Be Alert to ALERD: Acute Leukoencephalopathy with Restricted Diffusion - Atypical Presentation of a Rare Case

Background: Acute leukoencephalopathy with restricted diffusion (ALERD) is a novel entity observed in children with acute encephalopathy. It is characterized by diffusion restriction on MRI, which can be the distinctive and sometimes the only imaging finding. Other routine MRI sequences may appear normal. ALERD can have infectious or noninfectious causes. In this case, we present a patient with infectious ALERD associated with Influenza B virus. Case Presentation: A 10-year-old male presented to the emergency room with a brief history of fever and cough, followed by altered sensorium. He was irritable and ataxic. Neck stiffness was elicited upon examination. An MRI of the brain showed extensive symmetric diffusion restriction in the periventricular and deep white matter, corpus callosum, posterior limb of the internal capsule, and cerebral peduncles of both cerebral hemispheres. Cerebrospinal fluid study, blood and urine toxicology panels were non-contributory. The respiratory panel test was positive for Influenza B. A diagnosis of infectious ALERD was made. Following treatment with steroids, intravenous immunoglobulin, anti-glutamate agents, and supportive measures, he showed clinical and radiological improvement. Conclusion: The reporting of ALERD has risen in recent years due to its increased detection using MRI. Diffusion weighted image plays the key role in the final diagnosis. Supportive care and prompt treatment of seizures are very important for better outcome. Follow-up imaging is also required to assess reappearance of white matter edema, development of cerebral atrophy or gliosis.