Susac syndrome is a rare autoimmune disorder that causes inflammation of the small blood vessels, known as endotheliopathy. This condition primarily impacts the brain, retina, and inner ear. The immune system mistakenly attacks these healthy blood vessel cells, leading to swelling and reduced blood flow. This decreased blood supply can cause temporary dysfunction or permanent damage in the affected organs.
The Triad of Neurological, Vision, and Hearing Symptoms
Brain (Encephalopathy)
Brain involvement, or encephalopathy, often leads to neurological symptoms. Individuals commonly experience severe headaches, which can resemble migraines, sometimes accompanied by vomiting. Cognitive difficulties are also frequent, including confusion, disorientation, problems with short-term memory, slowed thinking, and reduced problem-solving abilities. Changes in personality or behavior, such as agitation or psychosis, can occur. Slurred speech (dysarthria) is another reported neurological symptom.
Eyes (Branch Retinal Artery Occlusions)
Visual disturbances arise from blockages in the small arteries of the retina, termed branch retinal artery occlusions (BRAOs). These occlusions can cause scotomas, which are blind spots or dark areas within the field of vision. Patients may describe seeing flashing lights or a “dark shade or curtain” covering part of their vision. Partial or complete loss of vision can occur in specific parts of the visual field, including peripheral vision.
Inner Ear (Sensorineural Hearing Loss)
Inner ear involvement leads to auditory and balance problems. A characteristic feature is sensorineural hearing loss, particularly affecting low frequencies. This hearing loss can be sudden in onset and may affect one or both ears. Tinnitus, described as a ringing or roaring sound in the ears, is a common accompanying symptom. Patients may also experience vertigo (dizziness and balance problems).
Other Common Manifestations
Beyond the defining triad, Susac syndrome can manifest with a broader range of symptoms. Psychiatric issues are frequently observed, encompassing significant changes such as anxiety, depression, paranoia, and, in some instances, hallucinations. These behavioral alterations can vary greatly in severity.
Problems with movement and coordination are also common. Patients may experience gait disturbances (difficulty walking steadily) and ataxia (lack of muscle coordination). Additionally, some individuals report constitutional symptoms, such as extreme fatigue or malaise. Muscle pain (myalgia) can also occur.
Diagnostic Processes to Identify Symptom Causes
Confirming a diagnosis of Susac syndrome involves a combination of specific tests that reveal characteristic abnormalities. Magnetic Resonance Imaging (MRI) of the brain is a primary diagnostic tool. MRI scans often show distinctive “snowball” lesions within the corpus callosum, a band of nerve fibers connecting the two brain hemispheres. Brain MRI may also reveal other white matter lesions, sometimes with contrast enhancement in acute phases, which represents ischemic strokes.
Fluorescein angiography, an ophthalmological test, visualizes blood flow in the retina. This test is highly effective in identifying branch retinal artery occlusions (BRAOs), which are blockages in the retinal arteries. It can show areas of arterial wall hyperfluorescence and leakage, even in areas without noticeable vision loss. An audiogram (hearing test) is performed to detect the specific pattern of sensorineural hearing loss. This typically reveals low-frequency hearing loss, although other frequencies can be affected. Diagnosis can be complex, as symptoms may overlap with other conditions like multiple sclerosis, making a comprehensive evaluation across specialties important.
The Course and Fluctuation of Symptoms
The progression of Susac syndrome is quite variable among individuals. The complete triad of symptoms may not be present at initial onset, potentially taking weeks, months, or even years to appear.
The disease can follow different patterns. Some patients experience a monophasic course, with a single episode of symptoms that eventually resolves, often within one to three years, particularly for brain involvement. Other patients may have a polycyclic, or relapsing-remitting, course, involving periods of symptom flare-ups followed by periods of improvement or remission. Symptoms can fluctuate in severity during these cycles. A less common pattern is chronic-continuous, where symptoms persist over a prolonged period, sometimes lasting three to ten years or even longer.