Appearance and resolution of numerous bilateral gass plaques in probable Susac syndrome

Abstract

Purpose: To describe a patient with a unique retinal phenotype of probable Susac syndrome.

Observations: A 47-year-old female who presented with bilateral tinnitus and vision changes was found to have bilateral sensorineural hearing loss and many bilateral retinal arteriolar Gass plaques. She had bilateral scotomas corresponding with temporal thinning and atrophy of the inner nuclear layer (INL) on OCT. Retinal examination and fluorescein angiography demonstrated minimal arteriolar wall hyperfluorescence with no evidence of acute branch retinal artery occlusion. She developed daily headaches. MRI of the brain was normal with no corpus callosal lesions. She was diagnosed with probable Susac syndrome based on the above findings.

Conclusions and importance: Our patient's bilateral high frequency sensorineural hearing loss, numerous bilateral Gass plaques, and headaches are most likely attributable to Susac syndrome. While BRAO is considered a cornerstone of retinal involvement in Susac syndrome, it may only be appreciable angiographically in the acute setting, and it is important to recognize Gass plaques as a significant diagnostic marker of disease.

Keywords: Arteriolar wall hyperfluorescence; Branch retinal artery occlusion; Gass plaque; Susac syndrome.

Fig. 1

Visual Fields. Humphrey visual fields using a 30-2 static perimetry demonstrating nasal paracentral scotomas in both eyes, more prominent in the left.

Fig. 2

Fundus Photos. Color fundus photographs of the left (A) and right (B) eyes demonstrating numerous and diffuse Gass plaques (arrows) in all quadrants. The optic nerve heads and maculae are healthy in appearance and there is no funduscopic evidence of BRAO in either eye. The right eye shows two small cotton wool spots adjacent to a small flame hemorrhage nasal to the disc (asterisk). Panel (C) shows a magnified view of the superior periphery of the right eye demonstrating many Gass plaques along an arteriolar segment (arrow). Note that these plaques are yellow, nonrefractile and are along straight segments of vasculature, not at retinal arteriolar bifurcations. Also shown here are two areas that clinically resemble arteriolar sheathing (asterisks).

Fig. 3

Fluorescein Angiography. Two areas of arteriolar wall hyperfluorescence (arrows) in the temporal periphery (A) and inferonasal periphery (B) of the right eye. The vessel in the temporal periphery appeared normal on funduscopic exam while the vessel in the inferonasal periphery did appear sheathed clinically. Mild vessel wall hyperfluorescence can be seen in the far temporal periphery in normal eyes, so panel (A) may or may not indicate pathologic AWH due to SS. (C) There were no such areas of AWH seen on FA of the left eye. Note that there was no evidence of acute arteriolar occlusion in either eye.

Fig. 4

Elongated Gass Plaque. Magnified view of a superior peripheral arterial branch of the right eye which clinically resembled vascular sheathing (A), however did not stain on FA (B) and over several months of follow-up dissolved into more discrete appearing Gass plaques (C) and ultimately resolved completely. (D) Therefore, this area was likely an elongated Gass plaque representing an extended area of lipid extravasation. Gass plaques are invisible on FA.

Fig. 5

OCT Macula of the right (A) and left (B) eyes which demonstrate normal central architecture and no evidence of acute arterial obstruction, but show bilateral temporal inner retinal thinning and atrophy of INL (arrows) consistent with past occlusive events.