Susac syndrome

David Goldemund M.D.
Updated on 29/02/2024, published on 18/02/2022

  • rare microangiopathy affecting the arteries of the brain, retina, and cochlea (retino-cochleo-cerebral dysimmune vasculopathy)
    • in partial forms of this syndrome, only 2 of the 3 components are clinically apparent. There are reports of subacute bilateral sensorineural hearing loss with bilateral retinal artery occlusion without apparent cerebral dysfunction
  • described by John Susac in 1979 (first reported in 1973)  (Pfaffenbach, 1973)
    • initially termed “small infarctions of cochlear, retinal, and encephalic tissues (SICRET)” syndrome or “retinopathy, encephalopathy, and deafness microangiopathy (RED-M)” syndrome
  • predominantly affects females (3:1) in the 2nd-4th decade (range 7-72 years), often associated with delivery
  • the exact cause is unknown; autoimmune microangiopathy or autoimmune coagulopathy (with APL positivity) are considered (Bucciarelli, 2014)
    • different pathogenetic mechanisms can cause the same clinical syndrome

Clinical presentation

  • most commonly monophasic, progressive course
  • brain dysfunction
    • acute or subacute encephalopathy (neuropsychiatric manifestations)
    • headaches
    • stroke
    • epileptic seizures
    • cranial neuropathies
  • sensorineural hearing loss, tinnitus, vestibular dysfunction
  • ocular symptoms
    • visual disturbances (visual field defects) – due to retinopathy (occlusion of the retinal artery or its branches – BRAO)
    • uveitis

Diagnostic evaluation

Brain imaging (MRI)

  • leukoencephalopathy with a tendency to involve the central corpus callosum
  • microinfarcts in the internal capsule – “string of pearls
  • specific lesions in the corpus callosum – “snowball lesions
  • grey matter involvement and leptomeningeal enhancement may be present (in ~ 30%)
    • such findings are useful in the DDx of MS and ADEM
Susac syndrome - "snow balls" in corpus callosum
Susac syndrome - "string of pearls" in internal capsule
Leukoencephalopathy in Susac syndom
Susac syndrome (FLAIR)

Ophthalmological examination

  • widefield fluorescein angiogram can show artery occlusion
    • peripheral branch retinal artery occlusion (BRAO)
    • segmental vessel wall increased fluorescence/leakage, capillary dropout, peripheral nonperfusion, and peripheral capillary changes
  • look for signs of uveitis

Laboratory tests

  • CSF
    • oligoclonal bands are commonly absent
    • sporadic lymphocytic pleocytosis or elevated CSF protein may occur
  • CBC: occasional monocytosis or eosinophilia
  • mild elevation of serum antinuclear and/or antiphospholipid antibodies

Diagnostic criteria

Suspected Incomplete Complete
1 symptom 2 symptoms complete clinical triad (approx 13%)
absence of significant vascular risk factors (atherosclerosis and/or coagulopathy)
+ one of the following risk factors:

  • female between 20-40 years of age
  • female within 1 year of pregnancy
  • presence of characteristic corpus callosum or periventricular lesions on MR

Differential diagnosis


  • treatment of Susac syndrome must be aggressive and sustained to control symptoms and prevent further brain damage and vision loss
  • the mainstay of treatment is immunosuppressive therapy
    • for long-term treatment, combine steroids with, e.g., AZATHIOPRINE
      • IVIG, methotrexate and mycophenolate mofetil are other options
    • in patients whose symptoms progress despite this treatment, add either  RITUXIMAB or  CYCLOPHOSPHAMIDE
  •  antiplatelet therapy (commonly aspirin or clopidogrel)

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Susac syndrome