A case of acute encephalopathy with hyperperfusion detected by arterial spin labelling: Extending spectrum of acute encephalopathy with biphasic seizures and late reduced diffusion

Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) is the most common encephalopathy syndrome among Japanese children. We report, for the first time, a case of AESD, in which magnetic resonance imaging (MRI) showed no diffusion abnormalities, but hyperperfusion was detected by arterial spin labelling (ASL). A previously healthy Japanese 1-year and 5-month-old boy was transferred to our hospital due to a consciousness disorder after >60 min of status epilepticus on the first day of fever. Brain MRI on the first day revealed no abnormal findings. On the fourth day, focal seizures of the left upper and lower limbs were observed. Thereafter, the patient's condition progressed without seizures. Diffusion-weighted imaging (DWI) on day 6 showed no abnormal findings, including a bright tree appearance. However, ASL showed hyperperfusion in the frontoparietal lobes. MRI scans on days 19 and 39 revealed that the hyperperfusion lesions on day 6 had transitioned to hypoperfusion on ASL and displayed high signal intensity on T2-weighted and fluid-attenuated inversion recovery imaging. Cerebral atrophy was also observed. Based on the clinical course and imaging findings during the chronic phase, a diagnosis of AESD was made. ASL may be more sensitive than DWI for detecting AESD lesions and should be performed in children with suspected AESD.