Epidemiology: Most cases have been described in Japan and Taiwan but it has been seen worldwide.
Clinical features:
(1) The condition is primarily described in previously healthy children.
(2) The onset follows an infection, usually a viral infection such as influenza.
(3) The patient presents with an encephalopathy including an alteration in the level of consciousness.
(4) Other neurologic signs may develop including seizures, dystonia, etc.
(5) The CSF leukocyte count is typically low (<= 8 per µL).
(6) Imaging studies of the brain show symmetrical bilateral multifocal lesions in the thalamus, brainstem, tegmentum and cerebellum.
(7) Exclusion of other causes of encephalopathy.
The neurologic outcome is poor. If the patient survives then there is a high risk for some form of permanent neurologic sequelae.
