Infantile Hypoxic Encephalopathy Mimicking Acute Encephalopathy with Biphasic Seizures and Late Reduced Diffusion (AESD) Identified as an Episode of Brief Resolved Unexplained Event (BRUE)

Acute encephalopathy with biphasic seizures and reduced diffusion (AESD) is characterized by biphasic seizures following febrile viral infections and delayed reduced diffusion of the cerebral white matter on magnetic resonance imaging (MRI) diffusion-weighted imaging (DWI) (bright tree appearance, BTA). However, hypoxic encephalopathy with biphasic seizures and AESD-mimicking imaging findings has not been reported. We report a case of hypoxic encephalopathy due to suffocation with concomitant biphasic seizures and BTA, mimicking AESD. On day 1, a healthy 5-month-old girl was found face down with decreased breathing and a deteriorating consciousness level, suggesting a brief resolved unexplained event (BRUE). Electroencephalography (EEG) revealed periodic epileptic discharges, suggesting possible nonconvulsive status epilepticus. Despite improvements in consciousness level and EEG abnormalities on day 2, her consciousness level deteriorated again with generalized tonic–clonic seizures on day 3, and a head MRI-DWI revealed restricted diffusion predominantly in the subcortical areas, suggesting BTA. Treatment for acute encephalopathy resolved the clinical seizures and EEG abnormalities. Persistence of abnormal EEG, reflecting abnormal excitation and accumulation of neurotoxic substances caused by hypoxia, may have contributed to the development of AESD-like findings. As hypoxic encephalopathy causes AESD-like biphasic seizures, monitoring consciousness level, seizure occurrence, and EEG abnormalities even after acute symptoms have temporarily improved following hypoxia is essential.