Cases of prolonged mild disturbance of consciousness and acute encephalopathy.

Background Acute encephalopathy (AE) is defined by the Japanese guidelines as the acute disturbance of consciousness (Glasgow coma scale [GCS] score <= 11) that persists for >24 h. We have often encountered, however, cases of prolonged mild disturbance of consciousness (PMDC) with GCS score >11, meaning that they do not fit the guideline definition of AE. The reports of these cases have been relatively sparse, and the nosological position, prognosis, and other characteristics remain unknown. To clarify the characteristics of PMDC we compared cases of PMDC with cases of AE. Methods This study was a retrospective observational study at a tertiary children's hospital in Japan. We studied children with a diagnosis of AE or PMDC between January 2011 and August 2016. Results Thirteen cases of PMDC and 19 cases of AE were identified during the study period. PMDC patients more frequently had hyponatremia (P < 0.01), paradoxical arousal response on electroencephalogram (P = 0.010), normal computed tomography (CT; P = 0.025), and normal magnetic resonance imaging (MRI; P < 0.01) than the AE patients. Sequelae were more frequently observed in AE than in PMDC patients (P = 0.011). Conclusions PMDC has different characteristics to AE with regard to hyponatremia, paradoxical arousal response, CT or MRI findings, and prognosis. Despite the differences, PMDC might also be regarded as being a milder member of the wide variety of AE and related diseases.