Morbidity, mortality high in paediatric flu-associated acute necrotizing encephalopathy

Influenza-associated acute necrotizing encephalopathy (ANE) carries increased morbidity and mortality in children, according to a case series.

The case series included 41 children (median age 5 years, 56.1 percent female) with acute encephalopathy with radiologic evidence of acute thalamic injury and laboratory confirmed influenza infection. Researchers examined presenting symptoms, vaccination history, laboratory and genetic findings, interventions, and clinical outcomes.

Outcomes included modified Rankin Scale score (0: no symptoms; 1-2: mild disability; 3-5: moderate to severe disability; 6: death), length of stay, and functional outcomes.

Of the patients, 31 (76 percent) had no significant medical history, and five (12 percent) were medically complex. A total of 38 patients (93 percent) presented with fever, 41 (100 percent) with encephalopathy, and 28 (68 percent) with seizures. Thirty-nine patients (95 percent) had influenza A, and two had influenza B.

Laboratory findings included elevated liver enzymes in 78 percent of patients, thrombocytopenia in 63 percent, and elevated cerebrospinal fluid protein in 63 percent. In the subset of 32 patients (78 percent) who underwent genetic testing, 15 (47 percent) had genetic risk alleles potentially related to the risk of ANE, including 11 (34 percent) with RANBP2 variants.

Notably, only six of 38 patients (16 percent) with available vaccination history had received age-appropriate seasonal influenza vaccination. Most patients received multiple immunomodulatory treatments, including methylprednisolone (95 percent), intravenous immunoglobulin (66 percent), tocilizumab (51 percent), plasmapheresis (32 percent), anakinra (5 percent), and intrathecal methylprednisolone (5 percent).

The median intensive care unit stay was 11 days, while the median hospital stay was 22 days. Death occurred at a median of 3 days after symptom onset in 11 patients (27 percent), primarily due to cerebral herniation (91 percent). Among the 27 survivors with 90-day follow-up, 63 percent had at least moderate disability (modified Rankin Scale score ≥3).

The findings highlight the importance of prevention, early recognition, intensive treatment, and standardized management protocols in this population.