Population-Based Incidence of Acute Idiopathic Optic Neuritis Estimated

In patients with optic neuritis symptoms, over a third were eventually diagnosed with a different condition with the help of an MRI, while demyelinative lesions on the MRI were associated with higher risk of multiple sclerosis (MS), according to a study published in the Ophthalmic Epidemiology.

This population-based study sought to estimate the incidence of acute optic neuritis in Southern Finland between May 1, 2008, and April 14, 2012. The study further aimed to identify differential diagnoses of optic neuritis.

The study included 291 patients referred to the Helsinki University Hospital with symptoms suggestive of acute or subacute optic neuritis. Diagnosis of optic neuritis met common clinical criteria (some degree of color vision deficiency, combination of acute or subacute vision loss, eye pain, and possible afferent pupillary defect) and standard ophthalmoscopy techniques were used to confirm diagnosis.

MRI scans of the participants were performed within 24 hours of admission and allowed investigators to image the brain and optic nerve; participants were monitored for the development of MS during a mean follow-up time of 7.7 years.

Of the 291 participants, 184 (63%; 95% CI, 57% to 69%) received an optic neuritis diagnosis, while 107 (37%) were diagnosed with a different condition.

The most common differential diagnosis was non-arteritic anterior ischemic optic neuropathy, indicated in 12% of the participants. Of the participants diagnosed with optic neuritis, 76% were of were female and their ages ranged from 15 to 61, with a mean age of 34 years.

The incidence of optic neuritis in Southern Finland was 3.0 (95% CI, 2.8 to 3.3) per 100,000 people (4.6 females and 1.4 males).

Of the 184 patients diagnosed with optic neuritis, 123 (67%) were diagnosed as their first demyelinative episode, 2 (1%) were diagnosed with neuromyelitis optica, 56 (30%) were previously diagnosed with MS, and 3 (2%) had recurrent optic neuritis without an MS diagnosis.

In presenting with first episode of optic neuritis, MRI scans revealed demyelinating lesions in 82% (95% CI, 75% to 89%), a strong predictor of MS. In fact, 54% of patients first diagnosed with optic neuritis and demyelinating lesions were later diagnosed with MS during the follow-up period vs 5% without lesions.

Focusing on the population of Southern Finland limited the study by affecting generalizability to other ethnic groups with lower incidence of MS. Another study limitation did not account for people who did not necessarily seek medical treatment during an acute episode of optic neuritis.

Overall, the presence of demyelinating MRI lesions in patients with first optic neuritis predicted the development of MS. This study identified a subpopulation at significant risk and should facilitate physicians in the early diagnosis and treatment of MS.

Reference                                                                                                                       

Siuko M, Kivelä TT, Setälä K, Tienari PJ. Incidence and mimickers of acute idiopathic optic neuritis: Analysis of 291 consecutive patients from Southern Finland [published online July 24, 2018]. Ophthalmic Epidemiol. doi: 10.1080/09286586.2018.1500614