Acute necrotizing encephalopathy with H1N1 virus infection in a child.

A 7-year-old man presented to our radiology unit with high fever, generalized tonic-clonic type seizures, and neurological deterioration requiring intensive care. Cerebrospinal fluid analysis showed increased protein (94 mg/dL) and normal glucose (41 mg/ dL) levels. An initial brain magnetic resonance imaging (MRI) revealed symmetrical and expansile hyperintense lesions in the bilateral thalami and external capsules (Figure 1A and 1B). Restricted diffusion patterns of the involved brain regions were detected (Figure 1C and 1D). These radiological imaging findings suggested acute viral encephalitis, compatible with acute necrotizing encephalopathy (ANEC). Real-time polymerase chain reaction test performed with samples from nasopharyngeal swabs was positive for influenza A virus (H1N1). Therefore, ANEC-associated H1N1 virus infection was diagnosed. The patient underwent antiviral, anticonvulsant, and anti-inflammatory therapy. Fifteen days after therapy, a follow-up brain MRI revealed a decrease in signal intensity in the extent of lesions involving the bilateral thalami and external capsules with decreases in diffusion restriction patterns (Figure 2).