Suspected acute encephalopathy with symmetrical abnormal signal areas in the basal ganglia, thalamus, midbrain and pons diagnosed by magnetic resonance imaging.

A 4-year-old boy was admitted with disturbed consciousness following a convulsion. He developed bilateral pyramidal tract signs and showed a decerebrate posture. Laboratory findings revealed severe liver dysfunction and disseminated intravascular coagulation. On the eighth day eight in hospital he developed parkinsonism. However, 5 months from onset he had recovered almost completely. Brain CT on admission showed low density areas in the basal ganglia, thalamus, midbrain and pons. A T2-weighted scan in magnetic resonance imaging (MRI) showed almost symmetrical high signal intensities in both basal ganglia (including putamen, caudate nucleus, globus pallidus), external capsule, internal capsule thalamus, midbrain, pons and white matter of the peribasal ganglia; but a T1-weighted scan showed low signal intensities in the same regions during all phases. Therefore hemorrhagic lesions or the presence of thalamic methemoglobin were excluded. It was considered that the pathogenesis may be cytotoxic cellular edema due to cytotoxic agents or acute metabolic factors. Clinical presentation, laboratory findings and radiological findings were most suggestive of acute necrotizing encephalopathy. As differential diagnoses, acute disseminated encephalomyelitis and brainstem encephalitis were considered.