Clinical Pearls & Morning Reports
Hearing loss and tinnitus are very common features of Susac’s syndrome because there is a strong predilection for microangiopathy of the cochlea. In addition, vestibular abnormalities are common. Read the latest NEJM Case Records of the Massachusetts General Hospital here.
Q: What is the clinical triad that characterizes Susac’s syndrome?
A: Susac’s syndrome is an acquired autoimmune disorder that causes microangiopathy of the retina, cochlea, and brain. In its complete form, it is characterized by a clinical triad of vision loss due to branch retinal artery occlusions, sensorineural hearing loss, and neurologic dysfunction. However, only a minority of patients present with the full triad. Although partial presentations are common, there is often a delay in diagnosis until the complete syndrome develops. Some patients present with isolated retinal findings, others with isolated tinnitus and hearing loss, and a few with isolated encephalopathy that mimics such conditions as acute demyelinating encephalomyelitis. In an evaluation for Susac’s syndrome, a funduscopic examination is key to identifying retinal ischemia that is asymptomatic.
Q: Are there any biomarkers that aid in the diagnosis of Susac’s syndrome?
A: There are currently no biomarkers that can be used to establish a definitive diagnosis of Susac’s syndrome. A study has evaluated the pathogenic role and diagnostic value of anti–endothelial-cell antibodies in serum in Susac’s syndrome, but to date, an assay has not been sufficiently validated for clinical purposes.
A: The presence of lesions in the central corpus callosum on MRI would support the diagnosis of Susac’s syndrome. The central corpus callosum is supplied by small-caliber vessels, which make it a site of preferential involvement in Susac’s syndrome, and the pattern of involvement differs from that seen in other inflammatory brain diseases, such as multiple sclerosis. Susac’s syndrome may be associated with involvement of the deep gray matter (in 70% of cases), parenchymal enhancement (70%), and leptomeningeal enhancement (33%).
A: There are limited data to inform the treatment of Susac’s syndrome, and we cannot rely on a well-delineated mechanism of disease to guide treatment, because the precise mechanism by which this immune-mediated endotheliopathy develops is unclear. However, therapies that target both B cells and T cells have shown efficacy in preventing or at least mitigating the accumulation of further microangiopathic disease. Surveillance for subclinical relapse can include serial audiometry, fluorescein angiography, and MRI of the head, including assessment of midsagittal, diffusion-weighted, contrast-enhanced images, which show the corpus callosum. The frequency with which these studies should be undertaken in clinically stable or asymptomatic patients has not been established, but repeat automated perimetry, fluorescein angiography, and MRI are recommended at 1 and 3 months after initial presentation, at a minimum. There are no predictors of relapse.