Makindo Medical Notes

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

In the differential diagnosis of hearing loss and reduced vision, particularly in young female patients, Susac's syndrome should be considered. Examination findings should readily distinguish this condition from others. Physicians should look for the classical triad of 1) hearing loss, 2) branched retinal artery occlusions (BRAOs), and 3) encephalopathy.

Introduction

• First described by John O. Susac in 1979.
• An unusual acute autoimmune neurological syndrome.
• A rare microangiopathy involving the brain, retina, and cochlea, predominantly affecting young women.

The Classical Triad

• Subacute encephalopathy.
• Retinal arteriolar branch occlusions (BRAOs).
• Sensorineural hearing loss.

Aetiology

• Microangiopathy with microinfarctions in the cochlea, retina, and encephalic tissues.
• Predominantly affects the corpus callosum.
• Anti-endothelial cell antibodies may play a role.

Clinical Features

• Headache, memory loss, personality changes, delirium, and confusion.
• Ataxia, encephalopathy, seizures, and migrainous headaches.
• Acute visual loss due to branch retinal artery occlusions.
• Asymmetric bilateral sensorineural hearing loss, reflecting microinfarctions in the cochlear apex.
• Self-limited, fluctuating, and monophasic course, potentially worsening during pregnancy.
• Typically lasts 2-4 years, though durations vary.

Investigations

• Blood tests (FBC, U&E, CRP) are often normal.
• CSF: Elevated protein levels may be detected.
• MRI:
  • Classic changes in the central corpus callosum, with small, multifocal lesions.
  • Acute lesions enhance in 70% of cases; leptomeningeal enhancement in 33%, deep grey matter involvement in 70%.
  • Characteristic "snowball" lesions, "string of pearls" in the corpus callosum, or "spoke" lesions touching the callosal roof.
• Fluorescein Angiography: Diagnostic for BRAOs.
• Audiogram: Detects sensorineural hearing loss, often bilateral low-frequency loss with normal high frequencies, reflecting microinfarctions in the cochlear apex.

Imaging

Differential Diagnoses

• Atypical Multiple Sclerosis (MS) or Acute Disseminated Encephalomyelitis (ADEM).
• CADASIL, SLE, Antiphospholipid Syndrome (APL), or Vasculitis.
• Neuro-Behçet's disease.
• Lymphoma or temporal arteritis.
• Cogan's syndrome or cerebral vasculitis.

Management

• No definitive treatment; consider targeting T and B cells:
  • IV Methylprednisolone, Azathioprine, Rituximab, Mycophenolate, IVIG, or plasmapheresis during active disease.
• Intratympanic dexamethasone injections during the acute phase of hearing loss may offer transient relief.
• Serial monitoring with audiometry, fluorescein angiography, and MRI to assess disease progression and treatment response.
• Most patients recover, though the course may fluctuate and require close follow-up.

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