Susac-Syndrom: Eine interdisziplinäre Herausforderung

Susac Syndrome: an uncommon cause of impaired vision

A 35-year-old Caucasian woman presented an abrupt onset of bilateral impaired vision, and arrived to our attention two weeks later. She had a previous episode of mild dizziness. She underwent a fluorescein angiography showing branch retinal artery occlusions and a brain magnetic resonance imaging (MRI) revealing several supraand infratentorial FLAIR-hyperintense white matter lesions, two with contrast enhancement. Thrombophilic, autoimmune and infective (including Human Immunodeficiency Virus, Borrelia burgdorferi, Hepatitis B Virus, Hepatitis C Virus, Herpes Simplex Virus 1-2, Varicella Zoster Virus) screening was negative. Cerebrospinal fluid analysis showed intrathecal IgG synthesis. We suspected a Primary Central Nervous System Vasculitis, and intravenous steroids were started. Three months later a second brain MRI showed seven new lesions without contrast enhancement, and she revealed a cognitive impairment and bilateral hearing loss. Reviewing the clinical history and MRI, she fulfilled diagnostic criteria for Susac syndrome. She had two cycles of cyclophosphamide, and recovered in 6 months and then remained stable with metotrexate.

[Susac syndrome-interdisciplinary tracking of the chameleon: two different case reports]

BACKGROUND

The diagnosis of Susac syndrome, a presumed autoimmune retinocochleocerebral microvasculopathy, is extremely complex. At the onset of this orphan disease patients can present with an incomplete clinical triad consisting of sensorineural hearing loss, visual loss because of retinal ischemia and diverse neurological symptoms. In terms of the pathophysiology, it is assumed that the vascular endothelial cells swell, occlude the lumina of the vessels and consequently cause ischemia in the surrounding tissue. Due to the wide range of symptoms it is extremely challenging to establish a correct diagnosis. Susac syndrome should be considered as an important differential diagnosis from other neurological, ophthalmological, psychological and otorhinolaryngological diseases.

CASE REPORT

This report presents two different courses of the disease in patients with Susac's syndrome. The first case of a 46-year-old woman, with previously confirmed Susac's syndrome, describes the treatment adjustment and monitoring. The second case of a 30-year-old woman shows the establishment of the initial diagnosis.

DISCUSSION

The two reported cases of Susac's syndrome show the multifaceted range of clinical findings and courses of the disease. Furthermore, the diagnostic and therapeutic options are discussed with respect to the current literature. Diagnostic criteria already published by the European Susac Consortium and a good interdisciplinary collaboration enable a diagnosis as early as possible, which is essential for avoiding delayed treatment and reducing morbidity.

Otologic manifestations of Susac syndrome

Susac syndrome, a rare autoimmune disorder first described as a classic triad (encephalopathy, branch retinal artery occlusion, and sensorineural hearing loss) in 1979 by renowned physician John O. Susac, has been an advancing area of clinical interest and scientific research over the last several decades. This comprehensive review aims to succinctly highlight the breadth and detail of this enigmatic disease, with a primary focus on otologic manifestations. Topics discussed include epidemiology, pathophysiology, clinical manifestations, differential diagnoses, classification schema, laboratory investigations, characteristic audiometric findings, high-yield radiographic imaging, temporal bone histopathology, treatment strategies and overall prognosis.

Anatomical and functional correlation in Susac syndrome: multimodal imaging assessment

Background

Susac’s syndrome (SuS) is an uncommon disease characterized by retinal microangiopathy that may be assessed more accurately with optical coherence tomography angiography (OCTA), a new imaging technique which provides a retinal microvasculature map. The purpose of this case report is to describe the multimodal imaging findings of SuS correlating OCTA with functional tests.

Case presentation

Retrospective review of one case with clinical and imaging evidence of SuS. Color fundus photograph, fluorescein angiography (FA), OCTA, microperimetry (MP) and visual field (VF) tests were analyzed at the time of presentation and at 1- and 6-month visit following initiation of treatment. The study patient underwent standard treatment for SuS. The patient age was 31 year-old and the baseline visual acuity was 20/60 and 20/20 in the right and left eyes, respectively. At presentation, FA showed branch retinal arterial occlusion within the macular area of the right eye and vascular leakage in the periphery of the left eye. OCTA demonstrated areas of superficial and deep retinal vascular plexuses hypoperfusion in both eyes. The OCTA segmentations in the outer retina and choriocapillaris were normal. The low VF and MP sensitivity signals precisely corresponded to the topography of decreased vascular perfusion seen on the OCTA density map in both eyes. Six months after specific SuS therapy, retinal vascular perfusion showed partial improvement in both eyes.

