Unusual presentation of acute encephalopathy with biphasic seizures and late reduced diffusion in Miller–Dieker syndrome

Background: Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) is a unique subtype of acute encephalopathy that occurs in children. To date, there is no description of a patient with concurrent Miller–Dieker syndrome (MDS) and AESD. Case presentation: We present a case of 2-year-old girl with MDS, who was admitted for status epilepticus with a high fever, was diagnosed with AESD. She exhibited seizure for more than 1 h, which disappeared after administration of intravenous diazepam and phenobarbital. Brain magnetic resonance imaging (MRI), performed on the third day post-admission because she had not regained consciousness after the seizure ceased, showed abnormally high intensities in subcortical white matter, predominantly in the frontal areas on diffusion-weighted images (DWI). Acute encephalitis/encephalopathy was diagnosed based on electroencephalography (EEG) findings of diffuse high-voltage delta waves without seizure activity. Six days post-admission, frequent apneic episodes were observed, with oxygen desaturation due to clustered seizures. Although seizures disappeared with continuous intravenous midazolam, subclinical seizures were present in amplitude-integrated EEG (aEEG); these were suppressed by increasing the midazolam dose. Conclusion: This is the first report of AESD in a patient with MDS. Ther disturbance of consciousness was difficult to recognize because of severe motor and intellectual disabilities due to MDS. EEG aids the evaluation of consciousness in the acute phase, and aEEG can be helpful for monitoring and controlling subclinical seizures in the biphasic phase of AESD, especially patients with underlying neurological disorders.