CLINICAL CHARACTERISTICS OF ACUTE ENCEPHALOPATHY OF OBSCURE ORIGIN: BIPHASIC CLINICAL COURSE IS A COMMON FEATURE IN NON-SPECIFIC SUBTYPE

Objectives: To investigate clinical characteristics of acute encephalopathy of obscure origin (AE).

Methods: AE was defined as acute onset of consciousness disturbance without evidence of known cause. We reviewed the medical records of patients aged 1 month to 16 years who suffered AE from 1990 to 2005. Early clinical symptoms, laboratory findings, neuroimaging findings, and prognosis were investigated.

Results: 31 patients were identified during the past 18 years. 19 patients were diagnosed with specific subtypes of AE: RS in 6, ANE in 4, HSE in 3, AERRPS in 2, and HH in 4. Other 12 patients were separated into a non-specific AE group. Patients with specific subtypes (RS, ANE, HSE, and HH) frequently showed early CT or MRI abnormalities (11/16) and significant elevation of liver enzymes (11/17). Prognoses were extremely poor with early death in 7 patients and severe neurological sequelae in 6. Most non-specific AE patients showed biphasic clinical courses with initial prolonged or repetitive seizures and clinical exacerbation 2 to 5 days after onset (11/12), while specific AE patients did rarely (2/19). In patients with non-specific AE, neuroimaging abnormalities were rarely observed during the acute phase (1/12) but were highly detectable at clinical exacerbation (9/12). None showed severely abnormal elevation in liver enzymes. Three patients showed severe neurological sequelae.

Conclusion: Clinical characteristics of non-specific AE were biphasic clinical course, negative findings on early neuroimaging study, often normal in liver enzymes, and low mortality.