By Marc Dinkin, MD

Director of Neuro-Ophthalmology; Associate Professor, Departments of Ophthalmology and Neurology, Weill Cornell Medical College

Dr. Dinkin reports he is a consultant for Serenity Medical, Inc.

SYNOPSIS: In a population-based study in Olmstead County, MN, during the period 1990 to 2014, the incidence of papilledema was 2.5/100,000 persons per year, and most patients were diagnosed with idiopathic intracranial hypertension.

SOURCE: Sachdeva V, Vasseneix C, Hage R, et al. Optic nerve head edema among patients presenting to the emergency department. Neurology 2018;90:e373-e379.

Assessment of optic nerve appearance in patients with headache and other neurological symptoms is essential to rule out papilledema, a sign of elevated intracranial pressure that could reflect serious, life-threatening disease. Its prevalence within certain patient populations has been assessed previously, but estimating its prevalence within a population has been challenging. To better assess the prevalence of papilledema within a population, as well as the distribution of underlying etiologies, Crum and colleagues performed a retrospective, cross-sectional incidence study in Olmstead County, MN. Using the Rochester Epidemiology Project database, which has collected data from nearly all medical systems in the county since 1966, the authors searched for all cases of newly diagnosed papilledema seen in outpatient eye clinics in patients who resided in the county between 1990 and 2014.

Using these criteria, the authors identified 86 patients, 19 (22%) of whom had previously identified causes of intracranial hypertension. Among the remaining 67 patients, nine (10%) were found to have a secondary cause, while the remaining 58 (67%) were diagnosed with idiopathic intracranial hypertension (IIH), a disease that mostly affects obese woman of childbearing age, in whom there is no clear identifying cause of intracranial hypertension. Not surprisingly, those with IIH were more likely to be female (91% vs. 54%) and have an elevated body mass index (BMI) (37.5% vs. 26.9%), but less likely to have localizing signs other than an abducens palsy (0% vs. 7%). Interestingly, the IIH patients were more likely to present with a headache (93% vs. 68%).

Secondary causes among those who were not previously diagnosed included venous sinus thrombosis (4), tumor (4), and granulomatous meningitis (1). The low rate of localizing signs in this group (occurring in two, both from tumors) likely played a role in the fact that they had not been diagnosed previously with their underlying condition. Not surprisingly, the non-IIH patients were more likely to have localizing neurological deficits, which occurred in two (22%) of the patients secondary to tumor, and had a lower median BMI than IIH patients. More surprising, though, was the finding that headaches were much more common in the IIH group (93%) than in the non-IIH patients (67%). Since opening pressures were not analyzed, we do not know if this difference results from higher intracranial pressure (ICP) in the IIH group, or from some other factor.

COMMENTARY

One of the strengths of this study was its use of the Rochester Epidemiology Project database. It allowed the authors to estimate the incidence of papilledema, 2.5/100,000 per year, in their population. Their finding that 87% of patients whose papilledema did not already have a known cause ended up being diagnosed with IIH is noteworthy but might lull neurologists into a sense that most papilledema they see will not reflect an underlying structural lesion. However, the results of this study should be interpreted with great caution by neurologists, since the subjects were limited to those evaluated in an outpatient ophthalmology or optometry clinic. Had the population instead been those found to have papilledema in the emergency room, or even in the neurology clinic (where additional neurologic symptoms and signs would be more likely), then the relative incidence of underlying disease states other than IIH likely would have been higher, as it has been in prior studies. Additionally, search terms used in this study included “IIH” and “papilledema,” but did not include “brain tumor,” “venous sinus thrombosis,” or “meningitis.” Therefore, any patients with those conditions who had papilledema that was either not noticed or not coded for would not have been included. Neurologists also must keep in mind etiologies of disc edema other than high ICP, such as anterior ischemic optic neuropathy and optic neuritis, which sometimes may present bilaterally and mimic papilledema, but were excluded from this study.

This ambitious study shines a light on the incidence and characteristics of papilledema in a geographic population over the course of a quarter of a century. Neurologists should bear its conclusions in mind, and also keep in mind the differences between patients who present to eye clinics and those who present to neurologists.