Background Each year many children suffer from respiratory infections caused by Influenza A virus, but only a limited number experiences severe complications. One of these serious complications is an acute necrotizing encephalopathy (ANEC).

Methods We report two cases of patients with ANEC following upper airway infection. Both children were referred to our paediatric intensive care unit (PICU) due to rapid neurological deterioration and respiratory failure. None had received vaccination against influenza. A 16-year old boy presented with difficulties in speech and motor deficits. A 14-months old girl had multiple focal seizures. Her Glasgow-Coma-Scale was 4 on admittance to PICU.

Both patients received a MRI (Magnetic Resonance Imaging) of the brain. The MR imaging findings demonstrated abnormal signal intensity bilaterally in multiple cortical and subcortical regions. In both cases Influenza A was detected on a nasopharyngeal swab by using polymerase chain reaction assay.

Results Both patients were treated with oseltamivir without notable clinical improvement. The boy showed complete reconvalescence. The girl suffered from increased intracranial pressure within hours after hospital admittance needing urgent external cerebrospinal fluid drainage. Her condition was complicated by an acute respiratory distress syndrome requiring mechanical ventilation. Meanwhile her consciousness has dramatically improved, but we still expect neurological sequelae.

Conclusion To our knowledge severe complications following an infection with influenza are rare but have to be kept in mind when treating a child with respiratory infection and neurological impairment. The insufficient response to oseltamivir underlines the need to re-evaluate the benefit of vaccination against influenza in children.