Susac syndrome

Findings

Figure 1 and Figure 2: FLAIR images reveal multiple punctate T2 signal hyperintensities in the cortical, subcortical white matter and bilateral centrum semiovale.
Figure 3: Coronal T2 weighted image demonstrates a focus of abnormal T2 signal in the of the corpus callosum (yellow arrow).
Figure 4: Axial T1 post contrast image demonstrates punctuate enhancement of lesions within the centrum semiovale.

Differential diagnosis
- Susac syndrome
- Multiple sclerosis (MS)
- Acute disseminated encephalomyelitis (ADEM)
- Transient ischemic attacks
- Systemic vasculitis
- Thrombophilic disorders
- Mitochondrial encephalopathy


Diagnosis: Susac syndrome


Susac syndrome is a rare microangiopathy characterized by a clinical triad of encephalopathy, branch retinal artery occlusions, and hearing loss. The syndrome predominantly affects women in their third and fourth decades of life, between the ages 18 and 42. Though the exact pathogenesis of this disorder is unknown, the findings of retinal microangiopathy and brain biopsies suggest a small vessel vasculitis leading to arteriolar occlusion and microinfarction of cerebral, retinal and cochlear tissue.

If a patient with a history of acute encephalopathy also develops hearing loss or acute visual loss, Susac syndrome should be considered.

The neuroimaging study of choice is the MRI, which typically demonstrates a pattern of punctuate, multifocal supratentorial lesions. The disease invariably involves the corpus callosum and affects both white and grey matter. Leptomeningeal enhancement may occur.

Multiple sclerosis (MS) and acute disseminated encephalomyelitis (ADEM) can mimic the MRI changes seen in patients with Susac syndrome. However, the callosal lesions in Susac syndrome are centrally located while patients with MS and ADEM typically have lesions involving the undersurface of the corpus callosum. Deep gray matter involvement commonly occurs in ADEM but is very rare in MS. Leptomemingeal involvement is not typical of either MS or ADEM. Demyelination is not a typical feature of Susac syndrome.

Treatment currently consists of intravenous methylprednisolone, followed by oral steroids in conjunction with the use of intravenous immunoglobulin (IVIG). The condition is typically self limiting, but can take up to five years to resolve.