Recent studies have revealed that encephalitis lethargica (EL) may not be related to influenza virus infection but more likely to be a post-infectious autoimmune disease. The diagnostic clinical criteria for EL like illness include subacute hypersomnolence and ophthalmoparesis followed by Parkinsonism, oculogyric crisis, neuropsychiatric disorders and central respiratory abnormality. Recently, Magnetic Resonance Imaging (MRI), which depicts hypersignal intensity on T2 weighted, and FLAIR images at midbrain, tegmentum, and basal ganglia, have been very helpful diagnostic tests in EL like illness. Nevertheless, EL like illness has never been reported in Thailand. A 17 year-old man presented with hypersomnolence one week before admission. Physical examination revealed drowsiness and ophthalmoparesis. MRI showed bilateral hypersignal intensity lesions on T2 weighted and FLAIR images at midbrain, basal ganglia and temporal lobes. CSF studies showed normal profiles. CSF-PCR for herpes simplex virus, varicella zoster virus, cytomegalovirus, Epstein-Barr virus, Pan-Enterovirus and Westnile virus were negative. CSF Dengue and Japanese encephalitis virus hemagglutination test were negative. He was treated with intravenous dexamethasone and immunoglobulin.
Somnolence and ophthalmoparesis were improved. Two months later, he developed schizophreniform features and Parkinsonism. MRI revealed improvement of midbrain and basal ganglia lesions. CSF studies showed normal CSF profiles while oligoclonal bands were positive. Autoimmune profiles and serological tests for post-streptococcal infection as well as syphilis were negative. Thyroid function tests and serum ceruloplasmin were within normal limits. Levo-Dopa, clonazepam and sodium valproate had been prescribed and the clinical syndrome was gradually improved.

Keywords: Encephalitis lethargica, von Economo’s encephalitis, Magnetic Resonance Imaging, Oligoclonal
bands