Current Paediatrics (2000) 10, 110–115 © 2000 Harcourt Publishers Ltd doi: 10.1054/ cupe.2000.0095, available online at http://www.idealibrary.com on

Symposium: Infection

Management of viral meningitis and encephalitis

H. Lewis, F. M. Gibbon

KEY POINTS

VIRAL MENINGITIS

• Early identification and treatment of herpes simplex virus encephalitis can greatly reduce morbidity and mortality. • Exclude other treatable causes of acute encephalopathy. • Proven or suspected herpes simplex virus encephalitis should be treated with 14 days of intravenous acylcovir. • Polymerase chain reaction can provide a rapid and specific diagnosis for many viral infections of the CNS. • CT scan may be normal in first 5 days of viral encephalitis; MRI brain scan is the investigation of choice.

Most cases of viral meningitis worldwide occur in children and young adults.2 Viral meningitis has an incidence of 1.5 per 1000 children in the UK3 and is most common between the ages of 1 and 10 years. It is usually a benign, self-limiting disease from which 95% of children recover completely. Enteroviruses, especially echo and coxsackie viruses, are most often responsible for viral meningitis. In a review of aseptic meningitis in 274 children less than 2 years of age, the group B coxsackie virus and echovirus were aetiologic agents in 92% of cases.4 HSV1, varicella zoster, mumps and HIV are less commonly implicated. There is a seasonal variation, with peak incidence in summer and autumn coinciding with outbreaks of enterovirus infection.2

INTRODUCTION

Clinical features

In comparison with the prevalence of systemic viral infections, viral central nervous system (CNS) disease is uncommon.1 Viral invasion of the CNS is related to a breach in host defences rather than the virulence of the infecting virus. Thus, viral encephalitis and meningitis are usually caused by common pathogens such as herpes simplex virus (HSV) and enteroviruses. Certain viruses (e.g. enterovirus) preferentially infect the meninges, whilst others (e.g. HSV) infect brain parenchyma causing encephalitis, although considerable overlap exists.2 Most viral CNS infections are acquired by haematogenous spread.

Common clinical features regardless of the particular viral aetiology include: • Acute onset of fever and headache • Neck stiffness is present in 75% • Convulsions are rare in the absence of a preexisting seizure disorder • Neurological examination is usually normal • Deterioration in conscious level or seizures suggests a progression to encephalitis Clues regarding the specific viral aetiology may be obtained by an enquiry into systemic symptoms. For instance, myalgia and myocarditis suggest coxsackie virus, rashes and pharyngitis suggest enterovirus, and lymphadenopathy and orchitis suggest mumps. Enquiries should be made regarding travel, exposure to animals and insect bites, and exposure to toxins and drugs.

Hilary Lewis Specialist Registrar in Paediatrics Frances M Gibbon Consultant Paediatric Neurologist, Department of Child Health, University Hospital of Wales, Heath Park, Cardiff CF14 4XW, UK. Correspondence and requests for offprints to: FMG.

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Management of viral meningitis and encephalitis Table 1 Neuroimaging should be performed before a lumbar puncture in the following circumstances • • • • • • •

Impaired consciousness Cardiovascular instability Any of the signs of raised ICP Focal neurological signs Recent seizures (especially focal/prolonged) Coagulation disorder Retinal haemorrhage

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Table 2 Differential diagnosis of viral meningitis • Partially treated bacterial meningitis • Tuberculous meningitis (TBM) • Others Borrelia Mycoplasma Fungi Parasites e.g. toxoplasma Parameningeal infections SLE, sarcoidosis, Behc¸ et’s Toxins such as IKT3, isoniazid, AZT CNS tumours and leukaemia Kawasaki disease

Investigations Cerebrospinal fluid (CSF) examination is essential in order to confirm the diagnosis and should be carried out once raised intracranial pressure and the presence of a space occupying lesion have been excluded. Other contraindications to performing a lumbar puncture are shown in Table 1. Cell counts are in the range of 10–1000 leukocytes/mm3. Polymorphs may predominate early in the course of the illness with lymphocyte predominance occurring from 12 h. CSF protein is slightly raised at 0.5–1.0 g/l. CSF glucose is normal but may be mildly reduced with a CSF/serum glucose ratio