A 52-year old man was admitted for status epilepticus and encephalitis following 3 days of upper respiratory symptoms. He was febrile to 39°C. Cerebrospinal analysis showed 10 WBC, protein 194, glucose 78, and elevated IgG synthesis rate with no oligoclonal bands. Infectious and autoimmune workup in the serum and CSF was unremarkable. Brain MRI demonstrated multifocal well-defined T2-hyperintense lesions, with subtle gadolinium enhancement, and blood products on susceptibility weight imaging. Nasal swab polymerase chain reaction returned positive for influenza A, H1N1 2009 strain. A diagnosis of AHLE or acute necrotizing encephalopathy (ANE) associated with influenza was made. He was treated with oseltamivir and corticosteroids with significant improvement in his mental status. At 3-month follow-up he had returned to baseline, and MRI demonstrated dramatic improvement in prior lesions.

Prior reports of AHLE associated with H1N1 infection have largely reported devastating neurologic outcomes. Despite evidence of hemorrhage on our patient’s MRI suggestive of AHLE, our patient responded favorably to treatment. Our case suggests that H1N1 associated AHLE may have a more diverse spectrum than typical acute fatal cases in a predominant pediatric population.