Susac's syndrome

Susac's syndrome (Retinocochleocerebral Vasculopathy) is a microangiopathy characterized by encephalopathy, branch retinal artery occlusions and hearing loss. It is caused by the immune system attacking healthy tissue, and can lead to mental disorders.

Description
Susac's Syndrome is named after Dr John Susac, who first described it in 1975. Sufferers often experience a personality change and develop bizarre and paranoid behaviour. Their speech can be affected, and many experience unrelenting and intense headaches and migraines, some form of hearing loss, and impaired vision. The problem usually corrects itself, but this can take up to five years. In some cases, subjects can become confused, and believe they are living in a time from their memory once again. According to Michael Hahn, a US Expert on the subject, thinking you live in a foreign country happens in a "fair percentage" of cases.

Only 201 people in the world are known to have Susac's Syndrome.

Treatment
There are a few case reports of the retinopathy due to Susac's disease responding to hyperbaric oxygen treatment with significant improvement of acuity. There is another report of the syndrome recurring after 18 years.(Pub Med reference). Treatment regiments proposed empirically include IVIG, high dose IV steroids. There are characteristic MRI saggital FLAIR appearances described in the radiologic literature.

Diagnosis
Radiographic Appearance: In a recent analysis (Susac et al., 2003), MRI images from 27 patients fulfilling the diagnostic criteria of Susac's syndrome were reviewed. Multifocal supratentorial lesions were present in all patients. Most lesions were small (3 to 7 mm), though some were larger than 7 mm. All 27 patients had corpus callosum lesions. These all had a punched-out appearance on follow up MRI. Though most commonly involving white matter, many patients also had lesions in deep grey matter structures (19 of 27), as well as leptomeningeal enhancement (9 of 27). Multiple sclerosis (MS) and acute disseminated encephalomyelitis (ADEM) can mimic the MRI changes seen in patients with Susac's syndrome. However, the callosal lesions in Susac's syndrome are centrally located. In comparison, 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.

Pathogenesis
In the March 1979 report in Neurology, Drs. Susac, Hardman and Selhorst reported two patients with the triad of encephalopathy, hearing loss and microangiopathy of the retina. The first patient underwent brain biopsy, which revealed sclerosis of the media and adventitia of small pial and cortical vessels, suggestive of a healed angiitis. Both patients underwent fluorescein retinal angiography that demonstrated multifocal retinal artery occlusions without evidence of embolic disease. 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. Demyelination is not a typical feature of Susac's syndrome. Muscle biopsies from such patients are usually normal, but some have also shown nonspecific signs of inflammation such as dense hyaline material surrounding endomysial capillaries. This suggests a possible systemic component of this disease, despite the predominance of central nervous system features.

Proposed causes include autoimmune vasculitis, hypercoagulable state and viral infection. Evidence for viral infection includes a prodromal illness in some patients. Development of symptoms during pregnancy and oral contraceptive use suggest a possible contribution of coagulation abnormalities in such patients. However, the relatively infrequent recognition of this syndrome has provided few cases for systematic study of possible causative factors.