Dural Spot Sign in Central Retinal Artery Occlusion

Introduction

Central retinal artery occlusion (CRAO) causes an abrupt cessation of blood flow to the inner retinal layers with progressive retinal ganglion cell ischemia leading to debilitating visual impairment. Similar to ischemic stroke, proximal embolism is considered a main cause of CRAO. Transorbital sonography (TOS, suppl. Fig. 1) is particularly useful for the identification of embolic CRAO, as it allows visualization of hyperechogenic embolic material within the central retinal artery (CRA). The “retrobulbar spot sign” (RBSS) indicates vessel occlusion, most likely caused by a fresh cholesterol or calcified embolus at the lamina cribrosa, proximal to the division of the retinal arterioles ([Fig. 1]). Interestingly, anatomical studies locate the narrowest section of the CRA at the point where it pierces the dura mater to enter the optic nerve sheath, located at a variable distance of 10 mm from the eyeball (S. Hayreh et al. Br J Ophthalmol 1960; 44(4): 193–212). However, to the best of our knowledge, no studies have described visible CRA emboli at the level of optic nerve sheath entry. Here, we present three cases of CRAO with the “dural spot sign” visible on TOS.

Fig. 1 Origin and anatomical course of the central retinal artery (CRA). After the CRA emerges from the ophthalmic artery, two distinct anatomical points of narrowing can be identified within the course of the vessel: The first narrowing occurs where the CRA passes through the dural sheath and enters the optic nerve. Another constriction occurs as the CRA passes through the lamina cribrosa shortly before dividing into the terminal retinal branches. CRA: central retinal artery. Created with BioRender.com. [rerif]

Publication History

Received: 08 April 2024

Accepted after revision: 19 April 2024

Accepted Manuscript online:
19 April 2024

Article published online:
22 May 2024