Conclusion

OCTA may demonstrate superficial and deep retinal vascular non-perfusion without choriocapillary vasculature changes in SuS. This anatomical information given by OCTA corresponded to points of low sensitivity on functional tests represented by VF and MP.

Ultrahigh field MRI in clinical neuroimmunology: a potential contribution to improved diagnostics and personalised disease management

Conventional magnetic resonance imaging (MRI) at 1.5 Tesla (T) is limited by modest spatial resolution and signal-to-noise ratio (SNR), impeding the identification and classification of inflammatory central nervous system changes in current clinical practice. Gaining from enhanced susceptibility effects and improved SNR, ultrahigh field MRI at 7 T depicts inflammatory brain lesions in great detail. This review summarises recent reports on 7 T MRI in neuroinflammatory diseases and addresses the question as to whether ultrahigh field MRI may eventually improve clinical decision-making and personalised disease management.

[Ultrahigh field MRI in context of neurological diseases]

Ultrahigh field magnetic resonance imaging (UHF-MRI) has recently gained substantial scientific interest. At field strengths of 7 Tesla (T) and higher UHF-MRI provides unprecedented spatial resolution due to an increased signal-to-noise ratio (SNR). The UHF-MRI method has been successfully applied in various neurological disorders. In neuroinflammatory diseases UHF-MRI has already provided a detailed insight into individual pathological disease processes and elucidated differential diagnoses of several disease entities, e.g. multiple sclerosis (MS), neuromyelitis optica (NMO) and Susac's syndrome. The excellent depiction of normal blood vessels, vessel abnormalities and infarct morphology by UHF-MRI can be utilized in vascular diseases. Detailed imaging of the hippocampus in Alzheimer's disease and the substantia nigra in Parkinson's disease as well as sensitivity to iron depositions could be valuable in neurodegenerative diseases. Current UHF-MRI studies still suffer from small sample sizes, selection bias or propensity to image artefacts. In addition, the increasing clinical relevance of 3T-MRI has not been sufficiently appreciated in previous studies. Although UHF-MRI is only available at a small number of medical research centers it could provide a high-end diagnostic tool for healthcare optimization in the foreseeable future. The potential of UHF-MRI still has to be carefully validated by profound prospective research to define its place in future medicine.

Susac's syndrome--pathogenesis, clinical variants and treatment approaches

Susac's syndrome is a rare disease that is characterised by the clinical triad of encephalopathy, branch retinal artery occlusion, and sensorineural hearing loss. It was first described as a distinctive syndrome by Susac in 1979. There have been 304 reported individual patients with Susac's syndrome. Etiopathogenesis is not clear, although it is now thought that it is an immune-mediated endotheliopathy that affects the microvasculature of the brain, retina, and inner ear. Antiendothelial cell antibodies (AECAs) play an important role in mediating the endothelial cell injury with consequent deposition of thrombotic material in the lumen of the small vessel. In biopsies of the brain, microinfarcts with atrophy of the white and grey matter could be detected. These microinfarcts are caused by a microangiopathic process with arteriolar wall proliferation, lymphocytic infiltration and basal lamina thickening. At clinical onset, the most common manifestation was central nervous system symptoms, followed by visual symptoms and hearing disturbances. Diagnosis is based on Magnetic Resonance Imaging (MRI), retinal fluorescein angiography, and audiometry; these are considered crucial tests to enable diagnosis. Antiendothelial cell antibodies (AECAs) are also of diagnostic relevance. Based on the hypothesis of being an autoimmune disease, treatment has to be immunosuppressive. In addition, anticoagulation measures, antiplatelet agents and antivasospastic agents should be considered. The majority of patients did not initially present with the complete triad of symptoms. An appropriate approach would be to perform a search for absent components of the triad if the clinical presentation is suggestive of Susac's syndrome. Improved understanding of the presentation of Susac's syndrome will prevent misdiagnosis and ensure that patients receive the best possible care.

Clinical, paraclinical and serological findings in Susac syndrome: an international multicenter study

Background

Susac syndrome (SuS) is a rare disorder thought to be caused by autoimmune-mediated occlusions of microvessels in the brain, retina and inner ear leading to central nervous system (CNS) dysfunction, visual disturbances due to branch retinal artery occlusions (BRAO), and hearing deficits. Recently, a role for anti-endothelial cell antibodies (AECA) in SuS has been proposed.

