Retrobulbar Spot Sign in Metachronous Bilateral Central Retinal Artery Occlusion of Cardioembolic Origin

Abstract

A 78-year-old man suffered sudden visual loss of his right eye. Five years earlier, he had experienced vision loss of his left eye due to central retinal artery occlusion (CRAO); back then, the etiology for the CRAO was not established. Current ocular ultrasound depicted a hyperechoic spot within the optic nerve in both eyes. Echocardiography identified a calcified mass adherent to the mitral valve as the embolic source of the CRAO. This case shows the value of ocular B-mode ultrasound in demonstration and proof of the etiology for CRAO.

A 78-year-old male patient was admitted to the emergency room of the Department of Ophthalmology with sudden onset of severe, painless visual loss (only perception of hand movements) of his right eye. Five years earlier, the patient already lost vision of his left eye due to central retinal artery occlusion (CRAO). At that time, a limited diagnostic workup (without cardiac examination) was performed, but a definite etiology was not established.

Funduscopic examination revealed an acute CRAO of the right eye with retinal edema, narrowed arterial vessels, and a cherry-red spot of the macula. The left eye showed disc pallor and retinal atrophy. Headache, jaw claudication, or symptoms of polymyalgia rheumatica were denied. The patient's cardiovascular risk profile included diabetes mellitus and arterial hypertension. There was no history of heart disease, atrial fibrillation, or rheumatic fever. He was normal weight (body mass index 20.6), afebrile, and normotensive (115/65 mm Hg). Physical examination revealed a regular heart action, no murmurs, and no arterial bruits over the carotid or axillary arteries. Complete blood count and acute phase reactants were within the normal range. Duplex sonography did not reveal significant carotid artery stenosis, and there were no sonographic signs of cranial giant cell arteritis. However, ocular B-mode ultrasound, performed with a 9-MHz linear probe, depicted a hyperechoic spot within the optic nerve close to the optic nerve head in both eyes (Fig. 1; See Supplemental Digital Content 1, Video 1, https://links.lww.com/WNO/A395). Transthoracic and transesophageal echocardiography identified a large hyperechoic floating mass adherent to the posterior leaflet of the mitral valve as possible embolic source (See Supplemental Digital Content 2, Video 2, https://links.lww.com/WNO/A396). Only mild mitral valve insufficiency was present, and left ventricular function was normal. There was no evidence of atrial fibrillation episodes in 24-hour Holter electrocardiogram.

FIG. 1.: Ocular B-mode ultrasound of both eyes showing the echogenic spot (arrow) in the optic nerve head of the right and left eyes.

As there were no symptoms or signs of systemic inflammation and repeating blood cultures were negative, active endocarditis was deemed to be unlikely. Anticoagulant treatment with rivaroxaban 20 mg once daily was initiated. Follow-up transesophageal echocardiography 4 weeks after initiation of anticoagulation documented a significant size reduction of the mass, in line with the assumption of a calcified thrombus based on degenerative mitral valve pathology. Best-corrected vision remained highly impaired (only perception of hand movements with both eyes).

CRAO most often has an embolic cause, either originating from large artery arteriosclerosis, for example, carotid artery stenosis, or from a cardiac source. In rare cases, CRAO occurs secondary to giant cell arteritis. These cases are typically accompanied by cranial and systemic symptoms of the disease, such as headache, jaw claudication, and scalp tenderness. In some patients with embolic CRAO, a retrobulbar echogenic structure of the optic nerve can be detected by ultrasound (¹). The so-called retrobulbar spot sign has a high negative predictive value for vasculitic CRAO but is frequently found in embolic CRAO (²). Moreover, it has been suggested that a positive retrobulbar spot sign predicts unfavorable outcome of systemic thrombolysis in acute CRAO (³). In a small case series, the retrobulbar spot sign persisted in all patients after a median follow-up of 17 months and was associated with low rates of spontaneous recanalization and visual improvement (⁴).

In our case, the retrobulbar spot sign confirmed the embolic nature of bilateral, metachronous CRAO even 5 years after the index event. Ocular B-mode ultrasound can easily be performed and has important diagnostic and prognostic implications in CRAO.

STATEMENT OF AUTHORSHIP

Category 1: a. Conception and design: C. Lottspeich, M. J. Mackert, and M. Czihal; b. Acquisition of data: C. Lottspeich, M. J. Mackert, A. Köhler, and M. Czihal; c. Analysis and interpretation of data: C. Lottspeich, M. J. Mackert, A. Köhler, A. Bauer, U. Hoffmann, and M. Czihal. Category 2: a. Drafting the manuscript: C. Lottspeich, M. J. Mackert, A. Köhler, A. Bauer, U. Hoffmann, and M. Czihal; b. Revising it for intellectual content: C. Lottspeich, M. J. Mackert, A. Köhler, A. Bauer, U. Hoffmann, and M. Czihal. Category 3: a. Final approval of the completed manuscript: C. Lottspeich, M. J. Mackert, A. Köhler, A. Bauer, U. Hoffmann, and M. Czihal.