Acute Disseminated Encephalomyelitis: A Rare Complication Post Influenza Vaccination

Abstract

INTRODUCTION: Although rare, it should be recognized that certain vaccines can cause serious neurologic immunophenomena such as acute disseminated encephalomyelitis (ADEM). CASE PRESENTATION: A 83 year old Hispanic female was admitted with 2 days of altered mental status, weakness and fever. She had past medical history of hypertension,ischemic stroke and diabetes. She received inactivated influenza vaccine five days ago. On exam, she was obtunded, febrile with bilateral extensor plantar response and brisk reflexes. Computed tomogram of the head was unremarkable. Cerebrospinal fluid (CSF) analysis showed protein of 136 gm/dL, glucose of 108 gm/dL, with lymphocytic pleocytosis (44 cells/microliter). Broad spectrum antibiotics were started for presumed infectious meningoencephalitis. Her mental status declined further and she required mechanical ventilation. Magnetic resonance imaging (MRI) of the brain and spine showed diffuse white matter lesions involving periventricular white matter, thalamus, midbrain, dorsal brainstem, cerebellum and medulla oblongata (Figure A). CSF bacterial and fungal cultures, PCR for HSV, VZV, HHV-6, enterovirus, JC and BK viruses; anti-NMDA receptor antibody and flow cytometry for lymphoma were all negative. Serum studies for viral encephalitis, HIV and Quantiferon-TB were also negative. After exclusion of infectious and non-infectious causes, we made the diagnosis of post-vaccination ADEM based on the neurologic picture and MRI findings of extensive white matter changes along with recent influenza vaccination. DISCUSSION: ADEM is a rare inflammatory demyelinating disease of the central nervous system with an incidence of 0.4/100,000. Infection is the most common etiology; post-vaccination ADEM accounts for 5% of cases. However, ADEM that occurs after vaccination may not necessarily be attributable to the vaccine and might rather be a temporal association. In our patient, based on World Health Organization causality assessment criteria, post vaccination ADEM was «very likely». Daily methylprednisolone for 3-5 days followed by prednisone taper is the accepted first line therapy. Plasmapheresis is recommended for steroid unresponsive patients. With early treatment initiation, full recovery is seen in 50% to 75% of patients, within 1-6 months. Our patient did not respond to steroids and required plasmapheresis. She showed neurologic recovery with improved MRI (Figure 2) and was discharged to a rehabilitation facility on day 42. CONCLUSIONS: Clinicians should consider post-vaccination acute disseminated encephalomyelitis in patients with encephalopathy, multifocal neurological findings and recent vaccination after carefully excluding other causes.