Delirium as presentation of late-onset and relapsing Susac syndrome

A 67-year-old patient, only known for bilateral presbycusis, presented with subacute onset of delirium. Clinical examination showed multifocal neurological deficits, all together suggesting subcortical frontal dysfunction together with cerebellar and corpus callosum involvement.Cerebral MRI demonstrated supratentorial and infratentorial subcortical and periventricular T2-hyperintense lesions with cerebellar gadolinium enhancement and multiple central lesions of the corpus callosum (snowball lesions). The diagnosis of Susac syndrome was made and the patient treated with intravenous methylprednisolone, followed by a prednisone maintenance dose over 8 weeks. After a clinical improvement, a relapse was noticed during corticosteroid tapering. The patient was again treated with intravenous methylprednisolone followed by a prednisone maintenance therapy with simultaneous introduction of mycophenolate mofetil acid and one cycle of intravenous rituximab. The patient recovered rapidly. At 11-month follow-up, only mild executive dysfunction and persistent right postural tremor was noted, MRI showed partial regression of subcortical and juxtacortical lesions.