Implications of a Swollen Optic Nerve

The study by Crum et al¹ presents a retrospective review of 86 patients who presented to an eye clinic during 24 years and were found to have papilledema (optic nerve head swelling secondary to elevated intracranial pressure). Most patients (58 patients [67%]) were found to have idiopathic intracranial hypertension (IIH). The next most common etiology of the papilledema was previous trauma or a known intracranial mass (19 patients [22%]), and the final group (9 patients [10%]) had a newly discovered intracranial process (tumor, hemorrhage, meningitis, or venous sinus thrombosis). Consistent with the IIH Treatment Trial results, patients with IIH in this study were most commonly women, presented with a headache, and had a higher body mass index.² These findings may help to guide eye care providers in triaging patients presenting to the clinic with papilledema and identifying more unusual or concerning characteristics that may warrant a more extensive workup.

This article is quite timely, given that distinguishing the various causes of disc edema and elevation can be quite difficult—especially for the non–eye care professional—and multiple imaging technologies have emerged to facilitate accurate identification of optic nerve head swelling (fundus photography, optical coherence tomography [OCT], OCT-angiography, fundus autofluorescence, ultrasonography). These ubiquitous tools are now present in many ophthalmologic and optometric practices and even some emergency departments, resulting in many more urgent referrals for a concern of papilledema. It is reassuring to see in this article,¹ as we have seen with previous studies surveying patients presenting to the emergency department with headaches and other symptoms, that most true cases of papilledema will ultimately be of benign etiology.³

Nevertheless, there remain many nuances to the proper diagnostic process—particularly in the distinction of pseudopapilledema and other causes of disc edema from papilledema—that are critical to appropriate evaluations and neuroimaging and treatment plans. While an OCT algorithm may demonstrate a thickened retinal nerve fiber layer suggestive of disc edema, this is not necessarily papilledema. To further complicate clinical decision-making, other entities, such as intrinsic disc edema without elevated intracranial pressure (as occurs with ischemic optic neuropathy or optic neuritis) or pseudopapilledema (eg, optic disc drusen or anomalous crowded optic nerve heads), may be present. In the latter scenario of pseudopapilledema, especially in patients without systemic symptoms, there is a low prevalence of structural causes coinciding with this disc appearance, and deferring of urgent imaging can be permissible. As the study by Crum et al¹ points out, there are also non-IIH causes of papilledema. The study included patients with several of these (including tumor, hemorrhage, meningitis, and venous sinus thrombosis); other etiologies could include hydrocephalus (as with congenital aquaductal stenosis) and spinal cord lesions (eg, ependymomas or neurofibromas).⁴

The IIH Treatment Trial helped us understand characteristics of a typical patient with IIH: female, with obesity, and experiencing constant or daily headaches, transient visual obscurations, and/or pulse synchronous tinnitus.¹ The Modified Dandy criteria helped to provide clinical and radiographic guidelines to diagnose IIH (signs or symptoms of IIH; no neurologic defects aside from a sixth nerve palsy; normal neuroimaging results aside from findings known to be associated with elevated intracranial pressure, such as an empty sella, globe flattening, and transverse venous sinus stenosis; increased cerebral spinal fluid opening pressure on lumbar puncture [generally >25 cm H₂O with normal cerebrospinal fluid constituents]; and no other cause of the elevated intracranial pressure).^5,6 When patient demographic characteristics and clinical and radiographic findings do not precisely match these guidelines, the differential remains quite broad. And even when they mostly do—for instance in the small subset of patients who have true papilledema and are women with obesity without localizing neurologic signs—they may still be harboring life-threatening non-IIH intracranial pathologies, such as tumors and venous sinus thromboses.

We see evidence of exactly this in the population of the study by Crum et al¹: the 2 patients (3%) who had structurally important causes of elevated intracranial pressure were difficult to distinguish from those patients with IIH. Similarly, three-quarters of those patients examined in the non-IIH group had no focalizing neurologic signs, and headaches can be prevalent in both IIH and non-IIH populations; this can make the distinction exceedingly difficult to make in a clinical setting. It is also worthwhile to note that the study by Crum et al¹ examined a narrower subset of patients—those presenting to the eye clinic, presumably with a paucity of neurologic symptoms and signs compared with other cohorts, such as those presenting to emergency departments or neurology clinics and other care settings with papilledema and associated systemic symptoms. Previous studies, such as that by Biousse et al,⁷ have articulated precisely this difficulty in differentiating IIH from non-IIH patients. Ultimately, urgent magnetic resonance imaging and magnetic resonance venography become integral to ensuring those life-threatening cases and critical moments to intervene are not missed.

Disc edema of any form is a concerning finding. A thorough ophthalmologic examination and often neuro-ophthalmologic consultation are important in distinguishing normal variants from acute, urgent pathology.

Published: June 2, 2020. doi:10.1001/jamanetworkopen.2020.7159

Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2020 Simon S et al. JAMA Network Open.

Corresponding author: Shira Simon, MD MBA, Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, 645 North Michigan Avenue Suite #440, Chicago, IL 60611 (shira.simon@nm.org).

Conflict of Interest Disclosures: None reported.