Hirai N, et al. - In order to assess the underlying pathomechanisms in patients with unclassified encephalopathy, brain metabolism by MR spectroscopy was evaluated. Findings suggested that excitotoxicity could be a common underlying pathomechanism of acute infectious encephalopathy, and prompt astrocytic neuroprotection from excitotoxicity could prevent progression of mild encephalopathy associated with excitotoxicity (MEEX) into acute encephalopathy with biphasic seizures and late reduced diffusion (AESD).