Acute disseminated encephalomyelitis with severe neurological outcomes following virosomal seasonal influenza vaccine

Abstract

Acute disseminated encephalomyelitis (ADEM) is an inflammatory, usually monophasic, immune mediate, demyelinating disease of the central nervous system which involves the white matter. ADEM is more frequent in children and usually occurs after viral infections, but may follow vaccinations, bacterial infections, or may occur without previous events. Only 5% of cases of ADEM are preceded by vaccination within one month prior to symptoms onset. The diagnosis of ADEM requires both multifocal involvement and encephalopathy and specific demyelinating lesions of white matter. Overall prognosis of ADEM patients is often favorable, with full recovery reported in 23% to 100% of patients from pediatric cohorts, and more severe outcome in adult patients. We describe the first case of ADEM occurred few days after administration of virosomal seasonal influenza vaccine. The patient, a 59-year-old caucasic man with unremarkable past medical history presented at admission decreased alertness, 10 days after flu vaccination. During the 2 days following hospitalization, his clinical conditions deteriorated with drowsiness and fever until coma. The magnetic resonance imaging of the brain showed multiple and symmetrical white matter lesions in both cerebellar and cerebral hemispheres, suggesting demyelinating disease with inflammatory activity, compatible with ADEM. The patient was treated with high dose of steroids and intravenous immunoglobulin with relevant sequelae and severe neurological outcomes.

Keywords: ADEM; acute disseminated encephalomyelitis; adverse event; influenza vaccination; virosomal vaccine.

Figure 1. Axial T2 encephalic magnetic resonance (A and B), coronal FLAIR (C), and sagittal T1 post Gd (D) sequences demonstrated: multiple white matter focal lesions located in cerebral and cerebellar hemispheres, predominantly symmetric and cortico-medullary. These lesions are hyperintense on FLAIR, DWI sequences (some of them with increased ADC) with contrast enhancement of larger lesions.

Figure 2. AxialT2encephalic magnetic resonance (A and B), coronal T1 post Gd (C) sequences performed about 1 mo after clinical onset of symptoms and after therapy: supratentorial and infratentorial demyelinating lesions were unchanged with overall dimensions slightly reduced and negative enhancement.