Amalric Triangular Syndrome Associated With Outer Nuclear Layer Infarction

Introduction

Amalric first described the “triangular syndrome” as a wedge-shaped area of early choroidal hypofluorescence with late staining caused by choroidal ischemia.¹ There have been many subsequent reports describing a variety of conditions with this triangular sign, especially giant cell arteritis (GCA).^2,3

The outer nuclear layer (ONL) comprises photoreceptor axons and, along with the photoreceptor inner and outer segments, receives its blood supply predominantly from the underlying choriocapillaris. There are various conditions that can cause ONL disruption, including placoid disorders,⁴ laser injury,⁵ and acute macular neuroretinopathy (AMN).^6,7

Here, we present a patient with GCA complicated by choroidal ischemia and associated with adjacent ONL abnormalities with spectral-domain optical coherence tomography (SD-OCT).

Case Report

An 85-year-old male with history of atrial fibrillation and pacemaker placement presented with temporal headache of 1-hour duration and a 1-week history of vision loss in the left eye. More recent vision loss was noted in the right eye. Visual acuity was 20/30 with paracentral scotoma in each eye. Anterior segment exam was within normal limits. Funduscopic examination was unremarkable in the right eye but demonstrated triangular zones of peripheral retinal whitening temporal to the macula in the left eye (Figures 1A and 1B). Fluorescein angiography (FA) was unremarkable in the right eye, whereas the left eye illustrated zones of hypofluorescence (Figure 1C) with late staining in a triangular distribution extending from the temporal macula to the periphery. SD-OCT illustrated multifocal paracentral hyperreflective lesions of the ONL associated with disruption of the ellipsoid and interdigitation zones and adjacent to a temporal area of choroidal hyperreflectivity corresponding to the choroidal infarct (Figure 1G). A questionable small paracentral acute middle maculopathy lesion was noted temporally in the right eye (Figure 1E). Emergent erythrocyte sedimentation rate (82 mm/hr) and C-reactive protein levels (26.4 mg/L) were obtained and were remarkably abnormal. The patient was treated with high-dose intravenous steroids, and the result of temporal artery biopsy performed the next day was consistent with the diagnosis of GCA. Following treatment, the patient's systemic and visual symptoms significantly improved.

Figure 1. Color fundus photography of right (A) and left (B) eyes at baseline presentation. The left eye demonstrates triangular zones of peripheral retinal whitening in the temporal macula (outlined by arrows). Fluorescein angiography of the left eye (C) demonstrates early triangular hypofluorescent nonperfusion of the choroid (outlined by arrows). Near-infrared reflectance (NIR) and spectral-domain optical coherence tomography (SD-OCT) of the right eye (D, E) illustrate a possible small paracentral acute middle maculopathy lesion temporal to the fovea (outlined by arrows). NIR and SD-OCT imaging of the left eye (F, G) illustrate hyperreflective lesions of the outer nuclear layer associated with disruption of the ellipsoid and interdigitation zones (outlined by arrows) adjacent to the area of choroidal infarct that demonstrates abnormal hyperreflectivity.

At 2-week follow-up, visual acuity was 20/30 in both eyes with resolution of the scotoma of the right eye and partial improvement of the scotoma of the left eye. Retinal examination was notable for triangular pigmentary changes in the temporal macula of the left eye with staining on FA (Figures 2A and 2B). SD-OCT of the right eye was unremarkable, whereas the left eye demonstrated thinning of the ONL and persistent disruption of the ellipsoid and interdigitation zones (Figures 2C–2F).

Figure 2. Color fundus photography of left eye (A) at 2-week follow-up demonstrates triangular pigmentary changes in the temporal macula (outlined by arrows), whereas fluorescein angiography (B) illustrates staining of the corresponding area. Near-infrared reflectance (NIR) and spectral-domain optical coherence tomography (SD-OCT) of the left eye (C, D) demonstrate thinning of the outer nuclear layer and persistent disruption of the ellipsoid and interdigitation zones (outlined by arrows). NIR and SD-OCT of the right eye at 2-week follow-up are unremarkable (E, F).

Discussion

The triangular sign of Amalric is a wedge-shaped or triangular zone of choroidal infarction due to posterior ciliary occlusion or hypoperfusion.¹ The choroidal circulation originates from the medial and lateral posterior ciliary arteries, which branch into short and long posterior ciliary arteries. The short posterior ciliary arteries pierce the sclera around the optic nerve and supply the posterior pole. The long posterior ciliary arteries course along the horizontal midline and supply a triangular zone of the choroid with the apex at the posterior pole and the wide base extending to the periphery. These triangular areas comprise adjacent watershed regions that are prone to ischemia,⁸ as was illustrated in this case due to GCA.

Choroidal ischemia is a well-described complication of GCA, a systemic vasculitis of large and medium-sized arteries of the head and neck.⁹ GCA is considered to be a true ophthalmologic emergency, since it can cause permanent vision loss due to ischemia of the optic nerve, retina, choroid, and intracranial structures. GCA has a predilection for ischemic lesions of the posterior ciliary arteries that are the main vascular supply of the choroid, the anterior optic nerve and the cilioretinal artery and a delay in diagnosis and therapy can lead to irreversible blindness.³

This report of a classic Amalric sign of choroidal ischemia associated with adjacent OCT findings of ONL infarction is a novel finding. The majority of blood supply to the photoreceptors originates from the choriocapillaris. The association of choroidal ischemia with outer retinal abnormalities may occur in various disorders including the placoid spectrum of diseases,⁴ but this patient failed to demonstrate any evidence of acute posterior multifocal placoid pigment epitheliopathy with color fundus photography or fluorescein angiography. Although the OCT findings were similar to an AMN-like presentation, the near-infrared image failed to demonstrate hyporeflectivity typical of AMN. Moreover, the pathogenesis of AMN is in debate. Whereas Fawzi et al. have suggested deep retinal capillary plexus ischemia as the etiology,⁷ recent studies using OCT angiography have proposed inner choroidal ischemia.¹⁰ Further investigation is required to determine if AMN is the result of ischemia and if the principle level of injury resides in the deep retinal capillary plexus or the choroid.