June 2018

COVER FEATURE

Neuro-ophthalmology for the anterior segment surgeon
Optic neuritis: When it is and when it isn’t


by Liz Hillman EyeWorld Senior Staff Writer


Severe optic disc swelling with heme, as shown in this picture, is highly atypical for optic neuritis and should raise concerns about an alternate diagnosis.
Source: Gregory Van Stavern, MD

Diagnostic pearls to follow and pitfalls to avoid to accurately diagnose this condition

Most comprehensive ophthalmologists have the skills and tools to effectively diagnose optic neuritis, said Gregory Van Stavern, MD, professor, Department of Ophthalmology, and director, Visual Electrophysiology Services, Washington University School of Medicine, St. Louis.
Yet, Dr. Van Stavern and co-investigators reviewed data of acute optic neuritis referrals and found nearly 60% from that set actually had an alternative diagnosis.1
“We were interested not only in the frequency of overdiagnosis but also what cognitive biases contributed,” Dr. Van Stavern said, sharing information from the study and other thoughts on behalf of the whole research team.
Ranya Habash, MD, assistant professor of ophthalmology, Bascom Palmer Eye Institute, Miami, a comprehensive ophthalmologist with a focus on cataract and refractive surgery, regularly staffs residents in the emergency room where optic neuritis cases may first present. Dr. Habash also discussed with EyeWorld what those without a neuro-ophthalmology subspecialty should know about the condition to improve diagnostic accuracy.

Overdiagnosis of optic neuritis

Stunkel et al. sought to assess not only the incidence of optic neuritis overdiagnosis but also the factors that contributing to it.1 In a retrospective, clinic-based, cross-sectional study, 122 new patients were referred for acute optic neuritis between January 2014 and October 2016. Of these, 49 (40.2%) had optic neuritis, while 73 (59.8%) had alternative diagnoses.
Why the high rate of initial misdiagnosis? Dr. Van Stavern said major factors were anchoring (or deciding upon a diagnosis early in the encounter and not adjusting one’s diagnosis with new or competing data based on the examination) and framing (or putting more weight on a clinical feature presented early in the encounter).
“Understanding the pitfalls leading to over diagnosis of optic neuritis may improve clinicians’ diagnostic process,” Stunkel et al. concluded in the study.

Diagnosing it right the first time

Optic neuritis is inflammation of the optic nerve. A wide variety of autoimmune and infectious diseases can cause optic neuritis, but the vast majority are cases of demyelinating optic neuritis, Dr. Van Stavern said, attributing much of what’s known about this condition to the Optic Neuritis Treatment Trial.2 The latter is often associated with multiple sclerosis and a few other demyelinating diseases and can be idiopathic/post-viral.
“For about 20% of multiple sclerosis patients, optic neuritis is their first manifestation of the disease, so it is important to diagnose it accurately to identify patients who are at risk for multiple sclerosis, and to avoid misclassifying patients who are not likely to develop multiple sclerosis,” Dr. Van Stavern said.
Typically, Dr. Habash said, patients will present with pain on eye movement and changes in vision. With that, she performs a thorough clinical exam, pupil exam, test for color vision and red desaturation (faded red vision), assessment for optic nerve swelling, and a basic neurologic exam. “If there is a high suspicion of optic neuritis,” Dr. Habash said, “an MRI is warranted, as it can help determine if the optic nerve is enhancing or if there are white matter lesions. At that point, I usually refer patients to a neuro- ophthalmologist for treatment.”
“It can be difficult to diagnose because many times, it’s just based on clinical history,” Dr. Habash said. “MRI can be a pivotal factor. If the clinical history is suggestive of optic neuritis, I would err on the side of obtaining the MRI because we don’t want to miss demyelinating disease.”
Dr. Van Stavern said the key features to look at are age range (usually 18–55 years old), pain upon movement of the eye, and subjective visual loss, often with scotoma. The clinical features include optic nerve dysfunction in the form of reduced visual acuity, impaired color vision, ipsilateral relative afferent pupillary defect, and optic nerve-related defect, such as central scotoma, arcuate or altitudinal field defect. Dr. Van Stavern noted that the optic disc is actually normal in about two-thirds of patients with optic neuritis and mildly swollen in about one-third. When there is swelling, he said that it’s mild and is rarely associated with hemorrhages.
“Color vision should be tested as this can often differentiate neurogenic from non-neurogenic visual loss,” Dr. Van Stavern explained. “Visual field testing should be performed to detect a visual field defect.”
Dr. Van Stavern said that every patient with demyelinating optic neuritis should have a brain MRI with and without gadolinium. This not only helps confirm optic neuritis but can stratify patients in terms of multiple sclerosis diagnosis or risk.
“The newest criteria for multiple sclerosis allow the diagnosis even after a single attack of optic neuritis, depending upon the MRI,” Dr. Van Stavern said.
“You need to be diligent about checking the pupils before dilation and making sure to check the color plates; these are ancillary tests that can lead you to the right diagnosis, even when an MRI is unavailable,” Dr. Habash said. “When we have a high clinical suspicion, we must rule out other major conditions like multiple sclerosis or immune disorders or infections that can cause optic neuritis.”

