Susac's Syndrome: A Tale of Disability Due to Late Recognition

Abstract

Susac's syndrome is a rare inflammatory microangiopathy characterized by the triad of retinopathy, encephalopathy, and hearing loss. The syndrome causes recurrent microinfarcts in these organs, which in turn manifests with repeated attacks of visual field loss, hearing loss and tinnitus, and various brain syndromes. These often lead to the significant accumulation of disability over time, particularly if there is a delay or failure in diagnosis. The brain lesions associated with this condition may resemble those of multiple sclerosis, especially to those who are unfamiliar with the disease and its distinctive clinical and radiological features. Such misdiagnosis may have grave clinical consequences. Here, we present the case of a 41-year-old Danish man who presented with the classical triad of Susac's syndrome but was misdiagnosed with multiple sclerosis. It took three years from disease onset before the eventual diagnosis was recognized, and by this time, he had accrued a lot of neurological deficits. With this case report, we aim to draw awareness to this rare but unforgiving entity which if missed can lead to the accumulation of disabilities. We also aim to emphasize the features that help distinguish it from multiple sclerosis, the condition with which it is most often confused.

Keywords: brain microinfarcts; brain white matter lesions; brain-eye-ear syndromes; branch retinal artery occlusion; sudden sensorineural hearing loss (ssnhl); sudden vision loss; susac's syndrome.

Figure 1. Brain MRI at the initial presentation in August 2020

(1A) A tiny FLAIR hyperintensity (arrow) in the deep white matter of the right hemisphere. (1B) A T2-weighted image showing a faint icicle lesion (arrow) in the posterior aspect of the corpus callosum. (1C) A T2-weighted image showing a small snowball lesion (a pathognomonic feature of Susac's syndrome) in the middle of the splenium of the corpus callosum. (1D) DWI with three tiny lesions in the splenium of the corpus callosum showing diffusion restriction. (1E and 1F) Other lesions showing diffusion restriction in the left and right hemisphere white matter, respectively. (1G) Post-contrast T1-weighted imaging showing a faint enhancement in the left internal capsule FLAIR: fluid-attenuated inversion recovery; DWI: diffusion-weighted imaging

Figure 2. Brain MRI in March 2022 after the appearance of new symptoms

(2A) A small new lesion in the left temporal lobe demonstrating a hyperintense signal on the FLAIR sequence (arrow). (2B) The same lesion showing diffusion restriction on the diffusion-weighted sequence. (2C) Some of the old lesions showing from August 2020, showing gliotic features on the FLAIR sequence FLAIR: fluid-attenuated inversion recovery

Figure 3. Brain MRI in August 2022 showing the development of a new set of lesions

(3A) A new T2 hyperintense white matter lesion in the right superior frontal gyrus (arrow). (3B) Another new hyperintense lesion in the genu of the corpus callosum seen on the axial FLAIR image. (3C) The same image in 3B shown on T2-weighted coronal images. (3D) Another white matter lesion in the right parietal subcortical white matter, showing diffusion restriction. (3E) Yet another white matter lesion in the right cerebellar hemisphere showing diffusion restriction. (3F) One more new lesion in the right periventricular white matter showing diffusion restriction FLAIR: fluid-attenuated inversion recovery

Figure 4. Brain MRI in December 2022 showing newly appearing lesions

(4A) An obvious FLAIR hyperintense lesion in the left anterior thalamus. (4B) Multiple lesions in the periventricular and deep white matter showing diffusion restriction. (4C) One lesion in each of the cerebellar hemispheres showing diffusion restriction. (4D, 4E, and 4F) Multiple small lesions in the subcortical and deep white matter FLAIR: fluid-attenuated inversion recovery

Figure 5. Pure tone audiogram in September 2023 after supposed clinical remission

Notice the hearing loss in both ears, particularly in the lower frequencies