Errors Abound in Diagnosing Optic Neuritis--How Can We Fix Them?

Brianne N. Hobbs, OD


January 03, 2019

Thinking about mistakes, especially medical mistakes, is uncomfortable. It is certainly more enjoyable to read about a promising new therapy than to scrutinize the reasons that medical mistakes are happening. Yet, medical mistakes are currently the third leading cause of death in the United States, and despite their prevalence, there is no systematic way of reporting such errors.[1]

Death is not the only adverse outcome of medical errors, and it is estimated that mistakes causing serious harm are 10-20 times more common than those causing lethal harm.[2] Misdiagnosis is one category of medical mistakes that may result in unnecessary referrals, procedures, and treatments. A seemingly simple way to deliver better care is to identify common mistakes and correct them. This process isn't glamorous, but it is productive.

Focus on Optic Neuritis

In a recent study,[3] one large university-based neuro-ophthalmology clinic addressed the problem of misdiagnosis of optic neuritis. Over a 2-year period, the clinic received 122 referrals for optic neuritis. The records for each of these patients were examined retrospectively to determine whether the diagnosis of optic neuritis was accurate and, if not, the reasons that commonly led to misdiagnosis.

Alarmingly, 73 of the 122 patients referred to this center with a diagnosis of optic neuritis were actually misdiagnosed. This misdiagnosis rate of approximately 60% was consistent among all referral sources, including optometrists, ophthalmologists, and neurologists. The most common alternative diagnoses were headache with concurrent eye pain (22%), functional vision loss (19%), and other optic neuropathies (16%), including nonarteritic ischemic optic neuropathy (NAION; 12%). Patients older than 50 years were more likely to be misdiagnosed with optic neuritis.

The Path to Misdiagnosis

Why were so many patients misdiagnosed as having optic neuritis? The most common error was failure to interpret the critical elements of the history, which occurred in 33% of the patients. Specifically, an overreliance on a previous diagnosis of multiple sclerosis or optic neuritis led to inaccuracy in diagnosis. Additionally, too much emphasis was often given to eye pain or pain with eye movement, which was found in the referral notes of 29% of patients ultimately diagnosed with a different condition. Another source of diagnostic error was ignoring normal exam findings; the possibility of optic neuritis can almost be excluded entirely if the complete ocular examination is normal. Red cap desaturation testing was often given too much emphasis, resulting in the diagnosis of optic neuritis solely on one abnormal, subjective test.

Although the misdiagnosis of optic neuritis is not a lethal mistake, multiple patients received expensive and invasive procedures, such as MRI and lumbar punctures, which were not indicated. Eight patients were treated unnecessarily with IV steroids. Four patients diagnosed with optic neuritis actually had neoplasms. The cost of misdiagnosis was not death, but it did result in patient harm.

There are five major clinical applications of this study:

  1. Optic neuritis almost always results in an abnormal MRI due to T2 hyperintensity or enhancement of the optic nerve; a normal MRI argues strongly against optic neuritis.

  2. The presence of an afferent pupillary defect was strongly correlated with a true diagnosis of optic neuritis; only 21% of patients who had been documented as previously having normal pupillary testing were ultimately diagnosed with optic neuritis.

  3. Pain upon eye movement is often caused by a headache with associated eye pain or visual disturbances and is not pathognomonic for optic neuritis.

  4. NAION is often misdiagnosed as optic neuritis in elderly patients, even though NAION has a higher incidence in this demographic.

  5. No single element of the case history should determine the diagnosis, as this leads to diagnosis bias and a failure to consider other possible diagnoses.

Atul Gawande, in his book Complications: A Surgeon's Notes on an Imperfect Science,[4] writes that "not only do all human beings err, but they err frequently and in predictable patterned ways." Gathering data about these "predictable patterned ways" that clinicians err would help describe the scope of the problem, identify specific cognitive biases that lead to misdiagnosis, and generate explicit recommendations to improve patient care.

While this study was small and limited in scope, the methodology has broad applicability in enhancing patient care by reducing medical mistakes.

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