Avoiding misdiagnosis

“Over diagnosing this condition can be just as harmful as under diagnosis,” Dr. Van Stavern said. “Patients will go online and be terrified that they have multiple sclerosis. MRI scans can be misread, and we have seen patients misdiagnosed as having multiple sclerosis and being subjected to multiple sclerosis treatments.”
According the Stunkel et al. study, the most common alternative diagnoses in patients who did not have optic neuritis were headache, functional vision loss, and optic neuropathies, such as nonarteritic anterior ischemic optic neuropathy, traumatic optic neuropathy, and others of unclear etiology. Retinal conditions, such as central serous retinopathy, were also mistaken for optic neuritis, Dr. Van Stavern said.
Features that should raise concern for either atypical optic neuritis or another diagnosis are an age of more than 55 years, a lack of pain, the presence of macular edema, severe disc swelling with hemorrhages, or something in the history or review of systems such as malignancy or HIV.
“The lack of optic nerve dysfunction, and particularly the lack of a relative afferent pupillary defect, would argue strongly against optic neuritis,” Dr. Van Stavern said.
In terms of treatment and recovery, both Dr. Van Stavern and Dr. Habash said most patients will recover spontaneously back to or near baseline. Based on the Optic Neuritis Treatment Trial, Dr. Van Stavern usually recommends observation or treatment with high-dose IV methylprednisolone, which was shown to speed recovery, though it showed no difference in visual outcomes. A moderate dosage of oral prednisone (60 mg daily) did not, however, speed recovery and was associated with an increased risk for future optic neuritis episodes, Dr. Van Stavern noted.
If there is severe vision loss upon presentation with optic neuritis, Dr. Van Stavern said it can raise concerns about another demyelinating disorder, such as neuromyelitis optica. This can be diagnosed with a blood test.
As for the risk of recurrence of optic neuritis, Dr. Van Stavern said if the MRI shows at least one lesion associated with multiple sclerosis, the risk is 75% over 15 years; if the MRI looks normal, the risk of developing multiple sclerosis and/or having another optic neuritis episode is about 20% within 15 years.

References

1. Stunkel L, et al. Incidence and causes of overdiagnosis of optic neuritis. JAMA Ophthalmol. 2018;136:76–81.
2. Volpe NJ. The optic neuritis treatment trial: a definitive answer and profound impact with unexpected results. Arch Ophthalmol. 2008;126:996–9.

Editors’ note: Dr. Van Stavern and Dr. Habash have no financial interests related to their comments.

Contact information

Habash: ranya@hipaachat.com
Van Stavern: vanstaverng@wustl.edu

Optic neuritis: When it is and when it isn’t Optic neuritis: When it is and when it isn’t
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