Diagnosis, differential diagnosis and misdiagnosis of Susac syndrome

Abstract

BACKGROUND: Susac syndrome (SuS) is an inflammatory condition of the brain, eye and ear. Diagnosis can be challenging, and misdiagnosis is common. METHODS: Retrospectively review of the medical records of 32 adult patients from an Australasian cohort of SuS patients. RESULTS: An alternate diagnosis prior to SuS was made in thirty patients (94%) with seven patients receiving two or more diagnoses. The median time to diagnosis of SuS was 3 months (range 0.5-100 months). The commonest misdiagnoses were migraine in ten patients (31%), cerebral vasculitis in six (19%), multiple sclerosis in five (16%) and stroke in five (16%). Twenty-two patients were treated for alternate diagnoses, ten of whom had further clinical manifestations prior to SuS diagnosis. At presentation seven patients (22%) met criteria for definite SuS, nineteen (59%) for probable SuS and six (19%) for possible SuS. Six patients (19%) presented with brain-eye-ear involvement, fourteen with brain-ear (44%), six with brain-eye (19%) and six (19%) with only brain involvement. In patients with the complete triad of symptoms the median delay to diagnosis was 3 months (range 1-9 months) compared to 5.25 months (range 0.5-100 months) for patients with encephalopathy and ocular symptoms at presentation. CONCLUSIONS: SuS patients are frequently misdiagnosed at initial presentation, despite many having symptoms or radiological features that are red flags for the diagnosis. Delayed diagnosis can lead to patient morbidity. The varied ways in which SuS can present, and clinician failure to consider or recognize SuS, appear to be the main factors leading to misdiagnosis.