Pediatric Optic Nerve Drusen

10 year old with right eye pain • Xray of the Week

Name the condition and clinical significance.

Figure 1. Axial CT scan of the orbits.

Figure 2. Axial CT scan of the orbits. A: Punctate calcification at the right optic nerve head junction (red arrow) and normal left optic nerve head junction (green arrow).B: Magnified view of the right orbit showing punctate calcification at the right optic nerve head junction (red arrow).

Discussion:

Introduction:

Optic nerve drusen are abnormal collections of mucoprotein matrix, acid mucopolysccharides, and ribonucleic acids that accumulate within the optic nerve, on the surface of the optic disc, and in the peripapillary retina [1]. Drusen are initially “buried” within these locations but become more visible as they calcify and nerve fibers atrophy [1]. They occur in 0.4% of children and become visible at 12 years of age, on average [1]. A correct diagnosis of optic nerve drusen is important because this condition can be easily misdiagnosed as papilledema, which leads to unnecessary imaging and procedures such as lumbar punctures [1].

Pathogenesis:

There are three theories on the formation of optic nerve drusen. One theory is that a disturbance in axonal metabolism results in reduced axoplasmic flow [1]. Another theory is that congenitally dysplastic discs have a predisposition towards drusen formation [1]. Finally, it is possible that a small scleral canal compresses the optic nerve, leading to ganglion cell death with calcification of mitochondria [1].

Presentation:

Although the majority of optic nerve drusen are asymptomatic, children with symptomatic optic nerve drusen can present with headache, vomiting, or seizures [1]. Optic nerve drusen can also cause visual field defects, especially if they are superficial rather than buried. Visual field constriction is also seen in 50% of eyes with superficial drusen, but only 17% of eyes with buried drusen [1]. The most common visual field defect is a nasal inferior arcuate scotoma, making up about a third of all visual field defects associated with optic nerve drusen [1]. On ophthalmologic exam, patients can have an afferent pupillary defect if the optic nerve drusen are asymmetric or unilateral [2].

Complications:

If left untreated, optic nerve drusen can lead to a variety of complications, the most important of which is blindness. Optic nerve drusen can rarely lead to retinal vascular abnormalities that lead to anterior ischemic optic neuropathy and eventual vision loss [4].

Figure 3. CT scan of the orbits. A: Sagittal oblique view of the right orbit showing the punctate calcification at the optic nerve head junction (red arrow). B: Sagittal oblique view of the left orbit showing the normal optic nerve head junction (green arrow).

Diagnosis:

Superficial optic nerve drusen can be seen on fundoscopic exam as an elevated, nodular optic disc with blurred margins [3]. The drusen appear as multiple whitish-yellow granules and are often bilateral [2]. Buried optic nerve drusen are more difficult to appreciate but can be seen adjacent to vessels or the optic disc margin. Besides a fundoscopic exam, imaging modalities such as ultrasound, CT scan, or fluorescein angiography can assist in diagnosing optic nerve drusen.

Figure 4. Ultrasound of the right globe in a different patient, a 57 year old female with right orbital pain. An optic nerve drusen is seen as a hyperechoic nodule (yellow arrow) with posterior acoustic shadowing (blue arrow).

Ultrasonography is superior to other methods for detecting superficial drusen and can identify around 50% of buried drusen due its sensitivity to calcium deposits buried deeply in the optic tissue [2,4]. On ultrasound, the drusen generally appear hyperechoic with posterior shadowing [2] (Fig. 4). They are commonly located on the nasal side of the optic disc [2].

Although CT scan can miss smaller drusen, it is still capable of detecting calcified optic nerve drusen [1]. In this example, a right optic nerve drusen was discovered on CT scan of the orbits as seen in Figures 1-3.

Treatment:

Currently, there are no effective treatments for optic nerve drusen. If the patient is asymptomatic, they can be observed with serial visual field testing [3]. If visual field defects occur and start to progress, patients can be treated with topical ocular hypotensive therapy. Surgical treatment options include optic nerve sheath fenestration or radial optic neurotomy. Neither are considered the standard of care, but there have been reports of successful treatment [3]. ​​​​

References:

1. Chang MY, Pineles SL. Optic disk drusen in children. Surv Ophthalmol. 2016;61(6):745-758. doi:10.1016/j.survophthal.2016.03.007

2. Tuğcu B, Özdemir H. Imaging Methods in the Diagnosis of Optic Disc Drusen. Turk J Ophthalmol. 2016;46(5):232-236. doi:10.4274/tjo.66564

3. Allegrini D, Pagano L, Ferrara M, et al. Optic disc drusen: a systematic review : Up-to-date and future perspective. Int Ophthalmol. 2020;40(8):2119-2127. doi:10.1007/s10792-020-01365-w

4. Kumaev B, Soule E, Rao D, Fiester P. Optic Disc Drusen. Appl Radiol. 2020;49(6):54-55. https://www.appliedradiology.com/communities/CT-Imaging/optic-disc-drusen

Leslie Shang is a 6th-year medical student at the University of Missouri – Kansas City Six-Year BA/MD Program and an aspiring radiologist. At UMKC, she serves as the social media coordinator of the Radiology Interest Group. She is also the vice president of the Help a Life Organization (HALO) which serves free meals to patients at the student-run free clinic and provides educational lectures to students on healthy eating and diet counseling for patients. In her free time, she enjoys exploring new restaurants in Kansas City, hiking, and spending time with friends.

Follow Leslie on Twitter @LeslieFShang

All posts by Leslie Shang

Kevin M. Rice, MD is the president of Global Radiology CME

Dr. Rice is a radiologist with Renaissance Imaging Medical Associates.He has held many leadership positions including Chair of Radiology, Chief of Staff and Hospital Board member at Valley Presbyterian Hospital in Los Angeles, California. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015, Dr. Rice and Natalie Rice founded Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" Award for the Most Effective Radiology Educator.

Follow Dr. Rice on Twitter @KevinRiceMD

All posts by Kevin M. Rice, MD