Susac’s Syndrome (SuS) is a rare autoimmune disorder in which a person’s own immune system is mistakenly attacking the lining of the smallest blood vessels in the brain, the retina of the eye and inner ear. When these vessels are attacked, they become injured and tend to swell, resulting in decreased blood flow (as well as oxygen and nutrients) to the brain, retina and inner ear.
As a result, a person with SuS will experience any or a combination of three main health issues: impaired brain function (encephalopathy), partial or complete blockage (occlusion) of the arteries that supply blood to the retina (called branch retinal artery occlusion, or BRAO), and inner ear disease, usually manifesting as hearing loss.
Researchers have identified three forms of SuS:
- Encephalopathy is the patient’s main problem;
- BRAO and hearing loss are predominant with little or no brain disease;
- Encephalopathy is predominant in the beginning, but episodes of BRAO and hearing loss become more prevalent after the encephalopathy resolves.
The encephalopathic form often resolves spontaneously within one to three years (during this time the severity will vary), while other forms have a longer, more chronic nature with frequent flare-ups. In all forms, treatment that suppresses the immune system is required as long as the disease is active.
SuS was first reported by Dr. John Susac in 1979, yet there is not a lot of available information about SuS and the disease is often mistaken for atypical multiple sclerosis (MS), atypical acute disseminated encephalomyelitis (ADEM) or central nervous system vasculitis. For this reason, SuS is believed to be more common than the 313 cases reported to date worldwide.
SuS primarily affects young women aged 20 to 40 (women are affected three times more often than men), but it also affects men, adolescents and children (about 11 percent of cases have been in children, mostly older adolescents). Thus far, SuS does not appear to affect one ethnic group more than any other, but early studies suggest Caucasians may be most at risk. There also does not appear to be a genetic component, as the disease doesn’t seem to occur in more than one person in any family.
Causes of Susac’s Syndrome
The exact cause of SuS is unknown. Researchers are also unclear as to why the small vessels in the brain, retina, and inner ear are primarily affected. The symptoms of SuS are caused by damage to small blood vessels and the decreased ability of these blood vessels to carry blood and oxygen to the brain, eyes and ears.