Predictive indicators for the development of epilepsy after acute encephalopathy with biphasic seizures and late reduced diffusion

Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) is a newly defined clinicoradiologic syndrome characterized by biphasic seizures and altered consciousness followed by restricted diffusion in the white matter on magnetic resonance imaging in acute phase. Intractable epilepsy commonly occurs as the late complication. This study aimed to search predisposing factors to the development of epilepsy after AESD. Consecutively treated 22 patients with AESD in our institution from 2006 to 2016 were grouped into those with post-encephalopathic epilepsy (PEE, n = 10) or without PEE (n = 12). There was no difference between two groups in age at the onset of AESD, duration of the initial seizures, or the follow-up periods after discharge. PEE group patients more frequently showed coma or involuntary movements during the course of AESD than non-PEE group patients (36% vs. 8%, p = 0.008). The quantitative analysis of apparent diffusion coefficient (ADC) map revealed that PEE group showed broader areas with reduced diffusion in the posterior lobes at the onsets of AESD than non-PEE group (0.113 vs. 0.013, p = 0.035). On the other hand, the atrophy on day 30-ADC map did not correlate with the development or control of epilepsy. These results suggest that the clinical severity and ADC profiles in acute phase, rather than the brain atrophy in convalescent phase, may predict the development of post-AESD epilepsy.