Acute encephalopathy with biphasic seizures and late reduced diffusion; posterior frontal hyperperfusion before late seizures revealed by arterial spin labeling: A case report.

Background: Arterial spin labeling, a magnetic resonance imaging modality that can evaluate cerebral perfusion without using a contrast material or ionizing radiation, is becoming increasingly accessible. However, only a few reports have used this method to assess the perfusion abnormalities observed in acute encephalopathy with biphasic seizures and late reduced diffusion.

Patient Description: A 10-month-old Japanese girl presented with febrile status epilepticus (early seizures). Her convulsions ceased after the administration of intravenous phenobarbital, although her impaired consciousness was protracted. Five days later, diffusion-weighted imaging revealed slightly high signal intensity lesions in the bilateral posterior frontal areas. Arterial spin labeling revealed bilateral frontal-dominant hypoperfusion and posterior frontal hyperperfusion. On day 6, she had three convulsions (late seizures) and was diagnosed with acute encephalopathy with biphasic seizures and late reduced diffusion. She received treatment accordingly and recovered eventually.

Discussion: Based on previous reports, hypoperfusion within 1-2 days of early seizures and hyperperfusion accompanied by bright tree appearance on diffusion-weighted imaging within 1-2 days of late seizures are typical in acute encephalopathy with biphasic seizures and late reduced diffusion. In our patient, the first magnetic resonance imaging scan was performed one day prior to the onset of late seizures. We observed posterior frontal hyperperfusion accompanied by high signals on diffusion-weighted imaging, which leads us to speculate that this could be a predictive marker of late seizures.