Encephalitis

Viral infection of the brain, or encephalitis, is characterised by impairment of cerebral function. In contrast, meningeal infection does not affect actual brain tissue. Epidemics occur seasonally in many parts of the world and are important causes of death and disability in the young and elderly. The equine encephalitides have recently caused widespread epidemics in South America. HSV is the most important cause of sporadic encephalitis worldwide, since it is treatable and should therefore be considered in all cases. However, Japanese encephalitis far outstrips HSV in actual numbers. Clinical features include high fever, headache, nausea and vomiting, followed by convulsions, confusion and changes in level of consciousness. Some patients also present with meningism, focal neurological signs, or abnormal behaviour. Severe cases result in prolonged coma, hemiparesis, dystonia, decorticate or decerebrate posturing, and respiratory failure. Neurological sequelae such as mental retardation, hemiparesis and behavioural abnormalities are particularly common after Japanese encephalitis, untreated HSV encephalitis, and post-infectious/vaccination encephalomyelitis. Our research, in collaboration with HTD and Paediatric Hospitals Number One and Two, seeks to understand the aetiology of encephalitis, improve the diagnostic yield from patients with encephalitis by molecular and classical means and, we hope, improve treatment of patients with this disease. We are also studying the role of the mosquito vector in Japanese encephalitis.

Bacterial Meningitis

An inflammation of the leptomeninges caused by infection of the cerebrospinal fluid (CSF) within the subarachnoid space around the brain and spinal cord, and the ventricular system. It is a medical emergency. Bacterial meningitis may be classified into spontaneous community acquired meningitis and post-traumatic meningitis following neurosurgery or traumatic brain injury. The most common causes of bacterial meningitis are Streptococcus pneumoniae, Neisseria meningitides, Haemophilus influenzae B, Mycobacterium tuberculosis and, in Vietnam, Streptococcus suis. Early clinical manifestations include non-specific malaise, apprehension or irritability, followed by fever, headache, myalgia and vomiting. Photophobia and disturbance of consciousness usually develop later. In older children and adults the symptoms most suggestive of meningitis are irritability, severe headache and vomiting, but in meningococcal infection, diarrhoea is a common non-specific symptom and the vasculitic rash is a crucial sign but may not be present very early in the illness. Any patient with headache and a rash should be suspected of having meningococcal meningitis and treated immediately. Almost all adults present with at least two of the classic symptoms of bacterial meningitis: headache, fever, neck stiffness and altered consciousness. Despite improvements in antibiotics the case fatality remains at 15-30% with neurological sequelae in a further 15-30% of patients. Co-infection with HIV can have a dramatic effect on the clinical presentation, the spectrum of bacterial infection and the patterns of drug resistance (local knowledge is essential in guiding rational therapy). Our research programme, in collaboration with HTD and Paediatric Hospital Number One and Two, HCMC, seeks to improve diagnosis, improve clinical care by undertaking randomized clinical trials, and by understanding the immunopathology of meningitis and the pharmacology of antibiotics used to treat meningitis.