What Is Susac Syndrome

Susac syndrome 

Susac Syndrome is a rare but potentially debilitating autoimmune disorder that primarily affects the brain, retina, and inner ear. The main distinguishing factors of the syndrome are impaired brain function, partial or complete blockage of blood flow to the retinas and inner ear diseases such as hearing loss. 

First identified by Dr John Susac in 1979,¹ the syndrome has since gained attention for its distinct triad of symptoms - encephalopathy, branch retinal artery occlusion, and sensorineural hearing loss. It is an autoimmune condition that damages the microvasculature of the brain, causing swelling in the damaged areas. This leads to occlusions and blockages within the blood vessels, restricting blood flow and causing less oxygen to reach these vital organs and causing permanent damage.^1,2 

While it remains a challenging condition to diagnose and manage, advancements in research and clinical understanding are shedding light on potential treatment avenues and management strategies for affected individuals.

Symptoms and clinical presentation

The onset of Susac Syndrome can vary widely, making it difficult for doctors to diagnose. Common symptoms include a combination of neurological manifestations such as headache, cognitive impairment, and behavioural changes. It can affect the psyche and cause paranoia and changes in personality due to brain damage. Brain retinal artery occlusion (BRAO) is a condition involving visual disturbances, including blurred vision, visual field defects, and even blindness. These symptoms are called scotoma and are caused by blocked blood flow. The neurological symptoms vary from person to person and depend on how long they have been suffering from the syndrome.³

Additionally, patients may experience varying degrees of hearing loss, often accompanied by tinnitus or vertigo due to inner ear issues. The cochlea, which is responsible for converting sound into nerve impulses to the brain, becomes damaged due to the lack of blood flow, resulting in hearing issues.⁴

Diagnosis

Diagnosing Susac Syndrome often requires a comprehensive approach involving a thorough clinical assessment, neuroimaging studies, audiological examinations, and ophthalmological evaluations. This is because it is very easy to misdiagnose due to many disorders existing with similar symptoms. 

The most promising tests involve Magnetic Resonance Imaging (MRI) of the brain. Often, patients with this syndrome have multiple small areas of abnormality in the white matter of the brain, indicating damage to the smallest blood vessels (microangiopathy). These are referred to as “snowball” lesions.⁵

Another promising test is ophthalmic examinations, which often show evidence of retinal artery occlusions, while audiometry may confirm the presence of hearing loss caused by damage to the hair cells in the ear (sensorineural hearing loss).

A fluorescein angiogram is a very useful diagnostic test because it gives in-depth imagery of the circulation within the eye and retina using a special dye and can help detect BRAO.

Recent research has suggested that BRAO develops due to an autoimmune mechanism involving endothelial cells and the blood-brain barrier. Immunological studies have identified the presence of autoantibodies (produced when the body’s immune system attacks itself), suggesting a potential role of the immune system in the development of the syndrome.⁶

Management and treatment: 

While there is no definitive cure for Susac Syndrome, early recognition and prompt initiation of appropriate treatment are crucial in preventing long-term complications. 

The symptoms of brain damage subside on their own after 1-3 years and whilst treatment is recommended to minimise damage, the symptoms will go away without it.³

Treatment regimens often include a combination of immunosuppressive therapies such as corticosteroids, mycophenolate mofetil, or cyclophosphamide to suppress the autoimmune response. Relief for hearing loss and visual disturbances may require a multidisciplinary approach, including the use of hearing aids and low-vision aids, depending on the severity of the impairments. If the hearing-loss is profound then cochlear implantation is encouraged.⁴

Prognosis and future research

The prognosis of Susac Syndrome varies among individuals, with some experiencing spontaneous recovery while others may face long-term neurological deficits. With the advancement of research in immunology and neurology, there is an increasing focus on identifying specific biomarkers and targeted therapies that can potentially manage the progression of the disease and improve long-term health for patients.

Conclusion

Susac Syndrome, though rare, presents a significant challenge due to its diverse manifestations and potential long-term neurological consequences. Continued research efforts aimed at finding the underlying causes and refining treatment strategies show promise in improving the prognosis and quality of life for individuals affected by this complex autoimmune disorder. Increased awareness, early recognition, and multidisciplinary management are paramount in providing comprehensive care and support for those living with Susac Syndrome.