About susac syndrome
What is susac syndrome?
Susac's syndrome is a rare disorder characterized by three main problems: impaired brain function (encephalopathy), partial or complete blockage (occlusion) of the arteries that supply blood to the retina (branch retinal artery occlusion, or BRAO), and inner ear disease (hearing loss, most notably).
Three main forms of Susac's syndrome have become apparent. In one form, encephalopathy is the main problem. In the second form, BRAO and hearing loss are the main problems, and there is little or no brain disease. In the third form, encephalopathy is the main problem in the beginning, but recurrent episodes of BRAO and hearing loss become the main problem after the encephalopathy goes away.
The encephalopathic form of Susac's syndrome often resolves spontaneously (often going away within 1 years), even without treatment (self-limited); the other forms tend to follow a more prolonged, more chronic course (3-10 years, or more).
Although considered rare, Susac's syndrome is being recognized more often worldwide and its true frequency in the general population is unknown. This is because the disorder may be misdiagnosed as multiple sclerosis.
Susac's syndrome is an autoimmune disease---specifically, an autoimmune endotheliopathy. "Autoimmune" means that a person's own immune system is mistakenly attacking one's own healthy tissue. An "endotheliopathy" is any disorder that involves injury to the endothelium, which is the thin layer of cells that line the inner walls of blood vessels. In Susac's syndrome, the person's own immune system is mistakenly attacking the endothelial lining of the smallest blood vessels (the capillaries, venules and arterioles) in the brain, retina, and inner ear. When the endothelial cells become injured, they tend to swell, and this endothelial cell swelling plays a key role in the partial or complete occlusion (blockage) of the tiny vessels in the brain, retina and inner ear. This blockage results in decreased blood flow through the vessels and, therefore, decreased delivery of oxygen and nutrients to the brain, retina, and inner ear---causing these three organs to suffer.
What are the symptoms for susac syndrome?
The specific symptoms, severity, and outcome of Susac syndrome vary from one person to another. Commonly, the three main features (encephalopathy, branch retinal arterial occlusions, and hearing loss) are not all present at disease onset, and all three do not necessarily develop in all patients. When patients are first evaluated by a physician, any one of the three main features may be the only feature present, with one or both of the other features appearing only later.
In many patients, Headaches (including migraine-like headaches) precede the development of other symptoms of Susac syndrome. A variety of additional neurological findings may develop: cognitive dysfunction (including memory loss, confusion, and decreased executive function), gait disturbance, and slurred speech (dysarthria). Some individuals develop psychiatric symptoms such as paranoia or personality or behavioral changes. The specific neurological symptoms that develop will vary from one person to another.
Branch retinal artery occlusion (BRAO) can cause the patient to notice a “dark spot” or “ area” in their field of vision; or, some patients describe a “curtain or shade being drawn” over a portion of their vision. The medical term for these symptoms is “scotoma.” These symptoms are due to injury to the retina, because of blocked blood flow. The retina is the thin layer of nerve cells that sense light and convert it to nerve signals, which are then relayed to the brain through the optic nerve. Both eyes can be affected in individuals with Susac syndrome. Permanent impairment of vision may occur. BRAOs may occur early in some individuals or later in the course of the disease in others.
Many individuals with Susac syndrome develop Hearing loss due to damage to the small, snail-shaped organ of the inner ear known as the cochlea. The cochlea converts sound into nerve impulses to be sent to the brain. The damage to the cochlea is caused by the blockage of blood flow through the small vessels that supply blood to the cochlea. Hearing loss in Susac syndrome is primarily at low frequencies and usually occurs relatively suddenly. It may affect both ears (bilateral). Its severity can range from mild to severe. In severe cases, cochlear implantation is warranted. In some cases, Hearing loss may occur before other symptoms of Susac syndrome develop. Hearing loss is often accompanied by intense ringing of the ears (tinnitus). The vestibular apparatus, which is also located in the inner ear, can also be affected by the microvascular endotheliopathy of Susac’s syndrome, resulting in vertigo (dizziness).
The encephalopathic form of Susac syndrome is typically self-limited (i.e., eventually subsides on its own), but may take a long time to resolve and may recur. It usually runs a course of 1-3 years, during which time individuals may experience fluctuating levels of symptoms (relapsing-remitting). Although the encephalopathic form eventually goes away on its own, treatment is necessary to prevent or minimize damage that can occur while the disease is active. Relapse after a long period of remission is rare, but can occur.
What are the causes for susac syndrome?
Susac syndrome is an autoimmune endotheliopathy, a disorder in which the body’s immune system mistakenly attacks the inside lining (endothelium) of the walls of the very tiny blood vessels that supply blood to the brain, retina, and inner ear. The exact, underlying reason why this occurs is unknown. Why the microvasculature in the brain, retina, and inner ear are primarily affected is also unclear. The skin may also be involved.
What are the treatments for susac syndrome?
Although Susac syndrome can sometimes spontaneously subside, early, appropriately aggressive and appropriately sustained treatment is needed, while the disease is active, to avoid or minimize potential irreversible damage to the brain, retina, and inner ear.
What are the risk factors for susac syndrome?
Susac syndrome primarily affects young women between the ages of 20-40, but has occurred in individuals ranging in age from 9 to 72. Women are affected three times more often than men. Although considered a rare disorder, Susac syndrome is being recognized more often worldwide and may be more common than originally thought. However, because the disorder often goes unrecognized or misdiagnosed, determination of the true frequency of Susac syndrome in the general population has been difficult.
So far, Susac syndrome has not been proven to occur more frequently in any particular ethnic group—but, early data suggest that it may occur more commonly in Caucasian population groups. It has not been known to occur in more than one member of any family, even when the extended family is taken into account.
Susac syndrome was first reported in the medical literature in 1979 by Dr. John Susac. It has also been referred to as “retinopathy, encephalopathy, deafness associated microangiopathy (RED-M)” or “small infarctions of cochlear, retinal and encephalic tissue (SICRET).”
Is there a cure/medications for susac syndrome?
The two current mainstays of therapy are medications that suppress the activity of the immune system (immunosuppressive agents)—corticosteroid (e.g. prednisone) and intravenous immunoglobulins (IVIG). Additional drugs may also be necessary. Additional drugs that have been used to treat individuals with Susac syndrome include mycophenolate mofetil (Cellcept), azathioprine (Imuran), cyclophosphamide, rituximab, and anti-TNF therapies. Treatment choices depend on the severity of the disease.
For individuals with significant hearing loss, a hearing aid may be indicated. For those with profound hearing loss, cochlear implantatio may be beneficial.