The spectrum of acute encephalopathy with reduced diffusion in the unilateral hemisphere

Area of Science:

• Pediatric Neurology
• Neuroimaging
• Infectious Diseases

Background:

• Acute encephalopathy is a critical neurological condition in children.
• Unilateral hemispheric involvement can present unique diagnostic challenges.

Purpose of the Study:

• To describe the clinical, electroencephalogram (EEG), and magnetic resonance imaging (MRI) features of pediatric acute encephalopathy with unilateral hemisphere reduced diffusion.
• To identify potential etiological factors and neurological outcomes associated with this specific phenotype.

Main Methods:

• Retrospective review of seven pediatric patients diagnosed with reduced diffusion in the unilateral subcortical white matter.
• Analysis of clinical presentations, seizure characteristics, laboratory findings, EEG patterns, and MRI findings during acute and subacute phases.
• Virological confirmation of human herpesvirus 6 and 7 infections in a subset of patients.

Main Results:

• Seven patients (median age 32 months) presented with unilateral hemisphere reduced diffusion.
• Human herpesvirus 6 (2 patients) and 7 (1 patient) infections were identified.
• Initial symptoms included prolonged seizures (4), brief seizures (2), or delirious behavior (1).
• MRI revealed reduced diffusivity in the subacute phase, with normal findings in the acute phase.
• EEG showed variable degrees of slowing in the affected hemisphere.
• Six patients experienced neurological sequelae.

Conclusions:

• Reduced diffusion in the unilateral hemisphere represents a distinct phenotype of acute encephalopathy in children.
• Early recognition of this pattern on neuroimaging is crucial for diagnosis and management.
• Human herpesvirus infections are potential triggers for this condition.