled 457 patients from July 1, 1988, through June 30, 1991. They ultimately randomized 389 patients with acute optic neuritis (and without known multiple sclerosis) to receive intravenous methylprednisolone (250 mg every six hours) for 3 days followed by oral prednisone (1 mg per kilogram of body weight) for 11 days, oral prednisone (1 mg per kilogram) alone for 14 days, or placebo for 14 days. They then assessed the neurologic status of the subjects for a period of two to four years and published their results in 1993. Also by following the subjects longitudinally, the authors were able to reanalyze the data and publish again in 2003. From the initial study, it was learned that high the steroids hastened the recovery of visual function, but did not affect long term visual outcomes when compared to both placebo and oral prednisone [10, 11, 12] after six months, and ten-year follow-up. It was found that a 3-day course of methylprednisolone reduced the rate of development of multiple sclerosis over a 2-year period [12]. Multiple sclerosis developed within the first two years in 7.5 percent of the IV methylprednisolone group vs. 14.7 percent of the oral prednisone group vs. 16.7 percent of the placebo group. The adjusted rate ratio for the development of definite multiple sclerosis within two years in the intravenous methylprednisolone group was 0.34 as compared with the placebo group and 0.38 as compared with the oral-prednisone group. However, after a 5-year period the treatment effect was no longer significant for the same group of patients.
Therefore, in a scenario when a provider may delay high dose steroids for a neurology and ophthalmology consultation, or for an MRI, it can be inferred that this delay will not affect long term outcomes for the patient. However, given that early treatment hastens symptom recovery and delays progression to multiple sclerosis, it may be beneficial to start high dose IV steroids in the emergency department in patients if optic neuritis is the suspected diagnosis.
Expert Commentary
This is a very good review of optic neuritis. There are just a few, additional nuanced points I’d like to mention, as well as some tips on counseling the patient.
Visual field changes: A central visual field deficit is commonly seen with this entity. It is most easily detected on formal visual field testing in the ophthalmology clinic (Humphrey or Goldmann visual fields), though some patients may report this on their own in the acute care setting.
Optic nerve swelling: In the ONTT, only 35% of patients had disc swelling (65% had normal appearing optic nerve heads on fundoscopy), so evaluating with ultrasound would not be revealing in most cases.
MRI for diagnosis: MRI is actually very important for the diagnosis of optic neuritis, as inflammation of a different part of the optic nerve (other than the nerve head) can only be visualized radiographically. MRI of the orbits and brain should be obtained with thin slices through the orbits, with fat suppression, and gadolinium (in addition to FLAIR sequences to look for demyelination).
Differential diagnosis: While this article talks about optic neuritis from demyelination related to possible MS, it’s important to bear in mind that there are other causes of optic neuritis: autoimmune disease (e.g., lupus), infections (e.g., syphilis or Lyme), other inflammatory conditions (e.g., sarcoidosis), other demyelinating processes (like neuromyelitis optica), or it can be idiopathic.
When counseling the patient about prognosis, it may be helpful to remember the “10-20-40-60” rule. I had been taught this, and it helps quickly summarize the ONTT prognostic statistics (that are outlined very nicely in this article). The “10-20-40-60 rule” mnemonic reminds us that at 10 years: there is a 20% chance of developing MS after an episode of idiopathic optic neuritis if there were no white matter lesions found on MRI; a 40% chance regardless of MRI findings; and, a 60% chance if 1+ white matter lesions are found on MRI.
It is also helpful to let the patient know that visual recovery is often excellent. Most patients return fairly close to their baseline vision within 3-5 weeks, although they may note some lingering difficulties with contrast sensitivity and color vision. An afferent pupillary defect may also persist.
Shira Simon, MD, MBA
Assistant Professor of Ophthalmology and Neurology
Northwestern Medicine
How to Cite This Post
[Peer-Reviewed, Web Publication] Chukwulebe S, Gappmaier V. (2019, March 11). Optic Neuritis. [NUEM Blog. Expert Commentary by Simon S]. Retrieved from http://www.nuemblog.com/blog/optic-neuritis
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Resources
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Vortmann M, Schneider JI. Acute monocular visual loss. Emerg Med Clin North Am. 2008;26(1):73-96, vi.
The clinical profile of optic neuritis. Experience of the Optic Neuritis Treatment Trial. Optic Neuritis Study Group. Arch Ophthalmol. 1991;109(12):1673-8.
UpToDate
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Beck RW, Arrington J, Murtagh FR, Cleary PA, Kaufman DI. Brain magnetic resonance imaging in acute optic neuritis. Experience of the Optic Neuritis Study Group. Arch Neurol. 1993;50(8):841-6.
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Sellebjerg F, Nielsen HS, Frederiksen JL, Olesen J. A randomized, controlled trial of oral high-dose methylprednisolone in acute optic neuritis. Neurology. 1999;52(7):1479-84.
Beck RW, Gal RL, Bhatti MT, et al. Visual function more than 10 years after optic neuritis: experience of the optic neuritis treatment trial. Am J Ophthalmol. 2004;137(1):77-83.
Beck RW, Trobe JD, Moke PS, et al. High- and low-risk profiles for the development of multiple sclerosis within 10 years after optic neuritis: experience of the optic neuritis treatment trial. Arch Ophthalmol. 2003;121(7):944-9.
Beck RW, Cleary PA, Trobe JD, et al. The effect of corticosteroids for acute optic neuritis on the subsequent development of multiple sclerosis. The Optic Neuritis Study Group. N Engl J Med. 1993;329(24):1764-9.