What is Susac syndrome?
Susac syndrome is a rare, autoimmune condition that affects the small blood vessels of the brain, retina and inner ear. The condition is characterized by three main symptoms:
- Encephalopathy (for other causes of encephalopathy, read about Guillain-Barre syndrome)
- Sensorineural hearing loss
- Vision loss
These symptoms usually are not present when the syndrome first occurs, but they develop with time. This syndrome is not easy to diagnose, because the main characteristic symptoms might not occur at the same time and there is often multi-system involvement which mimics other conditions, like Meniere’s syndrome. Susac syndrome mostly affects women, at the age between 20 and 40 years, but it can also affect men .
The exact cause of Susac syndrome is still unknown. It is known that this syndrome occurs due to the malfunction of immune system. The immune system attacks the cells of the inner lining of blood vessels in the brain, retina and inner ear. This causes the swelling of the cells and blockage of the blood vessels, which results in lack of oxygen and nutritional supply to the affected organs . If you want to learn about other autoimmune diseases, read about Lambert-Eaton syndrome, Stiff person syndrome.
The most common symptom of Susac syndrome is headache. It might appear several months before any signs of encephalopathy with psychiatric disturbances, such as:
- Changes in behavior
- Cognitive chances
- Memory loss
- Dementia (also see Charles-Bonnet syndrome)
Other signs of neurological involvement include:
- Dysarthria- major speech disturbance, when the patient has trouble pronouncing and it is difficult to understand what they are saying
- Dysmetria-lack of coordination of movement
- Vertigo, trouble walking
- Crania nerve involvement
- Cauda equina syndrome
Most common ocular manifestations are branch retinal artery occlusions (BRAO). This retinal blood vessel involvement usually affects both eyes and is widely spread in the retina. BRAOs cause scotoma (partial loss of vision or a blind spot) or photopsias (flashes of light in the vision field).
Upon examination there is usually an area of infarction in the retina. Other signs that can be found include:
- Cotton wool spots
- Occlusion of the retinal artery
- Areas with arterio-arterial collaterals in retina
- Formation of functional microscopic blood vessels in the optic disc
- Macular edema
- Rarely- retinal blood hemorrhages, venous-venous collaterals
- Retinal “leakage”- due to loss of blood vessel wall integrity, when performing fluorescein angiography the fluorescein leaks .
The typical manifestation is cochlear and end-arteriole occlusion. Hearing loss can affect one or both ears. The hearing loss is asymmetrical .
Usually cerebrospinal fluid is examined. Elevated protein levels and lymphocytic pleocytosis (abnormally large level of lymphocytes) can be found. If IgG index is increased, it might be confused with possible multiple sclerosis.
Other findings in blood analysis include:
- Positive tests for antinuclear and antiphospholipid antibodies, like in antiphospholipid antibody syndrome.
- Elevated VIII coagulation factor and Willebrand factor antigens
Magnetic resonance imaging is usually the method of choice. In MRI typical findings are:
- Multiple small, hyper-intense focal lesions in corpus callosum, cerebellum and midbrain
- Linear defects, also known as spikes in corpus callosum
- In subacute stages of the disease there can be callosal “holes” .
Another imaging study to determine the condition of ocular blood vessels is fluorescein angiography. The typical signs of this imaging study are:
- White spots in the retina- cotton wool sports
- Caused by injury due to lack of blood flow
- Blockage of retinal blood vessels
- Increased blood vessel wall staining[2,4]
In order to diagnose Susac syndrome, brain biopsy might be performed. Brain tissue examination shows inflammation around the small blood vessels and microscopic infarctions of the brain tissue. The presence of necrosis in small blood vessels suggests the presence of vasculopathy rather than vasculitis.
Susac syndrome can be a self-limiting disease- it often stabilizes in 2 to 4 years. In some cases a complete remission occurs and patients fully recover. Still, in some cases this syndrome becomes chronic and can recur. Mostly patients experience episode, lasting more than a year, but with no recurrence. During this episode the patient might get a permanent CNS damage, with dementia and loss of motor function, therefore encephalopathy is usually treated aggressively. The three general clinical courses of Susac syndrome are:
- Monocyclic – an episode lasting 1-2 years, usually remitting
- Polycyclic disease- remission is seen between multiple episodes and lasts more than 2 years
- Chronic continuous disease- when no remission is observed for more than 2 years.
Since Susac syndrome is a rare disease, there have been no randomized controlled clinical trials to determine the most effective course of treatment. The data available on the best treatment options mostly comes from individual cases. Now it has been widely recognized that the first line of therapy is high dose corticosteroids. Some other immunomodulatory agents are used:
- Intravenous immunoglobulin
- Plasma exchange
- Mycophenolate mofetil
Mostly a combination of some of these agents is used.
When Susac syndrome presents with encephalopathy, it must be treated aggressively with intravenous corticosteroids, followed by addition of other agents and slowly switching to oral corticosteroids. The use of immunomodulatory drugs might be necessary for more than 2 years after symptom remission.
For patients with continuous relapses monoclonal antibody treatment in some cases has been successful.
In the acute phase, hearing loss can be treated with injections of dexamethasone. Patients with hearing loss usually require cochlear implants.
Visual deficits are mostly also treated with immunotherapy (also used for treating Sezary syndrome). For ocular manifestations the aim of immunotherapy is to prevent retinal infarcts since damage to the retina is permanent and irreversible. In early stages, hyperbaric oxygen therapy has shown some improvements. If retinal ischemia and neovascularization occurs, photocoagulation can be used.
Prognosis of Susac syndrome depends on the clinical course of the syndrome. Around 50% of the patients already have cognitive impairment until the correct diagnosis has been established and aggressive treatment has been started. However, many patients recover completely, or with insignificant brain damage, even though upon the initial assessment encephalopathy was significant .
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- General information for patients and health specialists: https://rarediseases.info.nih.gov/diseases/7713/susac-syndrome
- Causes of Susac syndrome: http://my.clevelandclinic.org/health/articles/susac-syndrome
- Clinical manifestations of Susac syndrome: http://www.sciencedirect.com/science/article/pii/S1568997214000500
- Imaging studies: https://radiopaedia.org/articles/susac-syndrome
- Clinical course: http://www.forgottendiseases.org/assets/Susac_Syndrome.html
- Treatment developments: http://www.acnr.co.uk/2013/03/new-developments-in-susacs-syndrome/