Encephalitis: We need to take a closer look

Abstract

Encephalitis is a syndrome caused by many pathogens as well as non-infectious causes. Presenting symptoms are fever, altered consciousness, behavioral changes or psychosis and seizures with or without associated weakness or tract symptoms. It is a neglected entity and under-reported. Official statistics of encephalitis in Thailand (population of 70 millions) revealed approximately 500 cases [431(2010) and 566 (2011)]. After bacterial, parasitic and known viruses have been excluded, approximately half remain as unknown etiology even at sophisticated centers. During 2011, there were 84 patients with clinically, CSF and neuroimaging findings consistent with viral encephalitis admitted to Chulalongkorn Hospital. Several viral encephalitis cases had absence of CSF pleocytosis. Forty percent (34/84) had etiologies identified which included herpesviruses, Japanese encephalitis virus and dengue virus. Ten percent (8/84) were initially misdiagnosed. As many as 19% (16/84) had acute disseminated encephalomyelitis (with predominant involvement of white matter), and those of other immune etiologies (such as, anti-NMDA, -ANNA-2, -AMPA-2, -GABA, -VGKC). Their ages ranged between 3 and 90. Magnetic resonance imaging (MRI) of the brain, although helpful, had limitations in that one virus can present as many features. What is generally classified as typical MRI for this infection, may be seen in only half of the patients. This is particularly true in the case of herpes simplex encephalitis. New molecular technology may well reduce this unidentified number in the near future, but requires further research. Lack of identification may also be due to incorrect timing of sample collection of serum or CSF. Samples may contain insufficient nucleic acids. Furthermore, there may be an actual presence of novel viruses and of those which usually cause other organ infection (respiratory /gastrointestinal) but are also able to cause encephalitis. The problem with samples with insufficient nucleic acids can be overcome by whole transcriptome and whole genome amplification prior to PCR or high throughput next generation sequencing. More affordable PCR plate array platforms are being developed. Many cases of encephalitis are from agents that are shared between humans and animals. Epidemiological issues need to be considered when facing zoonoses. Preemptive measures in Thailand include bat and other wildlife surveillance of Nipah and other paramyxoviruses, corona-, calici- as well as lyssaviruses. When using a “One Health” approach, human and veterinary physicians as well as wildlife scientists cooperate and are able to develop more rapid effective control methods. Efforts are underway using analysis of clinical presentations and new imaging technology (such as diffusion tensor imaging), to identify features that suggest a specific etiology. This symposium will be composed of clinicians and scientists who will attempt to present an overview and encourage discussion of this complex subject.