Reuben Oza
Introduction
Susac syndrome, characterised by branch retinal artery occlusion, encephalopathy and sensorineural hearing loss, is a rare autoimmune condition which was first described by John Susac in 1979 (1). This article aims to provide an insight into the pathophysiology, clinical features, diagnosis and management of Susac syndrome.
Pathophysiology
In Susac syndrome, autoimmune endotheliopathy occurs, in which endothelial cells of the small arterioles of the retina, inner ear and brain are damaged. Autoimmune processes resulting in this microangiopathy include deposition of microinfarcts within the small arterioles, vasogenic occlusion and anti-endothelial cell antibodies causing endothelial cell necrosis (2).
Clinical Features
Susac syndrome is more commonly found in females, especially those of Caucasian background (2). Presentation is explained by the affected locations in Susac syndrome, which include the brain, eye and inner ear, however it is important to note that patients do not typically present with the complete triad of encephalopathy, sensorineural hearing loss and branch retinal artery occlusion. Autoimmune endotheliopathy of the eye results in branch retinal vein occlusions, which can manifest as scotomas and a reduction in visual acuity. Autoimmune endotheliopathy of the brain results in encephalopathy, which can manifest as headaches, changes in behaviour and cognitive impairment. Finally, autoimmune endotheliopathy of the inner ear can present with tinnitus, hearing loss and vertigo (3). Recurrence of symptoms can vary, with complete remission, frequent relapses and continuous courses of illness having all been reported (4).
Diagnosis
Whilst there are no definitive criteria for diagnosis of Susac syndrome, diagnosis is largely based on history to guide clinical suspicion, and evidence of brain, retina and/or inner ear involvement. Patients with episodes of hearing changes, visual disturbance and severe headaches should be suspected of having Susac syndrome. A magnetic resonance imaging test of the brain may demonstrate microinfarcts of the corpus callosum, which are described as ‘snowball lesions’ and characteristic of Susac syndrome. To demonstrate retinal involvement, fluorescein angiography can be performed to identify branch retinal artery occlusion. Finally, to investigate involvement of the inner ear, an audiogram can be performed to demonstrate sensorineural hearing loss (2,4). It is important to exclude differential diagnoses which may present similarly to Susac syndrome, including multiple sclerosis, Meniere’s disease and acute disseminated encephalomyelitis (3).
Management
Management of Susac syndrome is with immunosuppressive medications, including corticosteroids and biologics. It is important to initiate treatment early to reduce risk of disease progression and chance of relapse. It is important to counsel patients that relapses may occur, to allow for early identification and treatment (3,4).
References
- Nazari F, Azimi A, Abdi S. What is Susac syndrome? — A brief review of articles. Iran J Neurol. 2014 Oct 6;13(4):209–14. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC4300795/
- National Organization for Rare Disorders (NORD). Susac Syndrome. NORD Rare Disease Database [Internet]. [cited 2025 Sep 07]. Available from: https://rarediseases.org/rare-diseases/susacs-syndrome/
- Cleveland Clinic. Susac syndrome [Internet]. Cleveland Clinic; 2023 [cited 2025 Sep 7]. Available from: https://my.clevelandclinic.org/health/diseases/15073-susac-syndrome
- Kini A, Pham G. Susac Syndrome [Internet]. EyeWiki; 2025 [cited 2025 Sep 7]. Available from: https://eyewiki.org/Susac_Syndrome