Clinical characteristics of acute encephalopathy with acute brain swelling: A peculiar type of acute encephalopathy

Abstract Objectives Acute encephalopathy has been observed with acute brain swelling (ABS) that is characterized by rapid progression to whole-brain swelling. The objective of this study was to describe the clinical characteristics of ABS. Methods We encountered four patients with ABS and retrospectively investigated their clinical data with a medical chart review. Results Three patients had seizure clustering or status epilepticus in the clinical course. Signs of elevated intracranial pressure (ICP) appeared 3–9 h after the first convulsive attack in three patients. In all patients, signs of brainstem involvement appeared 1–8 h after signs of elevated ICP. Mild hyponatremia that progressed after signs of elevated ICP appeared was noted in three patients. Brain CT revealed mild brain swelling in the initial phase, which rapidly progressed to whole-brain swelling. No focal abnormalities were detected on brain MRI in one patient. Continuous electroencephalography was initially normal, but in two patients, high-amplitude slow waves appeared with rapid changes before signs of brainstem involvement. Although recovery was achieved without sequelae in two patients, outcome was fatal for the other two. Conclusions The pathogenesis of ABS has yet to be clarified, but clinical features in our patients are not consistent with any established subtypes of acute encephalopathy. Therefore, we believe that ABS should be recognized as a new type of acute encephalopathy.