Objectives

To report the clinical and paraclinical findings in the largest single series of patients so far and to investigate the frequency, titers, and clinical relevance of AECA in SuS.

Patients and methods

A total of 107 serum samples from 20 patients with definite SuS, 5 with abortive forms of SuS (all with BRAO), and 70 controls were tested for AECA by immunohistochemistry employing primate brain tissue sections.

Results

IgG-AECA >1:100 were detected in 25% (5/20) of patients with definite SuS and in 4.3% (3/70) of the controls. Median titers were significantly higher in SuS (1:3200, range 1:100 to 1:17500) than in controls (1:100, range 1:10 to 1:320); IgG-AECA titers >1:320 were exclusively present in patients with SuS; three controls had very low titers (1:10). Follow-up samples (n = 4) from a seropositive SuS patient obtained over a period of 29 months remained positive at high titers. In all seropositive cases, AECA belonged to the complement-activating IgG1 subclass. All but one of the IgG-AECA-positive samples were positive also for IgA-AECA and 45% for IgM-AECA. SuS took a severe and relapsing course in most patients and was associated with bilateral visual and hearing impairment, a broad panel of neurological and neuropsychological symptoms, and brain atrophy in the majority of cases. Seropositive and seronegative patients did not differ with regard to any of the clinical or paraclinical parameters analyzed.

Conclusions

SuS took a severe and protracted course in the present cohort, resulting in significant impairment. Our finding of high-titer IgG1 and IgM AECA in some patients suggest that humoral autoimmunity targeting the microvasculature may play a role in the pathogenesis of SuS, at least in a subset of patients. Further studies are warranted to define the exact target structures of AECA in SuS.

[Diagnosis and monitoring of multiple sclerosis: the value of optical coherence tomography]

Besides the relapse rate and neurological examination, magnetic resonance imaging (MRI) plays a key role in multiple sclerosis (MS) monitoring. However, MRI is costly and even in Germany not always readily available. Additionally, routine MRI scans are not sensitive enough regarding differentiation between demyelination and neurodegeneration and show a discrepancy between lesion load and the degree of disability. In contrast, optical coherence tomography (OCT) is a validated non-invasive method for the quantification of neurodegenerative processes in the retina, as they appear in MS and other neurological diseases. The OCT is inexpensive, easy to handle and highly reproducible. Additionally, it is well tolerated and thus represents a promising tool for monitoring of neurodegenerative disorders. This article describes in detail the OCT technique and its usefulness for both diagnosis and monitoring of MS.

Lesion morphology at 7 Tesla MRI differentiates Susac syndrome from multiple sclerosis

Background:

Although an orphan disease with still obscure aetiopathogenesis, Susac syndrome has to be considered as differential diagnosis in multiple sclerosis (MS), since its clinical presentation and paraclinical features including routine magnetic resonance imaging (MRI) findings partially overlap.

Objective:

We aimed to study a potential benefit of 7T MRI for (i) the differentiation between Susac syndrome and MS and (ii) the clarification of pathogenesis of Susac syndrome.

Methods:

Five patients suffering from Susac syndrome, 10 sex- and age-matched patients with relapsing–remitting MS (median Expanded Disability Status Scale (EDSS) score 1.5) and 15 matching healthy controls were investigated at 7 Tesla MRI. The protocol included T1-weighted MPRAGE, T2*-weighted FLASH, and TIRM sequences.

Results:

Almost all T2* FLASH lesions in patients with MS were centred by a small central vein (325 lesions; 92%) and often showed a small hypointense rim (145 lesions; 41%). In contrast, white matter lesions in Susac syndrome exhibited a perivascular setting significantly less frequently (148 lesions; 54%, p=0.002), and very rarely exhibited a hypointense rim (12 lesions; 4%, p=0.004). Furthermore, in addition to callosal atrophy, Susac patients showed cerebrospinal fluid-isointense lesions within the central part of corpus callosum that are not commonly seen in MS.

Conclusion:

At 7T MRI, plaques in MS patients and patients with Susac syndrome differed substantially with respect to morphology and pattern. Thus, lesion morphology at 7T (i) may serve as a marker to distinguish Susac syndrome from MS and (ii) reflects a different pathophysiological mechanism underlying Susac syndrome, for example microinfarction rather than demyelination.