Influenza B-associated acute necrotizing encephalopathy of childhood: a report from North America.

Central nervous system manifestation of influenza virus infection can be meningitis, encephalitis, or encephalopathy. Newland et al. [1] reported the incidence of influenzarelated neurologic complications as approximately four cases per 100,000 child-years in a geographical area of North America. Seizures were the most common presentation in this cohort with small number of patients with encephalopathy, post-infectious encephalopathy, stroke secondary to hypotension, and aseptic meningitis. Encephalopathy is characterized by absence of inflammation in the brain and composed of several subtypes such as acute necrotizing encephalopathy (ANE), Reye’s syndrome, and hemorrhagic shock and encephalopathy. Though, ANE is frequently reported from Far East countries, less than 10 cases were reported from western countries. A 3-year-old boy, with history of prematurity and very mild spastic diplegia, presented with mental status changes and posturing. He had low-grade fever and sore throat for 1 day, but at the presentation, he had a rapidly progressive neurologic deterioration with unresponsiveness and eye deviation that progressed to prominent extensor posturing. There was no family history of consanguinity, recurrent infections, immune deficiency or early infant deaths. His immunization was up-to-date. Vitals were following: temperature 101 F, heart rate 120, respiratory rate 44, blood pressure 117/60, and pulse oximetry 92 %. Due to subsequent poor respiratory effort, he was sedated and intubated in the emergency department. Neurologic examination was limited due to sedation, but sluggishly reacting symmetric pupil, facial symmetry, baseline increased tone of lower extremities could be appreciated. Tendon reflexes were 2? and bilateral positive Babinski’s reflex was noted. Extensive laboratory investigations were done and significant positive findings were: throat swab positive for influenza B by PCR, white blood cells 3.5 K/ll (normal range 6–17 K/ll), lymphocyte 60 % (50–56 %), magnetic resonance imaging (MRI) brain revealed prominent and fairly symmetrical T2/FLAIR signal abnormalities in the cerebellar peduncles, thalamus, midbrain and pons, and to a lesser extent in the left caudate (Fig. 1). MR spectroscopy did not reveal a prominent lactate peak. Cerebrospinal fluid (CSF) exam revealed 0 (normal 0–5/L) white blood cell, 0 red blood cells, protein 67 (normal 20–70 mg/dL) and glucose 137. Liver enzymes were significantly elevated: AST 750 (normal 20–60 U/L), ALT 2683 (normal 5–45 U/L), but coagulation parameters, bilirubin 0.3 (0.2–1.4 mg/dL), and ammonia 16 (29–57 lmol/L) were normal. Electroencephalography monitoring had not revealed any seizure activity and was most consistent with sedated sleep. Lactic acid was not elevated. CSF was negative for influenza and other viral agents. Serological tests for other viral antibodies were negative also. He had a prolonged and complicated 6-week course in the hospital. He received broad spectrum antibiotic and antiviral coverage initially as well as intravenous immunoglobulin and steroid taper. At discharge, he was ambulatory up to 300 feet with a reverse rolling walker. He was able to remove and replace block on peg board and was getting intensive help from a speech therapist for oral motor skills and progressive swallow skills. His extreme agitation, during initial part of the admission, showed improvement. He was more spastic requiring daily & Debopam Samanta dsamanta@uams.edu