Susac syndrome

Related Subjects: |Neurological History taking | Causes of Stroke | Ischaemic Stroke |Hypertension |CADASIL |CARASIL

In the differential diagnosis of hearing loss and reduced vision especially in a young female patient one should also be thinking of Susac's syndrome. Though examination should readily distinguish the two disorders, the physician should consider Susac's syndrome and look for the triad of 1) hearing loss, 2) branched retinal artery occlusions and 3) encephalopathy.

Introduction

• This syndrome was first described by John O. Susac in 1979
• Unusual an acute autoimmune neurological syndrome
• A rare microangiopathy of brain, retina, cochlea affecting mainly young women

The classical Triad

• Subacute encephalopathy
• Retinal arteriolar branch occlusions
• Sensorineural hearing loss

Aetiology

• Small microangiopathy with microinfarctions of cochlear, retinal and encephalic tissue
• Favours the corpus callosum
• Anti-endothelial cell antibodies

Clinical

• Headache, Memory loss, personality change, delirium, confusion
• Ataxia, Acute hearing loss, Encephalopathy, seizures, migrainous headache
• Acute visual loss - branch retinal artery occlusions
• Clinical course is usually self-limited, fluctuating, and monophasic which may worsen during pregnancy
• Lasts 2-4 years but can be longer or shorter
• Bilateral sensorineural hearing loss which is asymmetric and is thought to reflect sequelae of microinfarction in the apical cochlea

Investigations

• FBC, U&E, CRP may all be normal
• CSF protein can be elevated
• MRI changes involving central corpus callosum are classic. The lesions are typically small, multifocal, and frequently enhance during the acute stage (70%). Leptomeningeal enhancement was present in 33% and deep grey matter involvement (basal ganglia and thalamus) in 70%. Another article describes changes as Central callosal 'icicle' and 'spoke' lesions in contact with the roof of the callosum and a characteristic string of beads appearance of microinfarcts in the internal capsule have also been recognised. Also called “snowball” lesions in the corpus callosum. Supratentorial Lesions can resemble a "string of pearls".
• Fluorescein angiography: as BRAOs may be diagnostic
• Audiogram: may detect sensorineural hearing loss and should be done even if bedside hearing tests are normal. It may show bilateral low-frequency hearing loss, rising to normal at higher frequencies. This is the typical (cochlear) hearing loss seen and reflects microinfarction of the striae vascularis at the apex of the cochlea

Differentials

• Atypical MS/ADEM
• CADASIL/SLE/APL/Vasculitis
• Neuro-Behcet's disease
• Lymphoma, ADEM
• Cerebral vasculitis
• Temporal arteritis or Cogan's syndrome

Management

• Non proven but consider therapies that target both T and B cells - IV Methylprednisolone, Azathioprine, Rituximab, Mycophenolate, IVIG, Plasmapheresis until disease settles.
• Intratympanic injection of dexamethasone in the acute phase of hearing loss and tinnitus may provide transient benefit
• Serial audiometry, fluorescein angiography, and MRI to assess response and progression.
• Most make a recovery

References and further reading

• Rennebohm, R. M., Asdaghi, N., Srivastava, S., & Gertner, E. (2018). Guidelines for treatment of Susac syndrome - An update. International Journal of Stroke. https://doi.org/10.1177/1747493017751737
• New Developments in Susac's Syndrome
• Susac's Syndrome