ACUTE INFANTILE ENCEPHALOPATHY PREDOMINANTLY AFFECTING THE FRONTAL LOBES (AIEF): A NOVEL CLINICAL CATEGORY AND DIAGNOSTIC CRITERIA

Objectives: To establish the diagnostic criteria for acute infantile encephalopathy predominantly affecting the frontal lobes (AIEF), a novel form of acute encephalopathy in infancy.

Methods: Clinical data were collected from 15 patients who were seen by us and diagnosed as having AIEF, and 2 patients previously reported in the literature.

Results: The mean age of onset was 1 year and 7 months. Boys and girls were equally affected. There was always an association with hyperpyrexia due to viral illness. Manifestations at the onset were convulsive status epilepticus and prolonged coma, followed by signs of frontal lobe dysfunction such as a lack of spontaneity and regression of verbal functions. Imaging studies demonstrated edematous changes of the bilateral frontal lobes, which showed increased perfusion initially and attenuated perfusion subsequently. The recovery of intellectual deficit was generally slower compared with that of motor disability.

Conclusion: Based on these findings, we propose tentative diagnostic criteria of AIEF as follows: 1) Acute encephalopathy in infancy and early childhood following a febrile illness due to a viral infection: convulsive status epilepticus and prolonged impairment of consciousness. 2) Neurological manifestations suggesting frontal lobe dysfunction: a lack of spontaneity and regression of verbal functions which become evident after the recovery of consciousness. 3) Radiological features showing selective involvement of the cerebral cortex predominantly distributed in the frontal lobes: edematous changes as well as increased perfusion at the onset, followed by attenuation of cerebral perfusion and mild atrophic changes in the frontal lobes. 4) Absence of laboratory and radiological findings for infectious or inflammatory disorders of the brain and systemic metabolic disorders.